Improve comments for surctionproof init+alloc/destroy funcs

The comments with 'XXX' was intended to indicate that the listed
concerns was subject to review and change, but the code with these
comments was merged straight away. This commit replaces comments
with more complete text describing the issues.

This also signifies that the commit that this code was introduced in is
not anymore 'work in progress'.

.gitignore

@@ -1,9 +1,11 @@
 bench_inv
 bench_ecdh
 bench_ecmult
+bench_generator
+bench_rangeproof
+bench_schnorrsig
 bench_sign
 bench_verify
-bench_schnorr_verify
 bench_recover
 bench_internal
 tests

.travis.yml

@@ -11,9 +11,11 @@ cache:
   - src/java/guava/
 env:
   global:
-    - FIELD=auto  BIGNUM=auto  SCALAR=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no  EXPERIMENTAL=no  JNI=no
+    - FIELD=auto  BIGNUM=auto  SCALAR=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no  EXPERIMENTAL=no  JNI=no GENERATOR=no RANGEPROOF=no WHITELIST=no
     - GUAVA_URL=https://search.maven.org/remotecontent?filepath=com/google/guava/guava/18.0/guava-18.0.jar GUAVA_JAR=src/java/guava/guava-18.0.jar
   matrix:
+    - SCALAR=32bit    FIELD=32bit       EXPERIMENTAL=yes RANGEPROOF=yes WHITELIST=yes GENERATOR=yes
+    - FIELD=64bit     EXPERIMENTAL=yes RANGEPROOF=yes WHITELIST=yes GENERATOR=yes
     - SCALAR=32bit    RECOVERY=yes
     - SCALAR=32bit    FIELD=32bit       ECDH=yes  EXPERIMENTAL=yes
     - SCALAR=64bit
@@ -65,4 +67,4 @@ before_script: ./autogen.sh
 script:
  - if [ -n "$HOST" ]; then export USE_HOST="--host=$HOST"; fi
  - if [ "x$HOST" = "xi686-linux-gnu" ]; then export CC="$CC -m32"; fi
- - ./configure --enable-experimental=$EXPERIMENTAL --enable-endomorphism=$ENDOMORPHISM --with-field=$FIELD --with-bignum=$BIGNUM --with-scalar=$SCALAR --enable-ecmult-static-precomputation=$STATICPRECOMPUTATION --enable-module-ecdh=$ECDH --enable-module-recovery=$RECOVERY --enable-jni=$JNI $EXTRAFLAGS $USE_HOST && make -j2 $BUILD
+ - ./configure --enable-experimental=$EXPERIMENTAL --enable-endomorphism=$ENDOMORPHISM --with-field=$FIELD --with-bignum=$BIGNUM --with-scalar=$SCALAR --enable-ecmult-static-precomputation=$STATICPRECOMPUTATION --enable-module-ecdh=$ECDH --enable-module-recovery=$RECOVERY --enable-module-rangeproof=$RANGEPROOF --enable-module-whitelist=$WHITELIST --enable-module-generator=$GENERATOR --enable-jni=$JNI $EXTRAFLAGS $USE_HOST && make -j2 $BUILD

Makefile.am

@@ -178,6 +178,30 @@ if ENABLE_MODULE_ECDH
 include src/modules/ecdh/Makefile.am.include
 endif
 
+if ENABLE_MODULE_SCHNORRSIG
+include src/modules/schnorrsig/Makefile.am.include
+endif
+
+if ENABLE_MODULE_MUSIG
+include src/modules/musig/Makefile.am.include
+endif
+
 if ENABLE_MODULE_RECOVERY
 include src/modules/recovery/Makefile.am.include
 endif
+
+if ENABLE_MODULE_GENERATOR
+include src/modules/generator/Makefile.am.include
+endif
+
+if ENABLE_MODULE_RANGEPROOF
+include src/modules/rangeproof/Makefile.am.include
+endif
+
+if ENABLE_MODULE_WHITELIST
+include src/modules/whitelist/Makefile.am.include
+endif
+
+if ENABLE_MODULE_SURJECTIONPROOF
+include src/modules/surjection/Makefile.am.include
+endif

configure.ac

@@ -129,13 +129,38 @@ AC_ARG_ENABLE(module_ecdh,
     [enable_module_ecdh=$enableval],
     [enable_module_ecdh=no])
 
+AC_ARG_ENABLE(module_schnorrsig,
+    AS_HELP_STRING([--enable-module-schnorrsig],[enable schnorrsig module (experimental)]),
+    [enable_module_schnorrsig=$enableval],
+    [enable_module_schnorrsig=no])
+
+AC_ARG_ENABLE(module_musig,
+    AS_HELP_STRING([--enable-module-musig],[enable MuSig module (experimental)]),
+    [enable_module_musig=$enableval],
+    [enable_module_musig=no])
+
 AC_ARG_ENABLE(module_recovery,
     AS_HELP_STRING([--enable-module-recovery],[enable ECDSA pubkey recovery module [default=no]]),
     [enable_module_recovery=$enableval],
     [enable_module_recovery=no])
 
+AC_ARG_ENABLE(module_generator,
+    AS_HELP_STRING([--enable-module-generator],[enable NUMS generator module [default=no]]),
+    [enable_module_generator=$enableval],
+    [enable_module_generator=no])
+
+AC_ARG_ENABLE(module_rangeproof,
+    AS_HELP_STRING([--enable-module-rangeproof],[enable Pedersen / zero-knowledge range proofs module [default=no]]),
+    [enable_module_rangeproof=$enableval],
+    [enable_module_rangeproof=no])
+
+AC_ARG_ENABLE(module_whitelist,
+    AS_HELP_STRING([--enable-module-whitelist],[enable key whitelisting module [default=no]]),
+    [enable_module_whitelist=$enableval],
+    [enable_module_whitelist=no])
+
 AC_ARG_ENABLE(external_default_callbacks,
-    AS_HELP_STRING([--enable-external-default-callbacks],[enable external default callback functions (default is no)]),
+    AS_HELP_STRING([--enable-external-default-callbacks],[enable external default callback functions [default=no]]),
     [use_external_default_callbacks=$enableval],
     [use_external_default_callbacks=no])
 
@@ -144,6 +169,11 @@ AC_ARG_ENABLE(jni,
     [use_jni=$enableval],
     [use_jni=no])
 
+AC_ARG_ENABLE(module_surjectionproof,
+    AS_HELP_STRING([--enable-module-surjectionproof],[enable surjection proof module [default=no]]),
+    [enable_module_surjectionproof=$enableval],
+    [enable_module_surjectionproof=no])
+
 AC_ARG_WITH([field], [AS_HELP_STRING([--with-field=64bit|32bit|auto],
 [finite field implementation to use [default=auto]])],[req_field=$withval], [req_field=auto])
 
@@ -175,6 +205,12 @@ else
     CFLAGS="$CFLAGS -O3"
 fi
 
+AC_MSG_CHECKING([for __builtin_popcount])
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[void myfunc() {__builtin_popcount(0);}]])],
+    [ AC_MSG_RESULT([yes]);AC_DEFINE(HAVE_BUILTIN_POPCOUNT,1,[Define this symbol if __builtin_popcount is available]) ],
+    [ AC_MSG_RESULT([no])
+    ])
+
 if test x"$use_ecmult_static_precomputation" != x"no"; then
   # Temporarily switch to an environment for the native compiler
   save_cross_compiling=$cross_compiling
@@ -230,6 +266,12 @@ else
   set_precomp=no
 fi
 
+AC_MSG_CHECKING([for  __builtin_clzll])
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[void myfunc() { __builtin_clzll(1);}]])],
+    [ AC_MSG_RESULT([yes]);AC_DEFINE(HAVE_BUILTIN_CLZLL,1,[Define this symbol if  __builtin_clzll is available]) ],
+    [ AC_MSG_RESULT([no])
+    ])
+
 if test x"$req_asm" = x"auto"; then
   SECP_64BIT_ASM_CHECK
   if test x"$has_64bit_asm" = x"yes"; then
@@ -488,10 +530,34 @@ if test x"$enable_module_ecdh" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_ECDH, 1, [Define this symbol to enable the ECDH module])
 fi
 
+if test x"$enable_module_schnorrsig" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_SCHNORRSIG, 1, [Define this symbol to enable the schnorrsig module])
+fi
+
+if test x"$enable_module_musig" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_MUSIG, 1, [Define this symbol to enable the MuSig module])
+fi
+
 if test x"$enable_module_recovery" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_RECOVERY, 1, [Define this symbol to enable the ECDSA pubkey recovery module])
 fi
 
+if test x"$enable_module_generator" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_GENERATOR, 1, [Define this symbol to enable the NUMS generator module])
+fi
+
+if test x"$enable_module_rangeproof" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_RANGEPROOF, 1, [Define this symbol to enable the Pedersen / zero knowledge range proof module])
+fi
+
+if test x"$enable_module_whitelist" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_WHITELIST, 1, [Define this symbol to enable the key whitelisting module])
+fi
+
+if test x"$enable_module_surjectionproof" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_SURJECTIONPROOF, 1, [Define this symbol to enable the surjection proof module])
+fi
+
 AC_C_BIGENDIAN()
 
 if test x"$use_external_asm" = x"yes"; then
@@ -507,14 +573,60 @@ if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([WARNING: experimental build])
   AC_MSG_NOTICE([Experimental features do not have stable APIs or properties, and may not be safe for production use.])
   AC_MSG_NOTICE([Building ECDH module: $enable_module_ecdh])
+  AC_MSG_NOTICE([Building NUMS generator module: $enable_module_generator])
+  AC_MSG_NOTICE([Building range proof module: $enable_module_rangeproof])
+  AC_MSG_NOTICE([Building key whitelisting module: $enable_module_whitelist])
+  AC_MSG_NOTICE([Building surjection proof module: $enable_module_surjectionproof])
+  AC_MSG_NOTICE([Building schnorrsig module: $enable_module_schnorrsig])
+  AC_MSG_NOTICE([Building MuSig module: $enable_module_musig])
   AC_MSG_NOTICE([******])
+
+
+  if test x"$enable_module_schnorrsig" != x"yes"; then
+    if test x"$enable_module_musig" = x"yes"; then
+      AC_MSG_ERROR([MuSig module requires the schnorrsig module. Use --enable-module-schnorrsig to allow.])
+    fi
+  fi
+
+  if test x"$enable_module_generator" != x"yes"; then
+    if test x"$enable_module_rangeproof" = x"yes"; then
+      AC_MSG_ERROR([Rangeproof module requires the generator module. Use --enable-module-generator to allow.])
+    fi
+  fi
+
+  if test x"$enable_module_rangeproof" != x"yes"; then
+    if test x"$enable_module_whitelist" = x"yes"; then
+      AC_MSG_ERROR([Whitelist module requires the rangeproof module. Use --enable-module-rangeproof to allow.])
+    fi
+    if test x"$enable_module_surjectionproof" = x"yes"; then
+      AC_MSG_ERROR([Surjection proof module requires the rangeproof module. Use --enable-module-rangeproof to allow.])
+    fi
+  fi
 else
   if test x"$enable_module_ecdh" = x"yes"; then
     AC_MSG_ERROR([ECDH module is experimental. Use --enable-experimental to allow.])
   fi
+  if test x"$enable_module_schnorrsig" = x"yes"; then
+    AC_MSG_ERROR([schnorrsig module is experimental. Use --enable-experimental to allow.])
+  fi
+  if test x"$enable_module_musig" = x"yes"; then
+    AC_MSG_ERROR([MuSig module is experimental. Use --enable-experimental to allow.])
+  fi
   if test x"$set_asm" = x"arm"; then
     AC_MSG_ERROR([ARM assembly optimization is experimental. Use --enable-experimental to allow.])
   fi
+  if test x"$enable_module_generator" = x"yes"; then
+    AC_MSG_ERROR([NUMS generator module is experimental. Use --enable-experimental to allow.])
+  fi
+  if test x"$enable_module_rangeproof" = x"yes"; then
+    AC_MSG_ERROR([Range proof module is experimental. Use --enable-experimental to allow.])
+  fi
+  if test x"$enable_module_whitelist" = x"yes"; then
+    AC_MSG_ERROR([Key whitelisting module is experimental. Use --enable-experimental to allow.])
+  fi
+  if test x"$enable_module_surjectionproof" = x"yes"; then
+    AC_MSG_ERROR([Surjection proof module is experimental. Use --enable-experimental to allow.])
+  fi
 fi
 
 AC_CONFIG_HEADERS([src/libsecp256k1-config.h])
@@ -530,10 +642,16 @@ AM_CONDITIONAL([USE_EXHAUSTIVE_TESTS], [test x"$use_exhaustive_tests" != x"no"])
 AM_CONDITIONAL([USE_BENCHMARK], [test x"$use_benchmark" = x"yes"])
 AM_CONDITIONAL([USE_ECMULT_STATIC_PRECOMPUTATION], [test x"$set_precomp" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_ECDH], [test x"$enable_module_ecdh" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_SCHNORRSIG], [test x"$enable_module_schnorrsig" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_MUSIG], [test x"$enable_module_musig" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_RECOVERY], [test x"$enable_module_recovery" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_GENERATOR], [test x"$enable_module_generator" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_RANGEPROOF], [test x"$enable_module_rangeproof" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_WHITELIST], [test x"$enable_module_whitelist" = x"yes"])
 AM_CONDITIONAL([USE_JNI], [test x"$use_jni" = x"yes"])
 AM_CONDITIONAL([USE_EXTERNAL_ASM], [test x"$use_external_asm" = x"yes"])
 AM_CONDITIONAL([USE_ASM_ARM], [test x"$set_asm" = x"arm"])
+AM_CONDITIONAL([ENABLE_MODULE_SURJECTIONPROOF], [test x"$enable_module_surjectionproof" = x"yes"])
 
 dnl make sure nothing new is exported so that we don't break the cache
 PKGCONFIG_PATH_TEMP="$PKG_CONFIG_PATH"

include/secp256k1_generator.h

@@ -0,0 +1,93 @@
+#ifndef _SECP256K1_GENERATOR_
+# define _SECP256K1_GENERATOR_
+
+# include "secp256k1.h"
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+#include <stdint.h>
+
+/** Opaque data structure that stores a base point
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
+ *  If you need to convert to a format suitable for storage, transmission, or
+ *  comparison, use secp256k1_generator_serialize and secp256k1_generator_parse.
+ */
+typedef struct {
+    unsigned char data[64];
+} secp256k1_generator;
+
+/** Parse a 33-byte generator byte sequence into a generator object.
+ *
+ *  Returns: 1 if input contains a valid generator.
+ *  Args: ctx:      a secp256k1 context object.
+ *  Out:  gen:      pointer to the output generator object
+ *  In:   input:    pointer to a 33-byte serialized generator
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_generator_parse(
+    const secp256k1_context* ctx,
+    secp256k1_generator* gen,
+    const unsigned char *input
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize a 33-byte generator into a serialized byte sequence.
+ *
+ *  Returns: 1 always.
+ *  Args:   ctx:        a secp256k1 context object.
+ *  Out:    output:     a pointer to a 33-byte byte array
+ *  In:     gen:        a pointer to a generator
+ */
+SECP256K1_API int secp256k1_generator_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *output,
+    const secp256k1_generator* gen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Generate a generator for the curve.
+ *
+ *  Returns: 0 in the highly unlikely case the seed is not acceptable,
+ *           1 otherwise.
+ *  Args: ctx:     a secp256k1 context object
+ *  Out:  gen:     a generator object
+ *  In:   seed32:  a 32-byte seed
+ *
+ *  If successful a valid generator will be placed in gen. The produced
+ *  generators are distributed uniformly over the curve, and will not have a
+ *  known discrete logarithm with respect to any other generator produced,
+ *  or to the base generator G.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_generator_generate(
+    const secp256k1_context* ctx,
+    secp256k1_generator* gen,
+    const unsigned char *seed32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Generate a blinded generator for the curve.
+ *
+ *  Returns: 0 in the highly unlikely case the seed is not acceptable or when
+ *           blind is out of range. 1 otherwise.
+ *  Args: ctx:     a secp256k1 context object, initialized for signing
+ *  Out:  gen:     a generator object
+ *  In:   seed32:  a 32-byte seed
+ *        blind32: a 32-byte secret value to blind the generator with.
+ *
+ *  The result is equivalent to first calling secp256k1_generator_generate,
+ *  converting the result to a public key, calling secp256k1_ec_pubkey_tweak_add,
+ *  and then converting back to generator form.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_generator_generate_blinded(
+    const secp256k1_context* ctx,
+    secp256k1_generator* gen,
+    const unsigned char *key32,
+    const unsigned char *blind32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+# ifdef __cplusplus
+}
+# endif
+
+#endif

include/secp256k1_musig.h

@@ -0,0 +1,422 @@
+#ifndef SECP256K1_MUSIG_H
+#define SECP256K1_MUSIG_H
+
+#include <stdint.h>
+
+/** This module implements a Schnorr-based multi-signature scheme called MuSig
+ * (https://eprint.iacr.org/2018/068.pdf). There's an example C source file in the
+ * module's directory (src/modules/musig/example.c) that demonstrates how it can be
+ * used.
+ *
+ * The documentation in this include file is for reference and may not be sufficient
+ * for users to begin using the library. A full description of API usage can be found
+ * in src/modules/musig/musig.md
+ */
+
+/** Data structure containing data related to a signing session resulting in a single
+ * signature.
+ *
+ * This structure is not opaque, but it MUST NOT be copied or read or written to it
+ * directly. A signer who is online throughout the whole process and can keep this
+ * structure in memory can use the provided API functions for a safe standard
+ * workflow. See https://blockstream.com/2019/02/18/musig-a-new-multisignature-standard/
+ * for more details about the risks associated with serializing or deserializing this
+ * structure.
+ *
+ * Fields:
+ *      combined_pk: MuSig-computed combined public key
+ *        n_signers: Number of signers
+ *          pk_hash: The 32-byte hash of the original public keys
+ *   combined_nonce: Summed combined public nonce (undefined if `nonce_is_set` is false)
+ *     nonce_is_set: Whether the above nonce has been set
+ * nonce_is_negated: If `nonce_is_set`, whether the above nonce was negated after
+ *                   summing the participants' nonces. Needed to ensure the nonce's y
+ *                   coordinate has a quadratic-residue y coordinate
+ *              msg: The 32-byte message (hash) to be signed
+ *       msg_is_set: Whether the above message has been set
+ *  has_secret_data: Whether this session object has a signers' secret data; if this
+ *                   is `false`, it may still be used for verification purposes.
+ *           seckey: If `has_secret_data`, the signer's secret key
+ *         secnonce: If `has_secret_data`, the signer's secret nonce
+ *            nonce: If `has_secret_data`, the signer's public nonce
+ * nonce_commitments_hash: If `has_secret_data` and `nonce_commitments_hash_is_set`,
+ *                   the hash of all signers' commitments
+ * nonce_commitments_hash_is_set: If `has_secret_data`, whether the
+ *                   nonce_commitments_hash has been set
+ */
+typedef struct {
+    secp256k1_pubkey combined_pk;
+    uint32_t n_signers;
+    unsigned char pk_hash[32];
+    secp256k1_pubkey combined_nonce;
+    int nonce_is_set;
+    int nonce_is_negated;
+    unsigned char msg[32];
+    int msg_is_set;
+    int has_secret_data;
+    unsigned char seckey[32];
+    unsigned char secnonce[32];
+    secp256k1_pubkey nonce;
+    unsigned char nonce_commitments_hash[32];
+    int nonce_commitments_hash_is_set;
+} secp256k1_musig_session;
+
+/** Data structure containing data on all signers in a single session.
+ *
+ * The workflow for this structure is as follows:
+ *
+ * 1. This structure is initialized with `musig_session_initialize` or
+ *    `musig_session_initialize_verifier`, which set the `index` field, and zero out
+ *    all other fields. The public session is initialized with the signers'
+ *    nonce_commitments.
+ *
+ * 2. In a non-public session the nonce_commitments are set with the function
+ *    `musig_get_public_nonce`, which also returns the signer's public nonce. This
+ *    ensures that the public nonce is not exposed until all commitments have been
+ *    received.
+ *
+ * 3. Each individual data struct should be updated with `musig_set_nonce` once a
+ *    nonce is available. This function takes a single signer data struct rather than
+ *    an array because it may fail in the case that the provided nonce does not match
+ *    the commitment. In this case, it is desirable to identify the exact party whose
+ *    nonce was inconsistent.
+ *
+ * Fields:
+ *   present: indicates whether the signer's nonce is set
+ *     index: index of the signer in the MuSig key aggregation
+ *     nonce: public nonce, must be a valid curvepoint if the signer is `present`
+ * nonce_commitment: commitment to the nonce, or all-bits zero if a commitment
+ *                   has not yet been set
+ */
+typedef struct {
+    int present;
+    uint32_t index;
+    secp256k1_pubkey nonce;
+    unsigned char nonce_commitment[32];
+} secp256k1_musig_session_signer_data;
+
+/** Opaque data structure that holds a MuSig partial signature.
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is however
+ *  guaranteed to be 32 bytes in size, and can be safely copied/moved. If you need
+ *  to convert to a format suitable for storage, transmission, or comparison, use the
+ *  `musig_partial_signature_serialize` and `musig_partial_signature_parse`
+ *  functions.
+ */
+typedef struct {
+    unsigned char data[32];
+} secp256k1_musig_partial_signature;
+
+/** Computes a combined public key and the hash of the given public keys
+ *
+ *  Returns: 1 if the public keys were successfully combined, 0 otherwise
+ *  Args:        ctx: pointer to a context object initialized for verification
+ *                    (cannot be NULL)
+ *           scratch: scratch space used to compute the combined pubkey by
+ *                    multiexponentiation. If NULL, an inefficient algorithm is used.
+ *  Out: combined_pk: the MuSig-combined public key (cannot be NULL)
+ *         pk_hash32: if non-NULL, filled with the 32-byte hash of all input public
+ *                    keys in order to be used in `musig_session_initialize`.
+ *   In:     pubkeys: input array of public keys to combine. The order is important;
+ *                    a different order will result in a different combined public
+ *                    key (cannot be NULL)
+ *         n_pubkeys: length of pubkeys array
+ */
+SECP256K1_API int secp256k1_musig_pubkey_combine(
+    const secp256k1_context* ctx,
+    secp256k1_scratch_space *scratch,
+    secp256k1_pubkey *combined_pk,
+    unsigned char *pk_hash32,
+    const secp256k1_pubkey *pubkeys,
+    size_t n_pubkeys
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
+
+/** Initializes a signing session for a signer
+ *
+ *  Returns: 1: session is successfully initialized
+ *           0: session could not be initialized: secret key or secret nonce overflow
+ *  Args:         ctx: pointer to a context object, initialized for signing (cannot
+ *                     be NULL)
+ *  Out:      session: the session structure to initialize (cannot be NULL)
+ *            signers: an array of signers' data to be initialized. Array length must
+ *                     equal to `n_signers` (cannot be NULL)
+ * nonce_commitment32: filled with a 32-byte commitment to the generated nonce
+ *                     (cannot be NULL)
+ *  In:  session_id32: a *unique* 32-byte ID to assign to this session (cannot be
+ *                     NULL). If a non-unique session_id32 was given then a partial
+ *                     signature will LEAK THE SECRET KEY.
+ *              msg32: the 32-byte message to be signed. Shouldn't be NULL unless you
+ *                     require sharing public nonces before the message is known
+ *                     because it reduces nonce misuse resistance. If NULL, must be
+ *                     set with `musig_session_set_msg` before signing and verifying.
+ *        combined_pk: the combined public key of all signers (cannot be NULL)
+ *          pk_hash32: the 32-byte hash of the signers' individual keys (cannot be
+ *                     NULL)
+ *          n_signers: length of signers array. Number of signers participating in
+ *                     the MuSig. Must be greater than 0 and at most 2^32 - 1.
+ *           my_index: index of this signer in the signers array
+ *             seckey: the signer's 32-byte secret key (cannot be NULL)
+ */
+SECP256K1_API int secp256k1_musig_session_initialize(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session *session,
+    secp256k1_musig_session_signer_data *signers,
+    unsigned char *nonce_commitment32,
+    const unsigned char *session_id32,
+    const unsigned char *msg32,
+    const secp256k1_pubkey *combined_pk,
+    const unsigned char *pk_hash32,
+    size_t n_signers,
+    size_t my_index,
+    const unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8) SECP256K1_ARG_NONNULL(11);
+
+/** Gets the signer's public nonce given a list of all signers' data with commitments
+ *
+ *  Returns: 1: public nonce is written in nonce
+ *           0: signer data is missing commitments or session isn't initialized
+ *              for signing
+ *  Args:        ctx: pointer to a context object (cannot be NULL)
+ *           session: the signing session to get the nonce from (cannot be NULL)
+ *           signers: an array of signers' data initialized with
+ *                    `musig_session_initialize`. Array length must equal to
+ *                    `n_commitments` (cannot be NULL)
+ *  Out:       nonce: the nonce (cannot be NULL)
+ *  In:  commitments: array of 32-byte nonce commitments (cannot be NULL)
+ *     n_commitments: the length of commitments and signers array. Must be the total
+ *                    number of signers participating in the MuSig.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_session_get_public_nonce(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session *session,
+    secp256k1_musig_session_signer_data *signers,
+    secp256k1_pubkey *nonce,
+    const unsigned char *const *commitments,
+    size_t n_commitments
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+/** Initializes a verifier session that can be used for verifying nonce commitments
+ *  and partial signatures. It does not have secret key material and therefore can not
+ *  be used to create signatures.
+ *
+ *  Returns: 1 when session is successfully initialized, 0 otherwise
+ *  Args:        ctx: pointer to a context object (cannot be NULL)
+ *  Out:     session: the session structure to initialize (cannot be NULL)
+ *           signers: an array of signers' data to be initialized. Array length must
+ *                    equal to `n_signers`(cannot be NULL)
+ *  In:        msg32: the 32-byte message to be signed If NULL, must be set with
+ *                    `musig_session_set_msg` before using the session for verifying
+ *                    partial signatures.
+ *       combined_pk: the combined public key of all signers (cannot be NULL)
+ *         pk_hash32: the 32-byte hash of the signers' individual keys (cannot be NULL)
+ *       commitments: array of 32-byte nonce commitments. Array length must equal to
+ *                    `n_signers` (cannot be NULL)
+ *         n_signers: length of signers and commitments array. Number of signers
+ *                    participating in the MuSig. Must be greater than 0 and at most
+ *                    2^32 - 1.
+ */
+SECP256K1_API int secp256k1_musig_session_initialize_verifier(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session *session,
+    secp256k1_musig_session_signer_data *signers,
+    const unsigned char *msg32,
+    const secp256k1_pubkey *combined_pk,
+    const unsigned char *pk_hash32,
+    const unsigned char *const *commitments,
+    size_t n_signers
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7);
+
+/** Checks a signer's public nonce against a commitment to said nonce, and update
+ *  data structure if they match
+ *
+ *  Returns: 1: commitment was valid, data structure updated
+ *           0: commitment was invalid, nothing happened
+ *  Args:      ctx: pointer to a context object (cannot be NULL)
+ *          signer: pointer to the signer data to update (cannot be NULL). Must have
+ *                  been used with `musig_session_get_public_nonce` or initialized
+ *                  with `musig_session_initialize_verifier`.
+ *  In:     nonce: signer's alleged public nonce (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_set_nonce(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session_signer_data *signer,
+    const secp256k1_pubkey *nonce
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Updates a session with the combined public nonce of all signers. The combined
+ * public nonce is the sum of every signer's public nonce.
+ *
+ *  Returns: 1: nonces are successfully combined
+ *           0: a signer's nonce is missing
+ *  Args:        ctx: pointer to a context object (cannot be NULL)
+ *           session: session to update with the combined public nonce (cannot be
+ *                    NULL)
+ *           signers: an array of signers' data, which must have had public nonces
+ *                    set with `musig_set_nonce`. Array length must equal to `n_signers`
+ *                    (cannot be NULL)
+ *         n_signers: the length of the signers array. Must be the total number of
+ *                    signers participating in the MuSig.
+ *  Out: nonce_is_negated: a pointer to an integer that indicates if the combined
+ *                    public nonce had to be negated.
+ *           adaptor: point to add to the combined public nonce. If NULL, nothing is
+ *                    added to the combined nonce.
+ */
+SECP256K1_API int secp256k1_musig_session_combine_nonces(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session *session,
+    const secp256k1_musig_session_signer_data *signers,
+    size_t n_signers,
+    int *nonce_is_negated,
+    const secp256k1_pubkey *adaptor
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+/** Sets the message of a session if previously unset
+ *
+ *  Returns 1 if the message was not set yet and is now successfully set
+ *          0 otherwise
+ *  Args:    ctx: pointer to a context object (cannot be NULL)
+ *       session: the session structure to update with the message (cannot be NULL)
+ *  In:    msg32: the 32-byte message to be signed (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_session_set_msg(
+    const secp256k1_context* ctx,
+    secp256k1_musig_session *session,
+    const unsigned char *msg32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize a MuSig partial signature or adaptor signature
+ *
+ *  Returns: 1 when the signature could be serialized, 0 otherwise
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:   out32: pointer to a 32-byte array to store the serialized signature
+ *  In:      sig: pointer to the signature
+ */
+SECP256K1_API int secp256k1_musig_partial_signature_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *out32,
+    const secp256k1_musig_partial_signature* sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Parse and verify a MuSig partial signature.
+ *
+ *  Returns: 1 when the signature could be parsed, 0 otherwise.
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:     sig: pointer to a signature object
+ *  In:     in32: pointer to the 32-byte signature to be parsed
+ *
+ *  After the call, sig will always be initialized. If parsing failed or the
+ *  encoded numbers are out of range, signature verification with it is
+ *  guaranteed to fail for every message and public key.
+ */
+SECP256K1_API int secp256k1_musig_partial_signature_parse(
+    const secp256k1_context* ctx,
+    secp256k1_musig_partial_signature* sig,
+    const unsigned char *in32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Produces a partial signature
+ *
+ *  Returns: 1: partial signature constructed
+ *           0: session in incorrect or inconsistent state
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *            session: active signing session for which the combined nonce has been
+ *                     computed (cannot be NULL)
+ *  Out:  partial_sig: partial signature (cannot be NULL)
+ */
+SECP256K1_API int secp256k1_musig_partial_sign(
+    const secp256k1_context* ctx,
+    const secp256k1_musig_session *session,
+    secp256k1_musig_partial_signature *partial_sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Checks that an individual partial signature verifies
+ *
+ *  This function is essential when using protocols with adaptor signatures.
+ *  However, it is not essential for regular MuSig's, in the sense that if any
+ *  partial signatures does not verify, the full signature will also not verify, so the
+ *  problem will be caught. But this function allows determining the specific party
+ *  who produced an invalid signature, so that signing can be restarted without them.
+ *
+ *  Returns: 1: partial signature verifies
+ *           0: invalid signature or bad data
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *            session: active session for which the combined nonce has been computed
+ *                     (cannot be NULL)
+ *             signer: data for the signer who produced this signature (cannot be NULL)
+ *  In:   partial_sig: signature to verify (cannot be NULL)
+ *             pubkey: public key of the signer who produced the signature (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_partial_sig_verify(
+    const secp256k1_context* ctx,
+    const secp256k1_musig_session *session,
+    const secp256k1_musig_session_signer_data *signer,
+    const secp256k1_musig_partial_signature *partial_sig,
+    const secp256k1_pubkey *pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+/** Combines partial signatures
+ *
+ *  Returns: 1: all partial signatures have values in range. Does NOT mean the
+ *              resulting signature verifies.
+ *           0: some partial signature had s/r out of range
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *            session: initialized session for which the combined nonce has been
+ *                     computed (cannot be NULL)
+ *  Out:          sig: complete signature (cannot be NULL)
+ *  In:  partial_sigs: array of partial signatures to combine (cannot be NULL)
+ *             n_sigs: number of signatures in the partial_sigs array
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_partial_sig_combine(
+    const secp256k1_context* ctx,
+    const secp256k1_musig_session *session,
+    secp256k1_schnorrsig *sig,
+    const secp256k1_musig_partial_signature *partial_sigs,
+    size_t n_sigs
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Converts a partial signature to an adaptor signature by adding a given secret
+ *  adaptor.
+ *
+ *  Returns: 1: signature and secret adaptor contained valid values
+ *           0: otherwise
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *  Out:  adaptor_sig: adaptor signature to produce (cannot be NULL)
+ *  In:   partial_sig: partial signature to tweak with secret adaptor (cannot be NULL)
+ *      sec_adaptor32: 32-byte secret adaptor to add to the partial signature (cannot
+ *                     be NULL)
+ *   nonce_is_negated: the `nonce_is_negated` output of `musig_session_combine_nonces`
+ */
+SECP256K1_API int secp256k1_musig_partial_sig_adapt(
+    const secp256k1_context* ctx,
+    secp256k1_musig_partial_signature *adaptor_sig,
+    const secp256k1_musig_partial_signature *partial_sig,
+    const unsigned char *sec_adaptor32,
+    int nonce_is_negated
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Extracts a secret adaptor from a MuSig, given all parties' partial
+ *  signatures. This function will not fail unless given grossly invalid data; if it
+ *  is merely given signatures that do not verify, the returned value will be
+ *  nonsense. It is therefore important that all data be verified at earlier steps of
+ *  any protocol that uses this function.
+ *
+ *  Returns: 1: signatures contained valid data such that an adaptor could be extracted
+ *           0: otherwise
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *  Out:sec_adaptor32: 32-byte secret adaptor (cannot be NULL)
+ *  In:           sig: complete 2-of-2 signature (cannot be NULL)
+ *       partial_sigs: array of partial signatures (cannot be NULL)
+ *     n_partial_sigs: number of elements in partial_sigs array
+ *   nonce_is_negated: the `nonce_is_negated` output of `musig_session_combine_nonces`
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_extract_secret_adaptor(
+    const secp256k1_context* ctx,
+    unsigned char *sec_adaptor32,
+    const secp256k1_schnorrsig *sig,
+    const secp256k1_musig_partial_signature *partial_sigs,
+    size_t n_partial_sigs,
+    int nonce_is_negated
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+#endif

include/secp256k1_rangeproof.h

@@ -0,0 +1,297 @@
+#ifndef _SECP256K1_RANGEPROOF_
+# define _SECP256K1_RANGEPROOF_
+
+# include "secp256k1.h"
+# include "secp256k1_generator.h"
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+#include <stdint.h>
+
+/** Opaque data structure that stores a Pedersen commitment
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
+ *  If you need to convert to a format suitable for storage, transmission, or
+ *  comparison, use secp256k1_pedersen_commitment_serialize and
+ *  secp256k1_pedersen_commitment_parse.
+ */
+typedef struct {
+    unsigned char data[64];
+} secp256k1_pedersen_commitment;
+
+/**
+ * Static constant generator 'h' maintained for historical reasons.
+ */
+SECP256K1_API extern const secp256k1_generator *secp256k1_generator_h;
+
+/** Parse a 33-byte commitment into a commitment object.
+ *
+ *  Returns: 1 if input contains a valid commitment.
+ *  Args: ctx:      a secp256k1 context object.
+ *  Out:  commit:   pointer to the output commitment object
+ *  In:   input:    pointer to a 33-byte serialized commitment key
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_commitment_parse(
+    const secp256k1_context* ctx,
+    secp256k1_pedersen_commitment* commit,
+    const unsigned char *input
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize a commitment object into a serialized byte sequence.
+ *
+ *  Returns: 1 always.
+ *  Args:   ctx:        a secp256k1 context object.
+ *  Out:    output:     a pointer to a 33-byte byte array
+ *  In:     commit:     a pointer to a secp256k1_pedersen_commitment containing an
+ *                      initialized commitment
+ */
+SECP256K1_API int secp256k1_pedersen_commitment_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *output,
+    const secp256k1_pedersen_commitment* commit
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Initialize a context for usage with Pedersen commitments. */
+void secp256k1_pedersen_context_initialize(secp256k1_context* ctx);
+
+/** Generate a pedersen commitment.
+ *  Returns 1: Commitment successfully created.
+ *          0: Error. The blinding factor is larger than the group order
+ *             (probability for random 32 byte number < 2^-127) or results in the
+ *             point at infinity. Retry with a different factor.
+ *  In:     ctx:        pointer to a context object, initialized for signing and Pedersen commitment (cannot be NULL)
+ *          blind:      pointer to a 32-byte blinding factor (cannot be NULL)
+ *          value:      unsigned 64-bit integer value to commit to.
+ *          gen:        additional generator 'h'
+ *  Out:    commit:     pointer to the commitment (cannot be NULL)
+ *
+ *  Blinding factors can be generated and verified in the same way as secp256k1 private keys for ECDSA.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_commit(
+  const secp256k1_context* ctx,
+  secp256k1_pedersen_commitment *commit,
+  const unsigned char *blind,
+  uint64_t value,
+  const secp256k1_generator *gen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
+
+/** Computes the sum of multiple positive and negative blinding factors.
+ *  Returns 1: Sum successfully computed.
+ *          0: Error. A blinding factor is larger than the group order
+ *             (probability for random 32 byte number < 2^-127). Retry with
+ *             different factors.
+ *  In:     ctx:        pointer to a context object (cannot be NULL)
+ *          blinds:     pointer to pointers to 32-byte character arrays for blinding factors. (cannot be NULL)
+ *          n:          number of factors pointed to by blinds.
+ *          npositive:       how many of the initial factors should be treated with a positive sign.
+ *  Out:    blind_out:  pointer to a 32-byte array for the sum (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_blind_sum(
+  const secp256k1_context* ctx,
+  unsigned char *blind_out,
+  const unsigned char * const *blinds,
+  size_t n,
+  size_t npositive
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Verify a tally of pedersen commitments
+ * Returns 1: commitments successfully sum to zero.
+ *         0: Commitments do not sum to zero or other error.
+ * In:     ctx:        pointer to a context object (cannot be NULL)
+ *         commits:    pointer to array of pointers to the commitments. (cannot be NULL if pcnt is non-zero)
+ *         pcnt:       number of commitments pointed to by commits.
+ *         ncommits:   pointer to array of pointers to the negative commitments. (cannot be NULL if ncnt is non-zero)
+ *         ncnt:       number of commitments pointed to by ncommits.
+ *
+ * This computes sum(commit[0..pcnt)) - sum(ncommit[0..ncnt)) == 0.
+ *
+ * A pedersen commitment is xG + vA where G and A are generators for the secp256k1 group and x is a blinding factor,
+ * while v is the committed value. For a collection of commitments to sum to zero, for each distinct generator
+ * A all blinding factors and all values must sum to zero.
+ *
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_verify_tally(
+  const secp256k1_context* ctx,
+  const secp256k1_pedersen_commitment * const* commits,
+  size_t pcnt,
+  const secp256k1_pedersen_commitment * const* ncommits,
+  size_t ncnt
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+/** Sets the final Pedersen blinding factor correctly when the generators themselves
+ *  have blinding factors.
+ *
+ * Consider a generator of the form A' = A + rG, where A is the "real" generator
+ * but A' is the generator provided to verifiers. Then a Pedersen commitment
+ * P = vA' + r'G really has the form vA + (vr + r')G. To get all these (vr + r')
+ * to sum to zero for multiple commitments, we take three arrays consisting of
+ * the `v`s, `r`s, and `r'`s, respectively called `value`s, `generator_blind`s
+ * and `blinding_factor`s, and sum them.
+ *
+ * The function then subtracts the sum of all (vr + r') from the last element
+ * of the `blinding_factor` array, setting the total sum to zero.
+ *
+ * Returns 1: Blinding factor successfully computed.
+ *         0: Error. A blinding_factor or generator_blind are larger than the group
+ *            order (probability for random 32 byte number < 2^-127). Retry with
+ *            different values.
+ *
+ * In:                 ctx: pointer to a context object
+ *                   value: array of asset values, `v` in the above paragraph.
+ *                          May not be NULL unless `n_total` is 0.
+ *         generator_blind: array of asset blinding factors, `r` in the above paragraph
+ *                          May not be NULL unless `n_total` is 0.
+ *                 n_total: Total size of the above arrays
+ *                n_inputs: How many of the initial array elements represent commitments that
+ *                          will be negated in the final sum
+ * In/Out: blinding_factor: array of commitment blinding factors, `r'` in the above paragraph
+ *                          May not be NULL unless `n_total` is 0.
+ *                          the last value will be modified to get the total sum to zero.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_blind_generator_blind_sum(
+  const secp256k1_context* ctx,
+  const uint64_t *value,
+  const unsigned char* const* generator_blind,
+  unsigned char* const* blinding_factor,
+  size_t n_total,
+  size_t n_inputs
+);
+
+/** Initialize a context for usage with Pedersen commitments. */
+void secp256k1_rangeproof_context_initialize(secp256k1_context* ctx);
+
+/** Verify a proof that a committed value is within a range.
+ * Returns 1: Value is within the range [0..2^64), the specifically proven range is in the min/max value outputs.
+ *         0: Proof failed or other error.
+ * In:   ctx: pointer to a context object, initialized for range-proof and commitment (cannot be NULL)
+ *       commit: the commitment being proved. (cannot be NULL)
+ *       proof: pointer to character array with the proof. (cannot be NULL)
+ *       plen: length of proof in bytes.
+ *       extra_commit: additional data covered in rangeproof signature
+ *       extra_commit_len: length of extra_commit byte array (0 if NULL)
+ *       gen: additional generator 'h'
+ * Out:  min_value: pointer to a unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
+ *       max_value: pointer to a unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_verify(
+  const secp256k1_context* ctx,
+  uint64_t *min_value,
+  uint64_t *max_value,
+  const secp256k1_pedersen_commitment *commit,
+  const unsigned char *proof,
+  size_t plen,
+  const unsigned char *extra_commit,
+  size_t extra_commit_len,
+  const secp256k1_generator* gen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(9);
+
+/** Verify a range proof proof and rewind the proof to recover information sent by its author.
+ *  Returns 1: Value is within the range [0..2^64), the specifically proven range is in the min/max value outputs, and the value and blinding were recovered.
+ *          0: Proof failed, rewind failed, or other error.
+ *  In:   ctx: pointer to a context object, initialized for range-proof and Pedersen commitment (cannot be NULL)
+ *        commit: the commitment being proved. (cannot be NULL)
+ *        proof: pointer to character array with the proof. (cannot be NULL)
+ *        plen: length of proof in bytes.
+ *        nonce: 32-byte secret nonce used by the prover (cannot be NULL)
+ *        extra_commit: additional data covered in rangeproof signature
+ *        extra_commit_len: length of extra_commit byte array (0 if NULL)
+ *        gen: additional generator 'h'
+ *  In/Out: blind_out: storage for the 32-byte blinding factor used for the commitment
+ *        value_out: pointer to an unsigned int64 which has the exact value of the commitment.
+ *        message_out: pointer to a 4096 byte character array to receive message data from the proof author.
+ *        outlen:  length of message data written to message_out.
+ *        min_value: pointer to an unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
+ *        max_value: pointer to an unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_rewind(
+  const secp256k1_context* ctx,
+  unsigned char *blind_out,
+  uint64_t *value_out,
+  unsigned char *message_out,
+  size_t *outlen,
+  const unsigned char *nonce,
+  uint64_t *min_value,
+  uint64_t *max_value,
+  const secp256k1_pedersen_commitment *commit,
+  const unsigned char *proof,
+  size_t plen,
+  const unsigned char *extra_commit,
+  size_t extra_commit_len,
+  const secp256k1_generator *gen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8) SECP256K1_ARG_NONNULL(9) SECP256K1_ARG_NONNULL(10) SECP256K1_ARG_NONNULL(14);
+
+/** Author a proof that a committed value is within a range.
+ *  Returns 1: Proof successfully created.
+ *          0: Error
+ *  In:     ctx:    pointer to a context object, initialized for range-proof, signing, and Pedersen commitment (cannot be NULL)
+ *          proof:  pointer to array to receive the proof, can be up to 5134 bytes. (cannot be NULL)
+ *          min_value: constructs a proof where the verifer can tell the minimum value is at least the specified amount.
+ *          commit: the commitment being proved.
+ *          blind:  32-byte blinding factor used by commit.
+ *          nonce:  32-byte secret nonce used to initialize the proof (value can be reverse-engineered out of the proof if this secret is known.)
+ *          exp:    Base-10 exponent. Digits below above will be made public, but the proof will be made smaller. Allowed range is -1 to 18.
+ *                  (-1 is a special case that makes the value public. 0 is the most private.)
+ *          min_bits: Number of bits of the value to keep private. (0 = auto/minimal, - 64).
+ *          value:  Actual value of the commitment.
+ *          message: pointer to a byte array of data to be embedded in the rangeproof that can be recovered by rewinding the proof
+ *          msg_len: size of the message to be embedded in the rangeproof
+ *          extra_commit: additional data to be covered in rangeproof signature
+ *          extra_commit_len: length of extra_commit byte array (0 if NULL)
+ *          gen: additional generator 'h'
+ *  In/out: plen:   point to an integer with the size of the proof buffer and the size of the constructed proof.
+ *
+ *  If min_value or exp is non-zero then the value must be on the range [0, 2^63) to prevent the proof range from spanning past 2^64.
+ *
+ *  If exp is -1 the value is revealed by the proof (e.g. it proves that the proof is a blinding of a specific value, without revealing the blinding key.)
+ *
+ *  This can randomly fail with probability around one in 2^100. If this happens, buy a lottery ticket and retry with a different nonce or blinding.
+ *
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_sign(
+  const secp256k1_context* ctx,
+  unsigned char *proof,
+  size_t *plen,
+  uint64_t min_value,
+  const secp256k1_pedersen_commitment *commit,
+  const unsigned char *blind,
+  const unsigned char *nonce,
+  int exp,
+  int min_bits,
+  uint64_t value,
+  const unsigned char *message,
+  size_t msg_len,
+  const unsigned char *extra_commit,
+  size_t extra_commit_len,
+  const secp256k1_generator *gen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(15);
+
+/** Extract some basic information from a range-proof.
+ *  Returns 1: Information successfully extracted.
+ *          0: Decode failed.
+ *  In:   ctx: pointer to a context object
+ *        proof: pointer to character array with the proof.
+ *        plen: length of proof in bytes.
+ *  Out:  exp: Exponent used in the proof (-1 means the value isn't private).
+ *        mantissa: Number of bits covered by the proof.
+ *        min_value: pointer to an unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
+ *        max_value: pointer to an unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_info(
+  const secp256k1_context* ctx,
+  int *exp,
+  int *mantissa,
+  uint64_t *min_value,
+  uint64_t *max_value,
+  const unsigned char *proof,
+  size_t plen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+# ifdef __cplusplus
+}
+# endif
+
+#endif

include/secp256k1_schnorrsig.h

@@ -0,0 +1,118 @@
+#ifndef SECP256K1_SCHNORRSIG_H
+#define SECP256K1_SCHNORRSIG_H
+
+/** This module implements a variant of Schnorr signatures compliant with
+ * BIP-schnorr
+ * (https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki).
+ */
+
+/** Opaque data structure that holds a parsed Schnorr signature.
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
+ *  If you need to convert to a format suitable for storage, transmission, or
+ *  comparison, use the `secp256k1_schnorrsig_serialize` and
+ *  `secp256k1_schnorrsig_parse` functions.
+ */
+typedef struct {
+    unsigned char data[64];
+} secp256k1_schnorrsig;
+
+/** Serialize a Schnorr signature.
+ *
+ *  Returns: 1
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:   out64: pointer to a 64-byte array to store the serialized signature
+ *  In:      sig: pointer to the signature
+ *
+ *  See secp256k1_schnorrsig_parse for details about the encoding.
+ */
+SECP256K1_API int secp256k1_schnorrsig_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *out64,
+    const secp256k1_schnorrsig* sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Parse a Schnorr signature.
+ *
+ *  Returns: 1 when the signature could be parsed, 0 otherwise.
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:     sig: pointer to a signature object
+ *  In:     in64: pointer to the 64-byte signature to be parsed
+ *
+ * The signature is serialized in the form R||s, where R is a 32-byte public
+ * key (x-coordinate only; the y-coordinate is considered to be the unique
+ * y-coordinate satisfying the curve equation that is a quadratic residue)
+ * and s is a 32-byte big-endian scalar.
+ *
+ * After the call, sig will always be initialized. If parsing failed or the
+ * encoded numbers are out of range, signature validation with it is
+ * guaranteed to fail for every message and public key.
+ */
+SECP256K1_API int secp256k1_schnorrsig_parse(
+    const secp256k1_context* ctx,
+    secp256k1_schnorrsig* sig,
+    const unsigned char *in64
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Create a Schnorr signature.
+ *
+ * Returns 1 on success, 0 on failure.
+ *  Args:    ctx: pointer to a context object, initialized for signing (cannot be NULL)
+ *  Out:     sig: pointer to the returned signature (cannot be NULL)
+ *       nonce_is_negated: a pointer to an integer indicates if signing algorithm negated the
+ *                nonce (can be NULL)
+ *  In:    msg32: the 32-byte message hash being signed (cannot be NULL)
+ *        seckey: pointer to a 32-byte secret key (cannot be NULL)
+ *       noncefp: pointer to a nonce generation function. If NULL, secp256k1_nonce_function_bipschnorr is used
+ *         ndata: pointer to arbitrary data used by the nonce generation function (can be NULL)
+ */
+SECP256K1_API int secp256k1_schnorrsig_sign(
+    const secp256k1_context* ctx,
+    secp256k1_schnorrsig *sig,
+    int *nonce_is_negated,
+    const unsigned char *msg32,
+    const unsigned char *seckey,
+    secp256k1_nonce_function noncefp,
+    void *ndata
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+/** Verify a Schnorr signature.
+ *
+ *  Returns: 1: correct signature
+ *           0: incorrect or unparseable signature
+ *  Args:    ctx: a secp256k1 context object, initialized for verification.
+ *  In:      sig: the signature being verified (cannot be NULL)
+ *         msg32: the 32-byte message hash being verified (cannot be NULL)
+ *        pubkey: pointer to a public key to verify with (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorrsig_verify(
+    const secp256k1_context* ctx,
+    const secp256k1_schnorrsig *sig,
+    const unsigned char *msg32,
+    const secp256k1_pubkey *pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Verifies a set of Schnorr signatures.
+ *
+ * Returns 1 if all succeeded, 0 otherwise. In particular, returns 1 if n_sigs is 0.
+ *
+ *  Args:    ctx: a secp256k1 context object, initialized for verification.
+ *       scratch: scratch space used for the multiexponentiation
+ *  In:      sig: array of signatures, or NULL if there are no signatures
+ *         msg32: array of messages, or NULL if there are no signatures
+ *            pk: array of public keys, or NULL if there are no signatures
+ *        n_sigs: number of signatures in above arrays. Must be smaller than
+ *                2^31 and smaller than half the maximum size_t value. Must be 0
+ *                if above arrays are NULL.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorrsig_verify_batch(
+    const secp256k1_context* ctx,
+    secp256k1_scratch_space *scratch,
+    const secp256k1_schnorrsig *const *sig,
+    const unsigned char *const *msg32,
+    const secp256k1_pubkey *const *pk,
+    size_t n_sigs
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+#endif

include/secp256k1_surjectionproof.h

@@ -0,0 +1,262 @@
+#ifndef _SECP256K1_SURJECTIONPROOF_
+#define _SECP256K1_SURJECTIONPROOF_
+
+#include "secp256k1.h"
+#include "secp256k1_rangeproof.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Maximum number of inputs that may be given in a surjection proof */
+#define SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS 256
+
+/** Number of bytes a serialized surjection proof requires given the
+ *  number of inputs and the number of used inputs.
+ */
+#define SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES(n_inputs, n_used_inputs) \
+    (2 + (n_inputs + 7)/8 + 32 * (1 + (n_used_inputs)))
+
+/** Maximum number of bytes a serialized surjection proof requires. */
+#define SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX \
+    SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS)
+
+/** Opaque data structure that holds a parsed surjection proof
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. Nor is
+ *  it guaranteed to have any particular size, nor that identical proofs
+ *  will have identical representation. (That is, memcmp may return nonzero
+ *  even for identical proofs.)
+ *
+ *  To obtain these properties, instead use secp256k1_surjectionproof_parse
+ *  and secp256k1_surjectionproof_serialize to encode/decode proofs into a
+ *  well-defined format.
+ *
+ *  The representation is exposed to allow creation of these objects on the
+ *  stack; please *do not* use these internals directly.
+ */
+typedef struct {
+#ifdef VERIFY
+    /** Mark whether this proof has gone through `secp256k1_surjectionproof_initialize` */
+    int initialized;
+#endif
+    /** Total number of input asset tags */
+    size_t n_inputs;
+    /** Bitmap of which input tags are used in the surjection proof */
+    unsigned char used_inputs[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS / 8];
+    /** Borromean signature: e0, scalars */
+    unsigned char data[32 * (1 + SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS)];
+} secp256k1_surjectionproof;
+
+/** Parse a surjection proof
+ *
+ *  Returns: 1 when the proof could be parsed, 0 otherwise.
+ *  Args: ctx:    a secp256k1 context object
+ *  Out:  proof:  a pointer to a proof object
+ *  In:   input:  a pointer to the array to parse
+ *        inputlen: length of the array pointed to by input
+ *
+ *  The proof must consist of:
+ *    - A 2-byte little-endian total input count `n`
+ *    - A ceil(n/8)-byte bitmap indicating which inputs are used.
+ *    - A big-endian 32-byte borromean signature e0 value
+ *    - `m` big-endian 32-byte borromean signature s values, where `m`
+ *      is the number of set bits in the bitmap
+ */
+SECP256K1_API int secp256k1_surjectionproof_parse(
+  const secp256k1_context* ctx,
+  secp256k1_surjectionproof *proof,
+  const unsigned char *input,
+  size_t inputlen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize a surjection proof
+ *
+ *  Returns: 1 if enough space was available to serialize, 0 otherwise
+ *  Args:   ctx:        a secp256k1 context object
+ *  Out:    output:     a pointer to an array to store the serialization
+ *  In/Out: outputlen:  a pointer to an integer which is initially set to the
+ *                      size of output, and is overwritten with the written
+ *                      size.
+ *  In:     proof:      a pointer to an initialized proof object
+ *
+ *  See secp256k1_surjectionproof_parse for details about the encoding.
+ */
+SECP256K1_API int secp256k1_surjectionproof_serialize(
+  const secp256k1_context* ctx,
+  unsigned char *output,
+  size_t *outputlen,
+  const secp256k1_surjectionproof *proof
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Data structure that holds a fixed asset tag.
+ *
+ * This data type is *not* opaque. It will always be 32 bytes of whatever
+ * data the API user wants to use as an asset tag. Its contents have no
+ * semantic meaning to libsecp whatsoever.
+ */
+typedef struct {
+    unsigned char data[32];
+} secp256k1_fixed_asset_tag;
+
+/** Returns the total number of inputs a proof expects to be over.
+ *
+ * Returns: the number of inputs for the given proof
+ * In:   ctx: pointer to a context object
+ *     proof: a pointer to a proof object
+ */
+SECP256K1_API size_t secp256k1_surjectionproof_n_total_inputs(
+  const secp256k1_context* ctx,
+  const secp256k1_surjectionproof* proof
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Returns the actual number of inputs that a proof uses
+ *
+ * Returns: the number of inputs for the given proof
+ * In:   ctx: pointer to a context object
+ *     proof: a pointer to a proof object
+ */
+SECP256K1_API size_t secp256k1_surjectionproof_n_used_inputs(
+  const secp256k1_context* ctx,
+  const secp256k1_surjectionproof* proof
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Returns the total size this proof would take, in bytes, when serialized
+ *
+ * Returns: the total size
+ * In:   ctx: pointer to a context object
+ *     proof: a pointer to a proof object
+ */
+SECP256K1_API size_t secp256k1_surjectionproof_serialized_size(
+  const secp256k1_context* ctx,
+  const secp256k1_surjectionproof* proof
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Surjection proof initialization function; decides on inputs to use
+ *  To be used to initialize stack-allocated secp256k1_surjectionproof struct
+ * Returns 0: inputs could not be selected
+ *         n: inputs were selected after n iterations of random selection
+ *
+ * In:               ctx: pointer to a context object
+ *      fixed_input_tags: fixed input tags `A_i` for all inputs. (If the fixed tag is not known,
+ *                        e.g. in a coinjoin with others' inputs, an ephemeral tag can be given;
+ *                        this won't match the output tag but might be used in the anonymity set.)
+ *          n_input_tags: the number of entries in the fixed_input_tags array
+ *      n_input_tags_to_use: the number of inputs to select randomly to put in the anonymity set
+ *      fixed_output_tag: fixed output tag
+ *      max_n_iterations: the maximum number of iterations to do before giving up. Because the
+ *                        maximum number of inputs (SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS) is
+ *                        limited to 256 the probability of giving up is smaller than
+ *                        (255/256)^(n_input_tags_to_use*max_n_iterations).
+ *
+ *         random_seed32: a random seed to be used for input selection
+ * Out:            proof: The proof whose bitvector will be initialized. In case of failure,
+ *                        the state of the proof is undefined.
+ *          input_index: The index of the actual input that is secretly mapped to the output
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_surjectionproof_initialize(
+  const secp256k1_context* ctx,
+  secp256k1_surjectionproof* proof,
+  size_t *input_index,
+  const secp256k1_fixed_asset_tag* fixed_input_tags,
+  const size_t n_input_tags,
+  const size_t n_input_tags_to_use,
+  const secp256k1_fixed_asset_tag* fixed_output_tag,
+  const size_t n_max_iterations,
+  const unsigned char *random_seed32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(7);
+
+
+/** Surjection proof allocation and initialization function; decides on inputs to use
+ * Returns 0: inputs could not be selected, or malloc failure
+ *         n: inputs were selected after n iterations of random selection
+ *
+ * In:               ctx: pointer to a context object
+ *           proof_out_p: a pointer to a pointer to `secp256k1_surjectionproof*`.
+ *                        the newly-allocated struct pointer will be saved here.
+ *      fixed_input_tags: fixed input tags `A_i` for all inputs. (If the fixed tag is not known,
+ *                        e.g. in a coinjoin with others' inputs, an ephemeral tag can be given;
+ *                        this won't match the output tag but might be used in the anonymity set.)
+ *          n_input_tags: the number of entries in the fixed_input_tags array
+ *      n_input_tags_to_use: the number of inputs to select randomly to put in the anonymity set
+ *      fixed_output_tag: fixed output tag
+ *      max_n_iterations: the maximum number of iterations to do before giving up. Because the
+ *                        maximum number of inputs (SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS) is
+ *                        limited to 256 the probability of giving up is smaller than
+ *                        (255/256)^(n_input_tags_to_use*max_n_iterations).
+ *
+ *         random_seed32: a random seed to be used for input selection
+ * Out:      proof_out_p: The pointer to newly-allocated proof whose bitvector will be initialized.
+ *                        In case of failure, the pointer will be NULL.
+ *          input_index: The index of the actual input that is secretly mapped to the output
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_surjectionproof_allocate_initialized(
+        const secp256k1_context* ctx,
+        secp256k1_surjectionproof** proof_out_p,
+        size_t *input_index,
+        const secp256k1_fixed_asset_tag* fixed_input_tags,
+        const size_t n_input_tags,
+        const size_t n_input_tags_to_use,
+        const secp256k1_fixed_asset_tag* fixed_output_tag,
+        const size_t n_max_iterations,
+        const unsigned char *random_seed32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(7);
+
+/** Surjection proof destroy function
+ *  deallocates the struct that was allocated with secp256k1_surjectionproof_allocate_initialized
+ *
+ * In:               proof: pointer to secp256k1_surjectionproof struct
+ */
+SECP256K1_API void secp256k1_surjectionproof_destroy(
+        secp256k1_surjectionproof* proof
+) SECP256K1_ARG_NONNULL(1);
+
+/** Surjection proof generation function
+ * Returns 0: proof could not be created
+ *         1: proof was successfully created
+ *
+ * In:                   ctx: pointer to a context object, initialized for signing and verification
+ *      ephemeral_input_tags: the ephemeral asset tag of all inputs
+ *    n_ephemeral_input_tags: the number of entries in the ephemeral_input_tags array
+ *      ephemeral_output_tag: the ephemeral asset tag of the output
+ *               input_index: the index of the input that actually maps to the output
+ *        input_blinding_key: the blinding key of the input
+ *       output_blinding_key: the blinding key of the output
+ * In/Out: proof: The produced surjection proof. Must have already gone through `secp256k1_surjectionproof_initialize`
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_surjectionproof_generate(
+  const secp256k1_context* ctx,
+  secp256k1_surjectionproof* proof,
+  const secp256k1_generator* ephemeral_input_tags,
+  size_t n_ephemeral_input_tags,
+  const secp256k1_generator* ephemeral_output_tag,
+  size_t input_index,
+  const unsigned char *input_blinding_key,
+  const unsigned char *output_blinding_key
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8);
+
+
+/** Surjection proof verification function
+ * Returns 0: proof was invalid
+ *         1: proof was valid
+ *
+ * In:     ctx: pointer to a context object, initialized for signing and verification
+ *         proof: proof to be verified
+ *      ephemeral_input_tags: the ephemeral asset tag of all inputs
+ *    n_ephemeral_input_tags: the number of entries in the ephemeral_input_tags array
+ *      ephemeral_output_tag: the ephemeral asset tag of the output
+ */
+SECP256K1_API int secp256k1_surjectionproof_verify(
+  const secp256k1_context* ctx,
+  const secp256k1_surjectionproof* proof,
+  const secp256k1_generator* ephemeral_input_tags,
+  size_t n_ephemeral_input_tags,
+  const secp256k1_generator* ephemeral_output_tag
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

include/secp256k1_whitelist.h

@@ -0,0 +1,152 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_WHITELIST_
+#define _SECP256K1_WHITELIST_
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define SECP256K1_WHITELIST_MAX_N_KEYS	256
+
+/** Opaque data structure that holds a parsed whitelist proof
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. Nor is
+ *  it guaranteed to have any particular size, nor that identical signatures
+ *  will have identical representation. (That is, memcmp may return nonzero
+ *  even for identical signatures.)
+ *
+ *  To obtain these properties, instead use secp256k1_whitelist_signature_parse
+ *  and secp256k1_whitelist_signature_serialize to encode/decode signatures
+ *  into a well-defined format.
+ *
+ *  The representation is exposed to allow creation of these objects on the
+ *  stack; please *do not* use these internals directly. To learn the number
+ *  of keys for a signature, use `secp256k1_whitelist_signature_n_keys`.
+ */
+typedef struct {
+    size_t n_keys;
+    /* e0, scalars */
+    unsigned char data[32 * (1 + SECP256K1_WHITELIST_MAX_N_KEYS)];
+} secp256k1_whitelist_signature;
+
+/** Parse a whitelist signature
+ *
+ *  Returns: 1 when the signature could be parsed, 0 otherwise.
+ *  Args: ctx:    a secp256k1 context object
+ *  Out:  sig:    a pointer to a signature object
+ *  In:   input:  a pointer to the array to parse
+ *    input_len:  the length of the above array
+ *
+ *  The signature must consist of a 1-byte n_keys value, followed by a 32-byte
+ *  big endian e0 value, followed by n_keys many 32-byte big endian s values.
+ *  If n_keys falls outside of [0..SECP256K1_WHITELIST_MAX_N_KEYS] the encoding
+ *  is invalid.
+ *
+ *  The total length of the input array must therefore be 33 + 32 * n_keys.
+ *  If the length `input_len` does not match this value, parsing will fail.
+ *
+ *  After the call, sig will always be initialized. If parsing failed or any
+ *  scalar values overflow or are zero, the resulting sig value is guaranteed
+ *  to fail validation for any set of keys.
+ */
+SECP256K1_API int secp256k1_whitelist_signature_parse(
+    const secp256k1_context* ctx,
+    secp256k1_whitelist_signature *sig,
+    const unsigned char *input,
+    size_t input_len
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Returns the number of keys a signature expects to have.
+ *
+ *  Returns: the number of keys for the given signature
+ *  In: sig: a pointer to a signature object
+ */
+SECP256K1_API size_t secp256k1_whitelist_signature_n_keys(
+    const secp256k1_whitelist_signature *sig
+) SECP256K1_ARG_NONNULL(1);
+
+/** Serialize a whitelist signature
+ *
+ *  Returns: 1
+ *  Args:   ctx:        a secp256k1 context object
+ *  Out:    output64:   a pointer to an array to store the serialization
+ *  In/Out: output_len: length of the above array, updated with the actual serialized length
+ *  In:     sig:        a pointer to an initialized signature object
+ *
+ *  See secp256k1_whitelist_signature_parse for details about the encoding.
+ */
+SECP256K1_API int secp256k1_whitelist_signature_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *output,
+    size_t *output_len,
+    const secp256k1_whitelist_signature *sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Compute a whitelist signature
+ * Returns 1: signature was successfully created
+ *         0: signature was not successfully created
+ * In:     ctx: pointer to a context object, initialized for signing and verification
+ *         online_pubkeys: list of all online pubkeys
+ *         offline_pubkeys: list of all offline pubkeys
+ *         n_keys: the number of entries in each of the above two arrays
+ *         sub_pubkey: the key to be whitelisted
+ *         online_seckey: the secret key to the signer's online pubkey
+ *         summed_seckey: the secret key to the sum of (whitelisted key, signer's offline pubkey)
+ *         index: the signer's index in the lists of keys
+ *         noncefp:pointer to a nonce generation function. If NULL, secp256k1_nonce_function_default is used
+ *         ndata:  pointer to arbitrary data used by the nonce generation function (can be NULL)
+ * Out:    sig: The produced signature.
+ *
+ * The signatures are of the list of all passed pubkeys in the order
+ *     ( whitelist, online_1, offline_1, online_2, offline_2, ... )
+ * The verification key list consists of
+ *     online_i + H(offline_i + whitelist)(offline_i + whitelist)
+ * for each public key pair (offline_i, offline_i). Here H means sha256 of the
+ * compressed serialization of the key.
+ */
+SECP256K1_API int secp256k1_whitelist_sign(
+  const secp256k1_context* ctx,
+  secp256k1_whitelist_signature *sig,
+  const secp256k1_pubkey *online_pubkeys,
+  const secp256k1_pubkey *offline_pubkeys,
+  const size_t n_keys,
+  const secp256k1_pubkey *sub_pubkey,
+  const unsigned char *online_seckey,
+  const unsigned char *summed_seckey,
+  const size_t index,
+  secp256k1_nonce_function noncefp,
+  const void *noncedata
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8);
+
+/** Verify a whitelist signature
+ * Returns 1: signature is valid
+ *         0: signature is not valid
+ * In:     ctx: pointer to a context object, initialized for signing and verification
+ *         sig: the signature to be verified
+ *         online_pubkeys: list of all online pubkeys
+ *         offline_pubkeys: list of all offline pubkeys
+ *         n_keys: the number of entries in each of the above two arrays
+ *         sub_pubkey: the key to be whitelisted
+ */
+SECP256K1_API int secp256k1_whitelist_verify(
+  const secp256k1_context* ctx,
+  const secp256k1_whitelist_signature *sig,
+  const secp256k1_pubkey *online_pubkeys,
+  const secp256k1_pubkey *offline_pubkeys,
+  const size_t n_keys,
+  const secp256k1_pubkey *sub_pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(6);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

sage/shallue_van_de_woestijne.sage

@@ -0,0 +1,51 @@
+
+### http://www.di.ens.fr/~fouque/pub/latincrypt12.pdf
+
+# Parameters for secp256k1
+p = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F
+a = 0
+b = 7
+F = FiniteField (p)
+C = EllipticCurve ([F(a), F(b)])
+
+def svdw(t):
+    sqrt_neg_3 = F(-3).nth_root(2)
+
+    ## Compute candidate x values
+    w  = sqrt_neg_3 * t / (1 + b + t^2)
+    x = [ F(0), F(0), F(0) ]
+    x[0] = (-1 + sqrt_neg_3) / 2 - t * w
+    x[1] = -1 - x[0]
+    x[2] = 1 + 1 / w^2
+
+    print
+    print "On %2d" % t
+    print " x1 %064x" % x[0]
+    print " x2 %064x" % x[1]
+    print " x3 %064x" % x[2]
+
+    ## Select which to use
+    alph = jacobi_symbol(x[0]^3 + b, p)
+    beta = jacobi_symbol(x[1]^3 + b, p)
+    if alph == 1 and beta == 1:
+        i = 0
+    elif alph == 1 and beta == -1:
+        i = 0
+    elif alph == -1 and beta == 1:
+        i = 1
+    elif alph == -1 and beta == -1:
+        i = 2
+    else:
+        print "Help! I don't understand Python!"
+
+    ## Expand to full point
+    sign = 1 - 2 * (int(F(t)) % 2)
+    ret_x = x[i]
+    ret_y = sign * F(x[i]^3 + b).nth_root(2)
+    return C.point((ret_x, ret_y))
+
+
+## main
+for i in range(1, 11):
+    res = svdw(i)
+    print "Result: %064x %064x" % res.xy()

src/bench_generator.c

@@ -0,0 +1,59 @@
+/**********************************************************************
+ * Copyright (c) 2016 Pieter Wuille                                   *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#include <stdint.h>
+#include <string.h>
+
+#include "include/secp256k1_generator.h"
+#include "util.h"
+#include "bench.h"
+
+typedef struct {
+    secp256k1_context* ctx;
+    unsigned char key[32];
+    unsigned char blind[32];
+} bench_generator_t;
+
+static void bench_generator_setup(void* arg) {
+    bench_generator_t *data = (bench_generator_t*)arg;
+    memset(data->key, 0x31, 32);
+    memset(data->blind, 0x13, 32);
+}
+
+static void bench_generator_generate(void* arg) {
+    int i;
+    bench_generator_t *data = (bench_generator_t*)arg;
+
+    for (i = 0; i < 20000; i++) {
+        secp256k1_generator gen;
+        CHECK(secp256k1_generator_generate(data->ctx, &gen, data->key));
+        data->key[i & 31]++;
+    }
+}
+
+static void bench_generator_generate_blinded(void* arg) {
+    int i;
+    bench_generator_t *data = (bench_generator_t*)arg;
+
+    for (i = 0; i < 20000; i++) {
+        secp256k1_generator gen;
+        CHECK(secp256k1_generator_generate_blinded(data->ctx, &gen, data->key, data->blind));
+        data->key[1 + (i & 30)]++;
+        data->blind[1 + (i & 30)]++;
+    }
+}
+
+int main(void) {
+    bench_generator_t data;
+
+    data.ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+
+    run_benchmark("generator_generate", bench_generator_generate, bench_generator_setup, NULL, &data, 10, 20000);
+    run_benchmark("generator_generate_blinded", bench_generator_generate_blinded, bench_generator_setup, NULL, &data, 10, 20000);
+
+    secp256k1_context_destroy(data.ctx);
+    return 0;
+}

src/bench_rangeproof.c

@@ -0,0 +1,63 @@
+/**********************************************************************
+ * Copyright (c) 2014, 2015 Pieter Wuille, Gregory Maxwell            *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#include <stdint.h>
+
+#include "include/secp256k1_rangeproof.h"
+#include "util.h"
+#include "bench.h"
+
+typedef struct {
+    secp256k1_context* ctx;
+    secp256k1_pedersen_commitment commit;
+    unsigned char proof[5134];
+    unsigned char blind[32];
+    size_t len;
+    int min_bits;
+    uint64_t v;
+} bench_rangeproof_t;
+
+static void bench_rangeproof_setup(void* arg) {
+    int i;
+    uint64_t minv;
+    uint64_t maxv;
+    bench_rangeproof_t *data = (bench_rangeproof_t*)arg;
+
+    data->v = 0;
+    for (i = 0; i < 32; i++) data->blind[i] = i + 1;
+    CHECK(secp256k1_pedersen_commit(data->ctx, &data->commit, data->blind, data->v, secp256k1_generator_h));
+    data->len = 5134;
+    CHECK(secp256k1_rangeproof_sign(data->ctx, data->proof, &data->len, 0, &data->commit, data->blind, (const unsigned char*)&data->commit, 0, data->min_bits, data->v, NULL, 0, NULL, 0, secp256k1_generator_h));
+    CHECK(secp256k1_rangeproof_verify(data->ctx, &minv, &maxv, &data->commit, data->proof, data->len, NULL, 0, secp256k1_generator_h));
+}
+
+static void bench_rangeproof(void* arg) {
+    int i;
+    bench_rangeproof_t *data = (bench_rangeproof_t*)arg;
+
+    for (i = 0; i < 1000; i++) {
+        int j;
+        uint64_t minv;
+        uint64_t maxv;
+        j = secp256k1_rangeproof_verify(data->ctx, &minv, &maxv, &data->commit, data->proof, data->len, NULL, 0, secp256k1_generator_h);
+        for (j = 0; j < 4; j++) {
+            data->proof[j + 2 + 32 *((data->min_bits + 1) >> 1) - 4] = (i >> 8)&255;
+        }
+    }
+}
+
+int main(void) {
+    bench_rangeproof_t data;
+
+    data.ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+
+    data.min_bits = 32;
+
+    run_benchmark("rangeproof_verify_bit", bench_rangeproof, bench_rangeproof_setup, NULL, &data, 10, 1000 * data.min_bits);
+
+    secp256k1_context_destroy(data.ctx);
+    return 0;
+}

src/bench_schnorrsig.c

@@ -0,0 +1,128 @@
+/**********************************************************************
+ * Copyright (c) 2018 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "include/secp256k1.h"
+#include "include/secp256k1_schnorrsig.h"
+#include "util.h"
+#include "bench.h"
+
+#define MAX_SIGS	(32768)
+
+typedef struct {
+    secp256k1_context *ctx;
+    secp256k1_scratch_space *scratch;
+    size_t n;
+    const unsigned char **pk;
+    const secp256k1_schnorrsig **sigs;
+    const unsigned char **msgs;
+} bench_schnorrsig_data;
+
+void bench_schnorrsig_sign(void* arg) {
+    bench_schnorrsig_data *data = (bench_schnorrsig_data *)arg;
+    size_t i;
+    unsigned char sk[32] = "benchmarkexample secrettemplate";
+    unsigned char msg[32] = "benchmarkexamplemessagetemplate";
+    secp256k1_schnorrsig sig;
+
+    for (i = 0; i < 1000; i++) {
+        msg[0] = i;
+        msg[1] = i >> 8;
+        sk[0] = i;
+        sk[1] = i >> 8;
+        CHECK(secp256k1_schnorrsig_sign(data->ctx, &sig, NULL, msg, sk, NULL, NULL));
+    }
+}
+
+void bench_schnorrsig_verify(void* arg) {
+    bench_schnorrsig_data *data = (bench_schnorrsig_data *)arg;
+    size_t i;
+
+    for (i = 0; i < 1000; i++) {
+        secp256k1_pubkey pk;
+        CHECK(secp256k1_ec_pubkey_parse(data->ctx, &pk, data->pk[i], 33) == 1);
+        CHECK(secp256k1_schnorrsig_verify(data->ctx, data->sigs[i], data->msgs[i], &pk));
+    }
+}
+
+void bench_schnorrsig_verify_n(void* arg) {
+    bench_schnorrsig_data *data = (bench_schnorrsig_data *)arg;
+    size_t i, j;
+    const secp256k1_pubkey **pk = (const secp256k1_pubkey **)malloc(data->n * sizeof(*pk));
+
+    CHECK(pk != NULL);
+    for (j = 0; j < MAX_SIGS/data->n; j++) {
+        for (i = 0; i < data->n; i++) {
+            secp256k1_pubkey *pk_nonconst = (secp256k1_pubkey *)malloc(sizeof(*pk_nonconst));
+            CHECK(secp256k1_ec_pubkey_parse(data->ctx, pk_nonconst, data->pk[i], 33) == 1);
+            pk[i] = pk_nonconst;
+        }
+        CHECK(secp256k1_schnorrsig_verify_batch(data->ctx, data->scratch, data->sigs, data->msgs, pk, data->n));
+        for (i = 0; i < data->n; i++) {
+            free((void *)pk[i]);
+        }
+    }
+    free(pk);
+}
+
+int main(void) {
+    size_t i;
+    bench_schnorrsig_data data;
+
+    data.ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY | SECP256K1_CONTEXT_SIGN);
+    data.scratch = secp256k1_scratch_space_create(data.ctx, 1024 * 1024 * 1024);
+    data.pk = (const unsigned char **)malloc(MAX_SIGS * sizeof(unsigned char *));
+    data.msgs = (const unsigned char **)malloc(MAX_SIGS * sizeof(unsigned char *));
+    data.sigs = (const secp256k1_schnorrsig **)malloc(MAX_SIGS * sizeof(secp256k1_schnorrsig *));
+
+    for (i = 0; i < MAX_SIGS; i++) {
+        unsigned char sk[32];
+        unsigned char *msg = (unsigned char *)malloc(32);
+        secp256k1_schnorrsig *sig = (secp256k1_schnorrsig *)malloc(sizeof(*sig));
+        unsigned char *pk_char = (unsigned char *)malloc(33);
+        secp256k1_pubkey pk;
+        size_t pk_len = 33;
+        msg[0] = sk[0] = i;
+        msg[1] = sk[1] = i >> 8;
+        msg[2] = sk[2] = i >> 16;
+        msg[3] = sk[3] = i >> 24;
+        memset(&msg[4], 'm', 28);
+        memset(&sk[4], 's', 28);
+
+        data.pk[i] = pk_char;
+        data.msgs[i] = msg;
+        data.sigs[i] = sig;
+
+        CHECK(secp256k1_ec_pubkey_create(data.ctx, &pk, sk));
+        CHECK(secp256k1_ec_pubkey_serialize(data.ctx, pk_char, &pk_len, &pk, SECP256K1_EC_COMPRESSED) == 1);
+        CHECK(secp256k1_schnorrsig_sign(data.ctx, sig, NULL, msg, sk, NULL, NULL));
+    }
+
+    run_benchmark("schnorrsig_sign", bench_schnorrsig_sign, NULL, NULL, (void *) &data, 10, 1000);
+    run_benchmark("schnorrsig_verify", bench_schnorrsig_verify, NULL, NULL, (void *) &data, 10, 1000);
+    for (i = 1; i <= MAX_SIGS; i *= 2) {
+        char name[64];
+        sprintf(name, "schnorrsig_batch_verify_%d", (int) i);
+
+        data.n = i;
+        run_benchmark(name, bench_schnorrsig_verify_n, NULL, NULL, (void *) &data, 3, MAX_SIGS);
+    }
+
+    for (i = 0; i < MAX_SIGS; i++) {
+        free((void *)data.pk[i]);
+        free((void *)data.msgs[i]);
+        free((void *)data.sigs[i]);
+    }
+    free(data.pk);
+    free(data.msgs);
+    free(data.sigs);
+
+    secp256k1_scratch_space_destroy(data.scratch);
+    secp256k1_context_destroy(data.ctx);
+    return 0;
+}

src/bench_whitelist.c

@@ -0,0 +1,104 @@
+/**********************************************************************
+ * Copyright (c) 2017 Jonas Nick                                      *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+#include <stdio.h>
+
+#include "include/secp256k1.h"
+
+#include "include/secp256k1_whitelist.h"
+#include "bench.h"
+#include "util.h"
+#include "hash_impl.h"
+#include "num_impl.h"
+#include "scalar_impl.h"
+#include "testrand_impl.h"
+
+#define MAX_N_KEYS 30
+
+typedef struct {
+    secp256k1_context* ctx;
+    unsigned char online_seckey[MAX_N_KEYS][32];
+    unsigned char summed_seckey[MAX_N_KEYS][32];
+    secp256k1_pubkey online_pubkeys[MAX_N_KEYS];
+    secp256k1_pubkey offline_pubkeys[MAX_N_KEYS];
+    unsigned char csub[32];
+    secp256k1_pubkey sub_pubkey;
+    secp256k1_whitelist_signature sig;
+    size_t n_keys;
+} bench_data;
+
+static void bench_whitelist(void* arg) {
+    bench_data* data = (bench_data*)arg;
+    CHECK(secp256k1_whitelist_verify(data->ctx, &data->sig, data->online_pubkeys, data->offline_pubkeys, data->n_keys, &data->sub_pubkey) == 1);
+}
+
+static void bench_whitelist_setup(void* arg) {
+    bench_data* data = (bench_data*)arg;
+    int i = 0;
+    CHECK(secp256k1_whitelist_sign(data->ctx, &data->sig, data->online_pubkeys, data->offline_pubkeys, data->n_keys, &data->sub_pubkey, data->online_seckey[i], data->summed_seckey[i], i, NULL, NULL));
+}
+
+static void run_test(bench_data* data) {
+    char str[32];
+    sprintf(str, "whitelist_%i", (int)data->n_keys);
+    run_benchmark(str, bench_whitelist, bench_whitelist_setup, NULL, data, 100, 1);
+}
+
+void random_scalar_order(secp256k1_scalar *num) {
+    do {
+        unsigned char b32[32];
+        int overflow = 0;
+        secp256k1_rand256(b32);
+        secp256k1_scalar_set_b32(num, b32, &overflow);
+        if (overflow || secp256k1_scalar_is_zero(num)) {
+            continue;
+        }
+        break;
+    } while(1);
+}
+
+int main(void) {
+    bench_data data;
+    size_t i;
+    size_t n_keys = 30;
+    secp256k1_scalar ssub;
+
+    data.ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+
+    /* Start with subkey */
+    random_scalar_order(&ssub);
+    secp256k1_scalar_get_b32(data.csub, &ssub);
+    CHECK(secp256k1_ec_seckey_verify(data.ctx, data.csub) == 1);
+    CHECK(secp256k1_ec_pubkey_create(data.ctx, &data.sub_pubkey, data.csub) == 1);
+    /* Then offline and online whitelist keys */
+    for (i = 0; i < n_keys; i++) {
+        secp256k1_scalar son, soff;
+
+        /* Create two keys */
+        random_scalar_order(&son);
+        secp256k1_scalar_get_b32(data.online_seckey[i], &son);
+        CHECK(secp256k1_ec_seckey_verify(data.ctx, data.online_seckey[i]) == 1);
+        CHECK(secp256k1_ec_pubkey_create(data.ctx, &data.online_pubkeys[i], data.online_seckey[i]) == 1);
+
+        random_scalar_order(&soff);
+        secp256k1_scalar_get_b32(data.summed_seckey[i], &soff);
+        CHECK(secp256k1_ec_seckey_verify(data.ctx, data.summed_seckey[i]) == 1);
+        CHECK(secp256k1_ec_pubkey_create(data.ctx, &data.offline_pubkeys[i], data.summed_seckey[i]) == 1);
+
+        /* Make summed_seckey correspond to the sum of offline_pubkey and sub_pubkey */
+        secp256k1_scalar_add(&soff, &soff, &ssub);
+        secp256k1_scalar_get_b32(data.summed_seckey[i], &soff);
+        CHECK(secp256k1_ec_seckey_verify(data.ctx, data.summed_seckey[i]) == 1);
+    }
+
+    /* Run test */
+    for (i = 1; i <= n_keys; ++i) {
+        data.n_keys = i;
+        run_test(&data);
+    }
+
+    secp256k1_context_destroy(data.ctx);
+    return(0);
+}

src/modules/generator/Makefile.am.include

@@ -0,0 +1,9 @@
+include_HEADERS += include/secp256k1_generator.h
+noinst_HEADERS += src/modules/generator/main_impl.h
+noinst_HEADERS += src/modules/generator/tests_impl.h
+if USE_BENCHMARK
+noinst_PROGRAMS += bench_generator
+bench_generator_SOURCES = src/bench_generator.c
+bench_generator_LDADD = libsecp256k1.la $(SECP_LIBS)
+bench_generator_LDFLAGS = -static
+endif

src/modules/generator/main_impl.h

@@ -0,0 +1,222 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra & Pieter Wuille                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_GENERATOR_MAIN
+#define SECP256K1_MODULE_GENERATOR_MAIN
+
+#include <stdio.h>
+
+#include "field.h"
+#include "group.h"
+#include "hash.h"
+#include "scalar.h"
+
+static void secp256k1_generator_load(secp256k1_ge* ge, const secp256k1_generator* gen) {
+    int succeed;
+    succeed = secp256k1_fe_set_b32(&ge->x, &gen->data[0]);
+    VERIFY_CHECK(succeed != 0);
+    succeed = secp256k1_fe_set_b32(&ge->y, &gen->data[32]);
+    VERIFY_CHECK(succeed != 0);
+    ge->infinity = 0;
+    (void) succeed;
+}
+
+static void secp256k1_generator_save(secp256k1_generator *gen, secp256k1_ge* ge) {
+    VERIFY_CHECK(!secp256k1_ge_is_infinity(ge));
+    secp256k1_fe_normalize_var(&ge->x);
+    secp256k1_fe_normalize_var(&ge->y);
+    secp256k1_fe_get_b32(&gen->data[0], &ge->x);
+    secp256k1_fe_get_b32(&gen->data[32], &ge->y);
+}
+
+int secp256k1_generator_parse(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *input) {
+    secp256k1_fe x;
+    secp256k1_ge ge;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(input != NULL);
+
+    if ((input[0] & 0xFE) != 10 ||
+        !secp256k1_fe_set_b32(&x, &input[1]) ||
+        !secp256k1_ge_set_xquad(&ge, &x)) {
+        return 0;
+    }
+    if (input[0] & 1) {
+        secp256k1_ge_neg(&ge, &ge);
+    }
+    secp256k1_generator_save(gen, &ge);
+    return 1;
+}
+
+int secp256k1_generator_serialize(const secp256k1_context* ctx, unsigned char *output, const secp256k1_generator* gen) {
+    secp256k1_ge ge;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(output != NULL);
+    ARG_CHECK(gen != NULL);
+
+    secp256k1_generator_load(&ge, gen);
+
+    output[0] = 11 ^ secp256k1_fe_is_quad_var(&ge.y);
+    secp256k1_fe_normalize_var(&ge.x);
+    secp256k1_fe_get_b32(&output[1], &ge.x);
+    return 1;
+}
+
+static void shallue_van_de_woestijne(secp256k1_ge* ge, const secp256k1_fe* t) {
+    /* Implements the algorithm from:
+     *    Indifferentiable Hashing to Barreto-Naehrig Curves
+     *    Pierre-Alain Fouque and Mehdi Tibouchi
+     *    Latincrypt 2012
+     */
+
+    /* Basic algorithm:
+
+       c = sqrt(-3)
+       d = (c - 1)/2
+
+       w = c * t / (1 + b + t^2)  [with b = 7]
+       x1 = d - t*w
+       x2 = -(x1 + 1)
+       x3 = 1 + 1/w^2
+
+       To avoid the 2 divisions, compute the above in numerator/denominator form:
+       wn = c * t
+       wd = 1 + 7 + t^2
+       x1n = d*wd - t*wn
+       x1d = wd
+       x2n = -(x1n + wd)
+       x2d = wd
+       x3n = wd^2 + c^2 + t^2
+       x3d = (c * t)^2
+
+       The joint denominator j = wd * c^2 * t^2, and
+       1 / x1d = 1/j * c^2 * t^2
+       1 / x2d = x3d = 1/j * wd
+    */
+
+    static const secp256k1_fe c = SECP256K1_FE_CONST(0x0a2d2ba9, 0x3507f1df, 0x233770c2, 0xa797962c, 0xc61f6d15, 0xda14ecd4, 0x7d8d27ae, 0x1cd5f852);
+    static const secp256k1_fe d = SECP256K1_FE_CONST(0x851695d4, 0x9a83f8ef, 0x919bb861, 0x53cbcb16, 0x630fb68a, 0xed0a766a, 0x3ec693d6, 0x8e6afa40);
+    static const secp256k1_fe b = SECP256K1_FE_CONST(0, 0, 0, 0, 0, 0, 0, 7);
+    static const secp256k1_fe b_plus_one = SECP256K1_FE_CONST(0, 0, 0, 0, 0, 0, 0, 8);
+
+    secp256k1_fe wn, wd, x1n, x2n, x3n, x3d, jinv, tmp, x1, x2, x3, alphain, betain, gammain, y1, y2, y3;
+    int alphaquad, betaquad;
+
+    secp256k1_fe_mul(&wn, &c, t); /* mag 1 */
+    secp256k1_fe_sqr(&wd, t); /* mag 1 */
+    secp256k1_fe_add(&wd, &b_plus_one); /* mag 2 */
+    secp256k1_fe_mul(&tmp, t, &wn); /* mag 1 */
+    secp256k1_fe_negate(&tmp, &tmp, 1); /* mag 2 */
+    secp256k1_fe_mul(&x1n, &d, &wd); /* mag 1 */
+    secp256k1_fe_add(&x1n, &tmp); /* mag 3 */
+    x2n = x1n; /* mag 3 */
+    secp256k1_fe_add(&x2n, &wd); /* mag 5 */
+    secp256k1_fe_negate(&x2n, &x2n, 5); /* mag 6 */
+    secp256k1_fe_mul(&x3d, &c, t); /* mag 1 */
+    secp256k1_fe_sqr(&x3d, &x3d); /* mag 1 */
+    secp256k1_fe_sqr(&x3n, &wd); /* mag 1 */
+    secp256k1_fe_add(&x3n, &x3d); /* mag 2 */
+    secp256k1_fe_mul(&jinv, &x3d, &wd); /* mag 1 */
+    secp256k1_fe_inv(&jinv, &jinv); /* mag 1 */
+    secp256k1_fe_mul(&x1, &x1n, &x3d); /* mag 1 */
+    secp256k1_fe_mul(&x1, &x1, &jinv); /* mag 1 */
+    secp256k1_fe_mul(&x2, &x2n, &x3d); /* mag 1 */
+    secp256k1_fe_mul(&x2, &x2, &jinv); /* mag 1 */
+    secp256k1_fe_mul(&x3, &x3n, &wd); /* mag 1 */
+    secp256k1_fe_mul(&x3, &x3, &jinv); /* mag 1 */
+
+    secp256k1_fe_sqr(&alphain, &x1); /* mag 1 */
+    secp256k1_fe_mul(&alphain, &alphain, &x1); /* mag 1 */
+    secp256k1_fe_add(&alphain, &b); /* mag 2 */
+    secp256k1_fe_sqr(&betain, &x2); /* mag 1 */
+    secp256k1_fe_mul(&betain, &betain, &x2); /* mag 1 */
+    secp256k1_fe_add(&betain, &b); /* mag 2 */
+    secp256k1_fe_sqr(&gammain, &x3); /* mag 1 */
+    secp256k1_fe_mul(&gammain, &gammain, &x3); /* mag 1 */
+    secp256k1_fe_add(&gammain, &b); /* mag 2 */
+
+    alphaquad = secp256k1_fe_sqrt(&y1, &alphain);
+    betaquad = secp256k1_fe_sqrt(&y2, &betain);
+    secp256k1_fe_sqrt(&y3, &gammain);
+
+    secp256k1_fe_cmov(&x1, &x2, (!alphaquad) & betaquad);
+    secp256k1_fe_cmov(&y1, &y2, (!alphaquad) & betaquad);
+    secp256k1_fe_cmov(&x1, &x3, (!alphaquad) & !betaquad);
+    secp256k1_fe_cmov(&y1, &y3, (!alphaquad) & !betaquad);
+
+    secp256k1_ge_set_xy(ge, &x1, &y1);
+
+    /* The linked algorithm from the paper uses the Jacobi symbol of t to
+     * determine the Jacobi symbol of the produced y coordinate. Since the
+     * rest of the algorithm only uses t^2, we can safely use another criterion
+     * as long as negation of t results in negation of the y coordinate. Here
+     * we choose to use t's oddness, as it is faster to determine. */
+    secp256k1_fe_negate(&tmp, &ge->y, 1);
+    secp256k1_fe_cmov(&ge->y, &tmp, secp256k1_fe_is_odd(t));
+}
+
+static int secp256k1_generator_generate_internal(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *key32, const unsigned char *blind32) {
+    static const unsigned char prefix1[17] = "1st generation: ";
+    static const unsigned char prefix2[17] = "2nd generation: ";
+    secp256k1_fe t = SECP256K1_FE_CONST(0, 0, 0, 0, 0, 0, 0, 4);
+    secp256k1_ge add;
+    secp256k1_gej accum;
+    int overflow;
+    secp256k1_sha256 sha256;
+    unsigned char b32[32];
+    int ret = 1;
+
+    if (blind32) {
+        secp256k1_scalar blind;
+        secp256k1_scalar_set_b32(&blind, blind32, &overflow);
+        ret = !overflow;
+        secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &accum, &blind);
+    }
+
+    secp256k1_sha256_initialize(&sha256);
+    secp256k1_sha256_write(&sha256, prefix1, 16);
+    secp256k1_sha256_write(&sha256, key32, 32);
+    secp256k1_sha256_finalize(&sha256, b32);
+    ret &= secp256k1_fe_set_b32(&t, b32);
+    shallue_van_de_woestijne(&add, &t);
+    if (blind32) {
+        secp256k1_gej_add_ge(&accum, &accum, &add);
+    } else {
+        secp256k1_gej_set_ge(&accum, &add);
+    }
+
+    secp256k1_sha256_initialize(&sha256);
+    secp256k1_sha256_write(&sha256, prefix2, 16);
+    secp256k1_sha256_write(&sha256, key32, 32);
+    secp256k1_sha256_finalize(&sha256, b32);
+    ret &= secp256k1_fe_set_b32(&t, b32);
+    shallue_van_de_woestijne(&add, &t);
+    secp256k1_gej_add_ge(&accum, &accum, &add);
+
+    secp256k1_ge_set_gej(&add, &accum);
+    secp256k1_generator_save(gen, &add);
+    return ret;
+}
+
+int secp256k1_generator_generate(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *key32) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(key32 != NULL);
+    return secp256k1_generator_generate_internal(ctx, gen, key32, NULL);
+}
+
+int secp256k1_generator_generate_blinded(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *key32, const unsigned char *blind32) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(key32 != NULL);
+    ARG_CHECK(blind32 != NULL);
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    return secp256k1_generator_generate_internal(ctx, gen, key32, blind32);
+}
+
+#endif

src/modules/generator/tests_impl.h

@@ -0,0 +1,227 @@
+/**********************************************************************
+ * Copyright (c) 2016 Pieter Wuille                                   *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_GENERATOR_TESTS
+#define SECP256K1_MODULE_GENERATOR_TESTS
+
+#include <string.h>
+#include <stdio.h>
+
+#include "group.h"
+#include "scalar.h"
+#include "testrand.h"
+#include "util.h"
+
+#include "include/secp256k1_generator.h"
+
+void test_generator_api(void) {
+    unsigned char key[32];
+    unsigned char blind[32];
+    unsigned char sergen[33];
+    secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
+    secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    secp256k1_generator gen;
+    int32_t ecount = 0;
+
+    secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_rand256(key);
+    secp256k1_rand256(blind);
+
+    CHECK(secp256k1_generator_generate(none, &gen, key) == 1);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_generator_generate(none, NULL, key) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_generator_generate(none, &gen, NULL) == 0);
+    CHECK(ecount == 2);
+
+    CHECK(secp256k1_generator_generate_blinded(sign, &gen, key, blind) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_generator_generate_blinded(vrfy, &gen, key, blind) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_generator_generate_blinded(none, &gen, key, blind) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_generator_generate_blinded(vrfy, NULL, key, blind) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_generator_generate_blinded(vrfy, &gen, NULL, blind) == 0);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_generator_generate_blinded(vrfy, &gen, key, NULL) == 0);
+    CHECK(ecount == 7);
+
+    CHECK(secp256k1_generator_serialize(none, sergen, &gen) == 1);
+    CHECK(ecount == 7);
+    CHECK(secp256k1_generator_serialize(none, NULL, &gen) == 0);
+    CHECK(ecount == 8);
+    CHECK(secp256k1_generator_serialize(none, sergen, NULL) == 0);
+    CHECK(ecount == 9);
+
+    CHECK(secp256k1_generator_serialize(none, sergen, &gen) == 1);
+    CHECK(secp256k1_generator_parse(none, &gen, sergen) == 1);
+    CHECK(ecount == 9);
+    CHECK(secp256k1_generator_parse(none, NULL, sergen) == 0);
+    CHECK(ecount == 10);
+    CHECK(secp256k1_generator_parse(none, &gen, NULL) == 0);
+    CHECK(ecount == 11);
+
+    secp256k1_context_destroy(none);
+    secp256k1_context_destroy(sign);
+    secp256k1_context_destroy(vrfy);
+}
+
+void test_shallue_van_de_woestijne(void) {
+    /* Matches with the output of the shallue_van_de_woestijne.sage SAGE program */
+    static const secp256k1_ge_storage results[32] = {
+        SECP256K1_GE_STORAGE_CONST(0xedd1fd3e, 0x327ce90c, 0xc7a35426, 0x14289aee, 0x9682003e, 0x9cf7dcc9, 0xcf2ca974, 0x3be5aa0c, 0x0225f529, 0xee75acaf, 0xccfc4560, 0x26c5e46b, 0xf80237a3, 0x3924655a, 0x16f90e88, 0x085ed52a),
+        SECP256K1_GE_STORAGE_CONST(0xedd1fd3e, 0x327ce90c, 0xc7a35426, 0x14289aee, 0x9682003e, 0x9cf7dcc9, 0xcf2ca974, 0x3be5aa0c, 0xfdda0ad6, 0x118a5350, 0x3303ba9f, 0xd93a1b94, 0x07fdc85c, 0xc6db9aa5, 0xe906f176, 0xf7a12705),
+        SECP256K1_GE_STORAGE_CONST(0x2c5cdc9c, 0x338152fa, 0x85de92cb, 0x1bee9907, 0x765a922e, 0x4f037cce, 0x14ecdbf2, 0x2f78fe15, 0x56716069, 0x6818286b, 0x72f01a3e, 0x5e8caca7, 0x36249160, 0xc7ded69d, 0xd51913c3, 0x03a2fa97),
+        SECP256K1_GE_STORAGE_CONST(0x2c5cdc9c, 0x338152fa, 0x85de92cb, 0x1bee9907, 0x765a922e, 0x4f037cce, 0x14ecdbf2, 0x2f78fe15, 0xa98e9f96, 0x97e7d794, 0x8d0fe5c1, 0xa1735358, 0xc9db6e9f, 0x38212962, 0x2ae6ec3b, 0xfc5d0198),
+        SECP256K1_GE_STORAGE_CONST(0x531f7239, 0xaebc780e, 0x179fbf8d, 0x412a1b01, 0x511f0abc, 0xe0c46151, 0x8b38db84, 0xcc2467f3, 0x82387d45, 0xec7bd5cc, 0x61fcb9df, 0x41cddd7b, 0x217d8114, 0x3577dc8f, 0x23de356a, 0x7e97704e),
+        SECP256K1_GE_STORAGE_CONST(0x531f7239, 0xaebc780e, 0x179fbf8d, 0x412a1b01, 0x511f0abc, 0xe0c46151, 0x8b38db84, 0xcc2467f3, 0x7dc782ba, 0x13842a33, 0x9e034620, 0xbe322284, 0xde827eeb, 0xca882370, 0xdc21ca94, 0x81688be1),
+        SECP256K1_GE_STORAGE_CONST(0x2c5cdc9c, 0x338152fa, 0x85de92cb, 0x1bee9907, 0x765a922e, 0x4f037cce, 0x14ecdbf2, 0x2f78fe15, 0x56716069, 0x6818286b, 0x72f01a3e, 0x5e8caca7, 0x36249160, 0xc7ded69d, 0xd51913c3, 0x03a2fa97),
+        SECP256K1_GE_STORAGE_CONST(0x2c5cdc9c, 0x338152fa, 0x85de92cb, 0x1bee9907, 0x765a922e, 0x4f037cce, 0x14ecdbf2, 0x2f78fe15, 0xa98e9f96, 0x97e7d794, 0x8d0fe5c1, 0xa1735358, 0xc9db6e9f, 0x38212962, 0x2ae6ec3b, 0xfc5d0198),
+        SECP256K1_GE_STORAGE_CONST(0x5e5936b1, 0x81db0b65, 0x8e33a8c6, 0x1aa687dd, 0x31d11e15, 0x85e35664, 0x6b4c2071, 0xcde7e942, 0x88bb5332, 0xa8e05654, 0x78d4f60c, 0x0cd979ec, 0x938558f2, 0xcac11216, 0x7c387a56, 0xe3a6d5f3),
+        SECP256K1_GE_STORAGE_CONST(0x5e5936b1, 0x81db0b65, 0x8e33a8c6, 0x1aa687dd, 0x31d11e15, 0x85e35664, 0x6b4c2071, 0xcde7e942, 0x7744accd, 0x571fa9ab, 0x872b09f3, 0xf3268613, 0x6c7aa70d, 0x353eede9, 0x83c785a8, 0x1c59263c),
+        SECP256K1_GE_STORAGE_CONST(0x657d438f, 0xfac34a50, 0x463fd07c, 0x3f09f320, 0x4c98e8ed, 0x6927e330, 0xc0c7735f, 0x76d32f6d, 0x577c2b11, 0xcaca2f6f, 0xd60bcaf0, 0x3e7cebe9, 0x5da6e1f4, 0xbb557f12, 0x2a397331, 0x81df897f),
+        SECP256K1_GE_STORAGE_CONST(0x657d438f, 0xfac34a50, 0x463fd07c, 0x3f09f320, 0x4c98e8ed, 0x6927e330, 0xc0c7735f, 0x76d32f6d, 0xa883d4ee, 0x3535d090, 0x29f4350f, 0xc1831416, 0xa2591e0b, 0x44aa80ed, 0xd5c68ccd, 0x7e2072b0),
+        SECP256K1_GE_STORAGE_CONST(0xbe0bc11b, 0x2bc639cb, 0xc28f72a8, 0xd07c21cc, 0xbc06cfa7, 0x4c2ff25e, 0x630c9740, 0x23128eab, 0x6f062fc8, 0x75148197, 0xd10375c3, 0xcc3fadb6, 0x20277e9c, 0x00579c55, 0xeddd7f95, 0xe95604db),
+        SECP256K1_GE_STORAGE_CONST(0xbe0bc11b, 0x2bc639cb, 0xc28f72a8, 0xd07c21cc, 0xbc06cfa7, 0x4c2ff25e, 0x630c9740, 0x23128eab, 0x90f9d037, 0x8aeb7e68, 0x2efc8a3c, 0x33c05249, 0xdfd88163, 0xffa863aa, 0x12228069, 0x16a9f754),
+        SECP256K1_GE_STORAGE_CONST(0xedd1fd3e, 0x327ce90c, 0xc7a35426, 0x14289aee, 0x9682003e, 0x9cf7dcc9, 0xcf2ca974, 0x3be5aa0c, 0xfdda0ad6, 0x118a5350, 0x3303ba9f, 0xd93a1b94, 0x07fdc85c, 0xc6db9aa5, 0xe906f176, 0xf7a12705),
+        SECP256K1_GE_STORAGE_CONST(0xedd1fd3e, 0x327ce90c, 0xc7a35426, 0x14289aee, 0x9682003e, 0x9cf7dcc9, 0xcf2ca974, 0x3be5aa0c, 0x0225f529, 0xee75acaf, 0xccfc4560, 0x26c5e46b, 0xf80237a3, 0x3924655a, 0x16f90e88, 0x085ed52a),
+        SECP256K1_GE_STORAGE_CONST(0xaee172d4, 0xce7c5010, 0xdb20a88f, 0x469598c1, 0xd7f7926f, 0xabb85cb5, 0x339f1403, 0x87e6b494, 0x38065980, 0x4de81b35, 0x098c7190, 0xe3380f9d, 0x95b2ed6c, 0x6c869e85, 0xc772bc5a, 0x7bc3d9d5),
+        SECP256K1_GE_STORAGE_CONST(0xaee172d4, 0xce7c5010, 0xdb20a88f, 0x469598c1, 0xd7f7926f, 0xabb85cb5, 0x339f1403, 0x87e6b494, 0xc7f9a67f, 0xb217e4ca, 0xf6738e6f, 0x1cc7f062, 0x6a4d1293, 0x9379617a, 0x388d43a4, 0x843c225a),
+        SECP256K1_GE_STORAGE_CONST(0xc28f5c28, 0xf5c28f5c, 0x28f5c28f, 0x5c28f5c2, 0x8f5c28f5, 0xc28f5c28, 0xf5c28f5b, 0x6666635a, 0x0c4da840, 0x1b2cf5be, 0x4604e6ec, 0xf92b2780, 0x063a5351, 0xe294bf65, 0xbb2f8b61, 0x00902db7),
+        SECP256K1_GE_STORAGE_CONST(0xc28f5c28, 0xf5c28f5c, 0x28f5c28f, 0x5c28f5c2, 0x8f5c28f5, 0xc28f5c28, 0xf5c28f5b, 0x6666635a, 0xf3b257bf, 0xe4d30a41, 0xb9fb1913, 0x06d4d87f, 0xf9c5acae, 0x1d6b409a, 0x44d0749d, 0xff6fce78),
+        SECP256K1_GE_STORAGE_CONST(0xecf56be6, 0x9c8fde26, 0x152832c6, 0xe043b3d5, 0xaf9a723f, 0x789854a0, 0xcb1b810d, 0xe2614ece, 0x66127ae4, 0xe4c17a75, 0x60a727e6, 0xffd2ea7f, 0xaed99088, 0xbec465c6, 0xbde56791, 0x37ed5572),
+        SECP256K1_GE_STORAGE_CONST(0xecf56be6, 0x9c8fde26, 0x152832c6, 0xe043b3d5, 0xaf9a723f, 0x789854a0, 0xcb1b810d, 0xe2614ece, 0x99ed851b, 0x1b3e858a, 0x9f58d819, 0x002d1580, 0x51266f77, 0x413b9a39, 0x421a986d, 0xc812a6bd),
+        SECP256K1_GE_STORAGE_CONST(0xba72860f, 0x10fcd142, 0x23f71e3c, 0x228deb9a, 0xc46c5ff5, 0x90b884e5, 0xcc60d51e, 0x0629d16e, 0x67999f31, 0x5a74ada3, 0x526832cf, 0x76b9fec3, 0xa348cc97, 0x33c3aa67, 0x02bd2516, 0x7814f635),
+        SECP256K1_GE_STORAGE_CONST(0xba72860f, 0x10fcd142, 0x23f71e3c, 0x228deb9a, 0xc46c5ff5, 0x90b884e5, 0xcc60d51e, 0x0629d16e, 0x986660ce, 0xa58b525c, 0xad97cd30, 0x8946013c, 0x5cb73368, 0xcc3c5598, 0xfd42dae8, 0x87eb05fa),
+        SECP256K1_GE_STORAGE_CONST(0x92ef5657, 0xdba51cc7, 0xf3e1b442, 0xa6a0916b, 0x8ce03079, 0x2ef5657d, 0xba51cc7e, 0xab2beb65, 0x782c65d2, 0x3f1e0eb2, 0x9179a994, 0xe5e8ff80, 0x5a0d50d9, 0xdeeaed90, 0xcec96ca5, 0x973e2ad3),
+        SECP256K1_GE_STORAGE_CONST(0x92ef5657, 0xdba51cc7, 0xf3e1b442, 0xa6a0916b, 0x8ce03079, 0x2ef5657d, 0xba51cc7e, 0xab2beb65, 0x87d39a2d, 0xc0e1f14d, 0x6e86566b, 0x1a17007f, 0xa5f2af26, 0x2115126f, 0x31369359, 0x68c1d15c),
+        SECP256K1_GE_STORAGE_CONST(0x9468ad22, 0xf921fc78, 0x8de3f1b0, 0x586c58eb, 0x5e6f0270, 0xe950b602, 0x7ada90d9, 0xd71ae323, 0x922a0c6a, 0x9ccc31d9, 0xc3bf87fd, 0x88381739, 0x35fe393f, 0xa64dfdec, 0x29f2846d, 0x12918d86),
+        SECP256K1_GE_STORAGE_CONST(0x9468ad22, 0xf921fc78, 0x8de3f1b0, 0x586c58eb, 0x5e6f0270, 0xe950b602, 0x7ada90d9, 0xd71ae323, 0x6dd5f395, 0x6333ce26, 0x3c407802, 0x77c7e8c6, 0xca01c6c0, 0x59b20213, 0xd60d7b91, 0xed6e6ea9),
+        SECP256K1_GE_STORAGE_CONST(0x76ddc7f5, 0xe029e59e, 0x22b0e54f, 0xa811db94, 0x5a209c4f, 0x5e912ca2, 0x8b4da6a7, 0x4c1e00a2, 0x1e8f516c, 0x91c20437, 0x50f6e24e, 0x8c2cf202, 0xacf68291, 0xbf8b66eb, 0xf7335b62, 0xec2c88fe),
+        SECP256K1_GE_STORAGE_CONST(0x76ddc7f5, 0xe029e59e, 0x22b0e54f, 0xa811db94, 0x5a209c4f, 0x5e912ca2, 0x8b4da6a7, 0x4c1e00a2, 0xe170ae93, 0x6e3dfbc8, 0xaf091db1, 0x73d30dfd, 0x53097d6e, 0x40749914, 0x08cca49c, 0x13d37331),
+        SECP256K1_GE_STORAGE_CONST(0xf75763bc, 0x2907e79b, 0x125e33c3, 0x9a027f48, 0x0f8c6409, 0x2153432f, 0x967bc2b1, 0x1d1f5cf0, 0xb4a8edc6, 0x36391b39, 0x9bc219c0, 0x3d033128, 0xdbcd463e, 0xd2506394, 0x061b87a5, 0x9e510235),
+        SECP256K1_GE_STORAGE_CONST(0xf75763bc, 0x2907e79b, 0x125e33c3, 0x9a027f48, 0x0f8c6409, 0x2153432f, 0x967bc2b1, 0x1d1f5cf0, 0x4b571239, 0xc9c6e4c6, 0x643de63f, 0xc2fcced7, 0x2432b9c1, 0x2daf9c6b, 0xf9e47859, 0x61aef9fa),
+    };
+
+    secp256k1_ge ge;
+    secp256k1_fe fe;
+    secp256k1_ge_storage ges;
+    int i, s;
+    for (i = 1; i <= 16; i++) {
+        secp256k1_fe_set_int(&fe, i);
+
+        for (s = 0; s < 2; s++) {
+            if (s) {
+                secp256k1_fe_negate(&fe, &fe, 1);
+                secp256k1_fe_normalize(&fe);
+            }
+            shallue_van_de_woestijne(&ge, &fe);
+            secp256k1_ge_to_storage(&ges, &ge);
+
+            CHECK(memcmp(&ges, &results[i * 2 + s - 2], sizeof(secp256k1_ge_storage)) == 0);
+        }
+    }
+}
+
+void test_generator_generate(void) {
+    static const secp256k1_ge_storage results[32] = {
+        SECP256K1_GE_STORAGE_CONST(0x806cd8ed, 0xd6c153e3, 0x4aa9b9a0, 0x8755c4be, 0x4718b1ef, 0xb26cb93f, 0xfdd99e1b, 0x21f2af8e, 0xc7062208, 0xcc649a03, 0x1bdc1a33, 0x9d01f115, 0x4bcd0dca, 0xfe0b875d, 0x62f35f73, 0x28673006),
+        SECP256K1_GE_STORAGE_CONST(0xd91b15ec, 0x47a811f4, 0xaa189561, 0xd13f5c4d, 0x4e81f10d, 0xc7dc551f, 0x4fea9b84, 0x610314c4, 0x9b0ada1e, 0xb38efd67, 0x8bff0b6c, 0x7d7315f7, 0xb49b8cc5, 0xa679fad4, 0xc94f9dc6, 0x9da66382),
+        SECP256K1_GE_STORAGE_CONST(0x11c00de6, 0xf885035e, 0x76051430, 0xa3c38b2a, 0x5f86ab8c, 0xf66dae58, 0x04ea7307, 0x348b19bf, 0xe0858ae7, 0x61dcb1ba, 0xff247e37, 0xd38fcd88, 0xf3bd7911, 0xaa4ed6e0, 0x28d792dd, 0x3ee1ac09),
+        SECP256K1_GE_STORAGE_CONST(0x986b99eb, 0x3130e7f0, 0xe779f674, 0xb85cb514, 0x46a676bf, 0xb1dfb603, 0x4c4bb639, 0x7c406210, 0xdf900609, 0x8b3ef1e0, 0x30e32fb0, 0xd97a4329, 0xff98aed0, 0xcd278c3f, 0xe6078467, 0xfbd12f35),
+        SECP256K1_GE_STORAGE_CONST(0xae528146, 0x03fdf91e, 0xc592977e, 0x12461dc7, 0xb9e038f8, 0x048dcb62, 0xea264756, 0xd459ae42, 0x80ef658d, 0x92becb84, 0xdba8e4f9, 0x560d7a72, 0xbaf4c393, 0xfbcf6007, 0x11039f1c, 0x224faaad),
+        SECP256K1_GE_STORAGE_CONST(0x00df3d91, 0x35975eee, 0x91fab903, 0xe3128e4a, 0xca071dde, 0x270814e5, 0xcbda69ec, 0xcad58f46, 0x11b590aa, 0x92d89969, 0x2dbd932f, 0x08013b8b, 0x45afabc6, 0x43677db2, 0x143e0c0f, 0x5865fb03),
+        SECP256K1_GE_STORAGE_CONST(0x1168155b, 0x987e9bc8, 0x84c5f3f4, 0x92ebf784, 0xcc8c6735, 0x39d8e5e8, 0xa967115a, 0x2949da9b, 0x0858a470, 0xf403ca97, 0xb1827f6f, 0x544c2c67, 0x08f6cb83, 0xc510c317, 0x96c981ed, 0xb9f61780),
+        SECP256K1_GE_STORAGE_CONST(0xe8d7c0cf, 0x2bb4194c, 0x97bf2a36, 0xbd115ba0, 0x81a9afe8, 0x7663fa3c, 0x9c3cd253, 0x79fe2571, 0x2028ad04, 0xefa00119, 0x5a25d598, 0x67e79502, 0x49de7c61, 0x4751cd9d, 0x4fb317f6, 0xf76f1110),
+        SECP256K1_GE_STORAGE_CONST(0x9532c491, 0xa64851dd, 0xcd0d3e5a, 0x93e17267, 0xa10aca95, 0xa23781aa, 0x5087f340, 0xc45fecc3, 0xb691ddc2, 0x3143a7b6, 0x09969302, 0x258affb8, 0x5bbf8666, 0xe1192319, 0xeb174d88, 0x308bd57a),
+        SECP256K1_GE_STORAGE_CONST(0x6b20b6e2, 0x1ba6cc44, 0x3f2c3a0c, 0x5283ba44, 0xbee43a0a, 0x2799a6cf, 0xbecc0f8a, 0xf8c583ac, 0xf7021e76, 0xd51291a6, 0xf9396215, 0x686f25aa, 0xbec36282, 0x5e11eeea, 0x6e51a6e6, 0xd7d7c006),
+        SECP256K1_GE_STORAGE_CONST(0xde27e6ff, 0x219b3ab1, 0x2b0a9e4e, 0x51fc6092, 0x96e55af6, 0xc6f717d6, 0x12cd6cce, 0x65d6c8f2, 0x48166884, 0x4dc13fd2, 0xed7a7d81, 0x66a0839a, 0x8a960863, 0xfe0001c1, 0x35d206fd, 0x63b87c09),
+        SECP256K1_GE_STORAGE_CONST(0x79a96fb8, 0xd88a08d3, 0x055d38d1, 0x3346b0d4, 0x47d838ca, 0xfcc8fa40, 0x6d3a7157, 0xef84e7e3, 0x6bab9c45, 0x2871b51d, 0xb0df2369, 0xe7860e01, 0x2e37ffea, 0x6689fd1a, 0x9c6fe9cf, 0xb940acea),
+        SECP256K1_GE_STORAGE_CONST(0x06c4d4cb, 0xd32c0ddb, 0x67e988c6, 0x2bdbe6ad, 0xa39b80cc, 0x61afb347, 0x234abe27, 0xa689618c, 0x5b355949, 0xf904fe08, 0x569b2313, 0xe8f19f8d, 0xc5b79e27, 0x70da0832, 0x5fb7a229, 0x238ca6b6),
+        SECP256K1_GE_STORAGE_CONST(0x7027e566, 0x3e727c28, 0x42aa14e5, 0x52c2d2ec, 0x1d8beaa9, 0x8a22ceab, 0x15ccafc3, 0xb4f06249, 0x9b3dffbc, 0xdbd5e045, 0x6931fd03, 0x8b1c6a9b, 0x4c168c6d, 0xa6553897, 0xfe11ce49, 0xac728139),
+        SECP256K1_GE_STORAGE_CONST(0xee3520c3, 0x9f2b954d, 0xf8e15547, 0xdaeb6cc8, 0x04c8f3b0, 0x9301f53e, 0xe0c11ea1, 0xeace539d, 0x244ff873, 0x7e060c98, 0xe843c353, 0xcd35d2e4, 0x3cd8b082, 0xcffbc9ae, 0x81eafa70, 0x332f9748),
+        SECP256K1_GE_STORAGE_CONST(0xdaecd756, 0xf5b706a4, 0xc14e1095, 0x3e2f70df, 0xa81276e7, 0x71806b89, 0x4d8a5502, 0xa0ef4998, 0xbac906c0, 0x948b1d48, 0xe023f439, 0xfd3770b8, 0x837f60cc, 0x40552a51, 0x433d0b79, 0x6610da27),
+        SECP256K1_GE_STORAGE_CONST(0x55e1ca28, 0x750fe2d0, 0x57f7449b, 0x3f49d999, 0x3b9616dd, 0x5387bc2e, 0x6e6698f8, 0xc4ea49f4, 0xe339e0e9, 0xa4c7fa99, 0xd063e062, 0x6582bce2, 0x33c6b1ee, 0x17a5b47f, 0x6d43ecf8, 0x98b40120),
+        SECP256K1_GE_STORAGE_CONST(0xdd82cac2, 0x9e0e0135, 0x4964d3bc, 0x27469233, 0xf13bbd5e, 0xd7aff24b, 0x4902fca8, 0x17294b12, 0x561ab1d6, 0xcd9bcb6e, 0x805585cf, 0x3df8714c, 0x1bfa6304, 0x5efbf122, 0x1a3d8fd9, 0x3827764a),
+        SECP256K1_GE_STORAGE_CONST(0xda5cbfb7, 0x3522e9c7, 0xcb594436, 0x83677038, 0x0eaa64a9, 0x2eca3888, 0x0fe4c9d6, 0xdeb22dbf, 0x4f46de68, 0x0447c780, 0xc54a314b, 0x5389a926, 0xbba8910b, 0x869fc6cd, 0x42ee82e8, 0x5895e42a),
+        SECP256K1_GE_STORAGE_CONST(0x4e09830e, 0xc8894c58, 0x4e6278de, 0x167a96b0, 0x20d60463, 0xee48f788, 0x4974d66e, 0x871e35e9, 0x21259c4d, 0x332ca932, 0x2e187df9, 0xe7afbc23, 0x9d171ebc, 0x7d9e2560, 0x503f50b1, 0x9fe45834),
+        SECP256K1_GE_STORAGE_CONST(0xabfff6ca, 0x41dcfd17, 0x03cae629, 0x9d127971, 0xf19ee000, 0x2db332e6, 0x5cc209a3, 0xc21b8f54, 0x65991d60, 0xee54f5cc, 0xddf7a732, 0xa76b0303, 0xb9f519a6, 0x22ea0390, 0x8af23ffa, 0x35ae6632),
+        SECP256K1_GE_STORAGE_CONST(0xc6c9b92c, 0x91e045a5, 0xa1913277, 0x44d6fce2, 0x11b12c7c, 0x9b3112d6, 0xc61e14a6, 0xd6b1ae12, 0x04ab0396, 0xebdc4c6a, 0xc213cc3e, 0x077a2e80, 0xb4ba7b2b, 0x33907d56, 0x2c98ccf7, 0xb82a2e9f),
+        SECP256K1_GE_STORAGE_CONST(0x66f6e6d9, 0xc4bb9a5f, 0x99085781, 0x83cb9362, 0x2ea437d8, 0xccd31969, 0xffadca3a, 0xff1d3935, 0x50a5b06e, 0x39e039d7, 0x1dfb2723, 0x18db74e5, 0x5af64da1, 0xdfc34586, 0x6aac3bd0, 0x5792a890),
+        SECP256K1_GE_STORAGE_CONST(0x58ded03c, 0x98e1a890, 0x63fc7793, 0xe3ecd896, 0x235e75c9, 0x82e7008f, 0xddbf3ca8, 0x5b7e9ecb, 0x34594776, 0x58ab6821, 0xaf43a453, 0xa946fda9, 0x13d24999, 0xccf22df8, 0xd291ef59, 0xb08975c0),
+        SECP256K1_GE_STORAGE_CONST(0x74557864, 0x4f2b0486, 0xd5beea7c, 0x2d258ccb, 0x78a870e1, 0x848982d8, 0xed3f91a4, 0x9db83a36, 0xd84e940e, 0x1d33c28a, 0x62398ec8, 0xc493aee7, 0x7c2ba722, 0x42dee7ae, 0x3c35c256, 0xad00cf42),
+        SECP256K1_GE_STORAGE_CONST(0x7fc7963a, 0x16abc8fb, 0x5d61eb61, 0x0fc50a68, 0x754470d2, 0xf43df3be, 0x52228f66, 0x522fe61b, 0x499f9e7f, 0x462c6545, 0x29687af4, 0x9f7c732d, 0x48801ce5, 0x21acd546, 0xc6fb903c, 0x7c265032),
+        SECP256K1_GE_STORAGE_CONST(0xb2f6257c, 0xc58df82f, 0xb9ba4f36, 0x7ededf03, 0xf8ea10f3, 0x104d7ae6, 0x233b7ac4, 0x725e11de, 0x9c7a32df, 0x4842f33d, 0xaad84f0b, 0x62e88b40, 0x46ddcbde, 0xbbeec6f8, 0x93bfde27, 0x0561dc73),
+        SECP256K1_GE_STORAGE_CONST(0xe2cdfd27, 0x8a8e22be, 0xabf08b79, 0x1bc6ae38, 0x41d22a9a, 0x9472e266, 0x1a7c6e83, 0xa2f74725, 0x0e26c103, 0xe0dd93b2, 0x3724f3b7, 0x8bb7366e, 0x2c245768, 0xd64f3283, 0xd8316e8a, 0x1383b977),
+        SECP256K1_GE_STORAGE_CONST(0x757c13e7, 0xe866017e, 0xe6af61d7, 0x161d208a, 0xc438f712, 0x242fcd23, 0x63a10e59, 0xd67e41fb, 0xb550c6a9, 0x4ddb15f3, 0xfeea4bfe, 0xd2faa19f, 0x2aa2fbd3, 0x0c6ae785, 0xe357f365, 0xb30d12e0),
+        SECP256K1_GE_STORAGE_CONST(0x528d525e, 0xac30095b, 0x5e5f83ca, 0x4d3dea63, 0xeb608f2d, 0x18dd25a7, 0x2529c8e5, 0x1ae5f9f1, 0xfde2860b, 0x492a4106, 0x9f356c05, 0x3ebc045e, 0x4ad08b79, 0x3e264935, 0xf25785a9, 0x8690b5ee),
+        SECP256K1_GE_STORAGE_CONST(0x150df593, 0x5b6956a0, 0x0cfed843, 0xb9d6ffce, 0x4f790022, 0xea18730f, 0xc495111d, 0x91568e55, 0x6700a2ca, 0x9ff4ed32, 0xc1697312, 0x4eb51ce3, 0x5656344b, 0x65a1e3d5, 0xd6c1f7ce, 0x29233f82),
+        SECP256K1_GE_STORAGE_CONST(0x38e02eaf, 0x2c8774fd, 0x58b8b373, 0x732457f1, 0x16dbe53b, 0xea5683d9, 0xada20dd7, 0x14ce20a6, 0x6ac5362e, 0xbb425416, 0x8250f43f, 0xa4ee2b63, 0x0406324f, 0x1c876d60, 0xebe5be2c, 0x6eb1515b),
+    };
+    secp256k1_generator gen;
+    secp256k1_ge ge;
+    secp256k1_ge_storage ges;
+    int i;
+    unsigned char v[32];
+    unsigned char s[32] = {0};
+    secp256k1_scalar sc;
+    secp256k1_scalar_set_b32(&sc, s, NULL);
+    for (i = 1; i <= 32; i++) {
+        memset(v, 0, 31);
+        v[31] = i;
+        CHECK(secp256k1_generator_generate_blinded(ctx, &gen, v, s));
+        secp256k1_generator_load(&ge, &gen);
+        secp256k1_ge_to_storage(&ges, &ge);
+        CHECK(memcmp(&ges, &results[i - 1], sizeof(secp256k1_ge_storage)) == 0);
+        CHECK(secp256k1_generator_generate(ctx, &gen, v));
+        secp256k1_generator_load(&ge, &gen);
+        secp256k1_ge_to_storage(&ges, &ge);
+        CHECK(memcmp(&ges, &results[i - 1], sizeof(secp256k1_ge_storage)) == 0);
+    }
+
+    /* There is no range restriction on the value, but the blinder must be a
+     * valid scalar. Check that an invalid blinder causes the call to fail
+     * but not crash. */
+    memset(v, 0xff, 32);
+    CHECK(secp256k1_generator_generate(ctx, &gen, v));
+    memset(s, 0xff, 32);
+    CHECK(!secp256k1_generator_generate_blinded(ctx, &gen, v, s));
+}
+
+void test_generator_fixed_vector(void) {
+    const unsigned char two_g[33] = {
+        0x0b,
+        0xc6, 0x04, 0x7f, 0x94, 0x41, 0xed, 0x7d, 0x6d, 0x30, 0x45, 0x40, 0x6e, 0x95, 0xc0, 0x7c, 0xd8,
+        0x5c, 0x77, 0x8e, 0x4b, 0x8c, 0xef, 0x3c, 0xa7, 0xab, 0xac, 0x09, 0xb9, 0x5c, 0x70, 0x9e, 0xe5
+    };
+    unsigned char result[33];
+    secp256k1_generator parse;
+
+    CHECK(secp256k1_generator_parse(ctx, &parse, two_g));
+    CHECK(secp256k1_generator_serialize(ctx, result, &parse));
+    CHECK(memcmp(two_g, result, 33) == 0);
+
+    result[0] = 0x0a;
+    CHECK(secp256k1_generator_parse(ctx, &parse, result));
+    result[0] = 0x08;
+    CHECK(!secp256k1_generator_parse(ctx, &parse, result));
+}
+
+void run_generator_tests(void) {
+    test_shallue_van_de_woestijne();
+    test_generator_fixed_vector();
+    test_generator_api();
+    test_generator_generate();
+}
+
+#endif

src/modules/musig/Makefile.am.include

@@ -0,0 +1,16 @@
+include_HEADERS += include/secp256k1_musig.h
+noinst_HEADERS += src/modules/musig/main_impl.h
+noinst_HEADERS += src/modules/musig/tests_impl.h
+
+noinst_PROGRAMS += example_musig
+example_musig_SOURCES = src/modules/musig/example.c
+example_musig_CPPFLAGS = -DSECP256K1_BUILD -I$(top_srcdir)/include $(SECP_INCLUDES)
+if !ENABLE_COVERAGE
+example_musig_CPPFLAGS += -DVERIFY
+endif
+example_musig_LDADD = libsecp256k1.la $(SECP_LIBS)
+example_musig_LDFLAGS = -static
+
+if USE_TESTS
+TESTS += example_musig
+endif

src/modules/musig/example.c

@@ -0,0 +1,165 @@
+/**********************************************************************
+ * Copyright (c) 2018 Jonas Nick                                      *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+/**
+ * This file demonstrates how to use the MuSig module to create a multisignature.
+ * Additionally, see the documentation in include/secp256k1_musig.h.
+ */
+
+#include <stdio.h>
+#include <assert.h>
+#include <secp256k1.h>
+#include <secp256k1_schnorrsig.h>
+#include <secp256k1_musig.h>
+
+ /* Number of public keys involved in creating the aggregate signature */
+#define N_SIGNERS 3
+ /* Create a key pair and store it in seckey and pubkey */
+int create_key(const secp256k1_context* ctx, unsigned char* seckey, secp256k1_pubkey* pubkey) {
+    int ret;
+    FILE *frand = fopen("/dev/urandom", "r");
+    if (frand == NULL) {
+        return 0;
+    }
+    do {
+         if(!fread(seckey, 32, 1, frand)) {
+             fclose(frand);
+             return 0;
+         }
+    /* The probability that this not a valid secret key is approximately 2^-128 */
+    } while (!secp256k1_ec_seckey_verify(ctx, seckey));
+    fclose(frand);
+    ret = secp256k1_ec_pubkey_create(ctx, pubkey, seckey);
+    return ret;
+}
+
+/* Sign a message hash with the given key pairs and store the result in sig */
+int sign(const secp256k1_context* ctx, unsigned char seckeys[][32], const secp256k1_pubkey* pubkeys, const unsigned char* msg32, secp256k1_schnorrsig *sig) {
+    secp256k1_musig_session musig_session[N_SIGNERS];
+    unsigned char nonce_commitment[N_SIGNERS][32];
+    const unsigned char *nonce_commitment_ptr[N_SIGNERS];
+    secp256k1_musig_session_signer_data signer_data[N_SIGNERS][N_SIGNERS];
+    secp256k1_pubkey nonce[N_SIGNERS];
+    int i, j;
+    secp256k1_musig_partial_signature partial_sig[N_SIGNERS];
+
+    for (i = 0; i < N_SIGNERS; i++) {
+        FILE *frand;
+        unsigned char session_id32[32];
+        unsigned char pk_hash[32];
+        secp256k1_pubkey combined_pk;
+
+        /* Create combined pubkey and initialize signer data */
+        if (!secp256k1_musig_pubkey_combine(ctx, NULL, &combined_pk, pk_hash, pubkeys, N_SIGNERS)) {
+            return 0;
+        }
+        /* Create random session ID. It is absolutely necessary that the session ID
+         * is unique for every call of secp256k1_musig_session_initialize. Otherwise
+         * it's trivial for an attacker to extract the secret key! */
+        frand = fopen("/dev/urandom", "r");
+        if(frand == NULL) {
+            return 0;
+        }
+        if (!fread(session_id32, 32, 1, frand)) {
+            fclose(frand);
+            return 0;
+        }
+        fclose(frand);
+        /* Initialize session */
+        if (!secp256k1_musig_session_initialize(ctx, &musig_session[i], signer_data[i], nonce_commitment[i], session_id32, msg32, &combined_pk, pk_hash, N_SIGNERS, i, seckeys[i])) {
+            return 0;
+        }
+        nonce_commitment_ptr[i] = &nonce_commitment[i][0];
+    }
+    /* Communication round 1: Exchange nonce commitments */
+    for (i = 0; i < N_SIGNERS; i++) {
+        /* Set nonce commitments in the signer data and get the own public nonce */
+        if (!secp256k1_musig_session_get_public_nonce(ctx, &musig_session[i], signer_data[i], &nonce[i], nonce_commitment_ptr, N_SIGNERS)) {
+            return 0;
+        }
+    }
+    /* Communication round 2: Exchange nonces */
+    for (i = 0; i < N_SIGNERS; i++) {
+        for (j = 0; j < N_SIGNERS; j++) {
+            if (!secp256k1_musig_set_nonce(ctx, &signer_data[i][j], &nonce[j])) {
+                /* Signer j's nonce does not match the nonce commitment. In this case
+                 * abort the protocol. If you make another attempt at finishing the
+                 * protocol, create a new session (with a fresh session ID!). */
+                return 0;
+            }
+        }
+        if (!secp256k1_musig_session_combine_nonces(ctx, &musig_session[i], signer_data[i], N_SIGNERS, NULL, NULL)) {
+            return 0;
+        }
+    }
+    for (i = 0; i < N_SIGNERS; i++) {
+        if (!secp256k1_musig_partial_sign(ctx, &musig_session[i], &partial_sig[i])) {
+            return 0;
+        }
+    }
+    /* Communication round 3: Exchange partial signatures */
+    for (i = 0; i < N_SIGNERS; i++) {
+        for (j = 0; j < N_SIGNERS; j++) {
+            /* To check whether signing was successful, it suffices to either verify
+             * the the combined signature with the combined public key using
+             * secp256k1_schnorrsig_verify, or verify all partial signatures of all
+             * signers individually. Verifying the combined signature is cheaper but
+             * verifying the individual partial signatures has the advantage that it
+             * can be used to determine which of the partial signatures are invalid
+             * (if any), i.e., which of the partial signatures cause the combined
+             * signature to be invalid and thus the protocol run to fail. It's also
+             * fine to first verify the combined sig, and only verify the individual
+             * sigs if it does not work.
+             */
+            if (!secp256k1_musig_partial_sig_verify(ctx, &musig_session[i], &signer_data[i][j], &partial_sig[j], &pubkeys[j])) {
+                return 0;
+            }
+        }
+    }
+    return secp256k1_musig_partial_sig_combine(ctx, &musig_session[0], sig, partial_sig, N_SIGNERS);
+}
+
+ int main(void) {
+    secp256k1_context* ctx;
+    int i;
+    unsigned char seckeys[N_SIGNERS][32];
+    secp256k1_pubkey pubkeys[N_SIGNERS];
+    secp256k1_pubkey combined_pk;
+    unsigned char msg[32] = "this_could_be_the_hash_of_a_msg!";
+    secp256k1_schnorrsig sig;
+
+    /* Create a context for signing and verification */
+    ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+    printf("Creating key pairs......");
+    for (i = 0; i < N_SIGNERS; i++) {
+        if (!create_key(ctx, seckeys[i], &pubkeys[i])) {
+            printf("FAILED\n");
+            return 1;
+        }
+    }
+    printf("ok\n");
+    printf("Combining public keys...");
+    if (!secp256k1_musig_pubkey_combine(ctx, NULL, &combined_pk, NULL, pubkeys, N_SIGNERS)) {
+        printf("FAILED\n");
+        return 1;
+    }
+    printf("ok\n");
+    printf("Signing message.........");
+    if (!sign(ctx, seckeys, pubkeys, msg, &sig)) {
+        printf("FAILED\n");
+        return 1;
+    }
+    printf("ok\n");
+    printf("Verifying signature.....");
+    if (!secp256k1_schnorrsig_verify(ctx, &sig, msg, &combined_pk)) {
+        printf("FAILED\n");
+        return 1;
+    }
+    printf("ok\n");
+    secp256k1_context_destroy(ctx);
+    return 0;
+}
+

src/modules/musig/main_impl.h

@@ -0,0 +1,629 @@
+/**********************************************************************
+ * Copyright (c) 2018 Andrew Poelstra, Jonas Nick                     *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_MODULE_MUSIG_MAIN_
+#define _SECP256K1_MODULE_MUSIG_MAIN_
+
+#include "include/secp256k1.h"
+#include "include/secp256k1_musig.h"
+#include "hash.h"
+
+/* Computes ell = SHA256(pk[0], ..., pk[np-1]) */
+static int secp256k1_musig_compute_ell(const secp256k1_context *ctx, unsigned char *ell, const secp256k1_pubkey *pk, size_t np) {
+    secp256k1_sha256 sha;
+    size_t i;
+
+    secp256k1_sha256_initialize(&sha);
+    for (i = 0; i < np; i++) {
+        unsigned char ser[33];
+        size_t serlen = sizeof(ser);
+        if (!secp256k1_ec_pubkey_serialize(ctx, ser, &serlen, &pk[i], SECP256K1_EC_COMPRESSED)) {
+            return 0;
+        }
+        secp256k1_sha256_write(&sha, ser, serlen);
+    }
+    secp256k1_sha256_finalize(&sha, ell);
+    return 1;
+}
+
+/* Initializes SHA256 with fixed midstate. This midstate was computed by applying
+ * SHA256 to SHA256("MuSig coefficient")||SHA256("MuSig coefficient"). */
+static void secp256k1_musig_sha256_init_tagged(secp256k1_sha256 *sha) {
+    secp256k1_sha256_initialize(sha);
+
+    sha->s[0] = 0x0fd0690cul;
+    sha->s[1] = 0xfefeae97ul;
+    sha->s[2] = 0x996eac7ful;
+    sha->s[3] = 0x5c30d864ul;
+    sha->s[4] = 0x8c4a0573ul;
+    sha->s[5] = 0xaca1a22ful;
+    sha->s[6] = 0x6f43b801ul;
+    sha->s[7] = 0x85ce27cdul;
+    sha->bytes = 64;
+}
+
+/* Compute r = SHA256(ell, idx). The four bytes of idx are serialized least significant byte first. */
+static void secp256k1_musig_coefficient(secp256k1_scalar *r, const unsigned char *ell, uint32_t idx) {
+    secp256k1_sha256 sha;
+    unsigned char buf[32];
+    size_t i;
+
+    secp256k1_musig_sha256_init_tagged(&sha);
+    secp256k1_sha256_write(&sha, ell, 32);
+    /* We're hashing the index of the signer instead of its public key as specified
+     * in the MuSig paper. This reduces the total amount of data that needs to be
+     * hashed.
+     * Additionally, it prevents creating identical musig_coefficients for identical
+     * public keys. A participant Bob could choose his public key to be the same as
+     * Alice's, then replay Alice's messages (nonce and partial signature) to create
+     * a valid partial signature. This is not a problem for MuSig per se, but could
+     * result in subtle issues with protocols building on threshold signatures.
+     * With the assumption that public keys are unique, hashing the index is
+     * equivalent to hashing the public key. Because the public key can be
+     * identified by the index given the ordered list of public keys (included in
+     * ell), the index is just a different encoding of the public key.*/
+    for (i = 0; i < sizeof(uint32_t); i++) {
+        unsigned char c = idx;
+        secp256k1_sha256_write(&sha, &c, 1);
+        idx >>= 8;
+    }
+    secp256k1_sha256_finalize(&sha, buf);
+    secp256k1_scalar_set_b32(r, buf, NULL);
+}
+
+typedef struct {
+    const secp256k1_context *ctx;
+    unsigned char ell[32];
+    const secp256k1_pubkey *pks;
+} secp256k1_musig_pubkey_combine_ecmult_data;
+
+/* Callback for batch EC multiplication to compute ell_0*P0 + ell_1*P1 + ...  */
+static int secp256k1_musig_pubkey_combine_callback(secp256k1_scalar *sc, secp256k1_ge *pt, size_t idx, void *data) {
+    secp256k1_musig_pubkey_combine_ecmult_data *ctx = (secp256k1_musig_pubkey_combine_ecmult_data *) data;
+    secp256k1_musig_coefficient(sc, ctx->ell, idx);
+    return secp256k1_pubkey_load(ctx->ctx, pt, &ctx->pks[idx]);
+}
+
+
+static void secp256k1_musig_signers_init(secp256k1_musig_session_signer_data *signers, uint32_t n_signers) {
+    uint32_t i;
+    for (i = 0; i < n_signers; i++) {
+        memset(&signers[i], 0, sizeof(signers[i]));
+        signers[i].index = i;
+        signers[i].present = 0;
+    }
+}
+
+int secp256k1_musig_pubkey_combine(const secp256k1_context* ctx, secp256k1_scratch_space *scratch, secp256k1_pubkey *combined_pk, unsigned char *pk_hash32, const secp256k1_pubkey *pubkeys, size_t n_pubkeys) {
+    secp256k1_musig_pubkey_combine_ecmult_data ecmult_data;
+    secp256k1_gej pkj;
+    secp256k1_ge pkp;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(combined_pk != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(pubkeys != NULL);
+    ARG_CHECK(n_pubkeys > 0);
+
+    ecmult_data.ctx = ctx;
+    ecmult_data.pks = pubkeys;
+    if (!secp256k1_musig_compute_ell(ctx, ecmult_data.ell, pubkeys, n_pubkeys)) {
+        return 0;
+    }
+    if (!secp256k1_ecmult_multi_var(&ctx->ecmult_ctx, scratch, &pkj, NULL, secp256k1_musig_pubkey_combine_callback, (void *) &ecmult_data, n_pubkeys)) {
+        return 0;
+    }
+    secp256k1_ge_set_gej(&pkp, &pkj);
+    secp256k1_pubkey_save(combined_pk, &pkp);
+
+    if (pk_hash32 != NULL) {
+        memcpy(pk_hash32, ecmult_data.ell, 32);
+    }
+    return 1;
+}
+
+int secp256k1_musig_session_initialize(const secp256k1_context* ctx, secp256k1_musig_session *session, secp256k1_musig_session_signer_data *signers, unsigned char *nonce_commitment32, const unsigned char *session_id32, const unsigned char *msg32, const secp256k1_pubkey *combined_pk, const unsigned char *pk_hash32, size_t n_signers, size_t my_index, const unsigned char *seckey) {
+    unsigned char combined_ser[33];
+    size_t combined_ser_size = sizeof(combined_ser);
+    int overflow;
+    secp256k1_scalar secret;
+    secp256k1_scalar mu;
+    secp256k1_sha256 sha;
+    secp256k1_gej rj;
+    secp256k1_ge rp;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(signers != NULL);
+    ARG_CHECK(nonce_commitment32 != NULL);
+    ARG_CHECK(session_id32 != NULL);
+    ARG_CHECK(combined_pk != NULL);
+    ARG_CHECK(pk_hash32 != NULL);
+    ARG_CHECK(seckey != NULL);
+
+    memset(session, 0, sizeof(*session));
+
+    if (msg32 != NULL) {
+        memcpy(session->msg, msg32, 32);
+        session->msg_is_set = 1;
+    } else {
+        session->msg_is_set = 0;
+    }
+    memcpy(&session->combined_pk, combined_pk, sizeof(*combined_pk));
+    memcpy(session->pk_hash, pk_hash32, 32);
+    session->nonce_is_set = 0;
+    session->has_secret_data = 1;
+    if (n_signers == 0 || my_index >= n_signers) {
+        return 0;
+    }
+    if (n_signers > UINT32_MAX) {
+        return 0;
+    }
+    session->n_signers = (uint32_t) n_signers;
+    secp256k1_musig_signers_init(signers, session->n_signers);
+    session->nonce_commitments_hash_is_set = 0;
+
+    /* Compute secret key */
+    secp256k1_scalar_set_b32(&secret, seckey, &overflow);
+    if (overflow) {
+        secp256k1_scalar_clear(&secret);
+        return 0;
+    }
+    secp256k1_musig_coefficient(&mu, pk_hash32, (uint32_t) my_index);
+    secp256k1_scalar_mul(&secret, &secret, &mu);
+    secp256k1_scalar_get_b32(session->seckey, &secret);
+
+    /* Compute secret nonce */
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, session_id32, 32);
+    if (session->msg_is_set) {
+        secp256k1_sha256_write(&sha, msg32, 32);
+    }
+    secp256k1_ec_pubkey_serialize(ctx, combined_ser, &combined_ser_size, combined_pk, SECP256K1_EC_COMPRESSED);
+    secp256k1_sha256_write(&sha, combined_ser, combined_ser_size);
+    secp256k1_sha256_write(&sha, seckey, 32);
+    secp256k1_sha256_finalize(&sha, session->secnonce);
+    secp256k1_scalar_set_b32(&secret, session->secnonce, &overflow);
+    if (overflow) {
+        secp256k1_scalar_clear(&secret);
+        return 0;
+    }
+
+    /* Compute public nonce and commitment */
+    secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &rj, &secret);
+    secp256k1_ge_set_gej(&rp, &rj);
+    secp256k1_pubkey_save(&session->nonce, &rp);
+
+    if (nonce_commitment32 != NULL) {
+        unsigned char commit[33];
+        size_t commit_size = sizeof(commit);
+        secp256k1_sha256_initialize(&sha);
+        secp256k1_ec_pubkey_serialize(ctx, commit, &commit_size, &session->nonce, SECP256K1_EC_COMPRESSED);
+        secp256k1_sha256_write(&sha, commit, commit_size);
+        secp256k1_sha256_finalize(&sha, nonce_commitment32);
+    }
+
+    secp256k1_scalar_clear(&secret);
+    return 1;
+}
+
+int secp256k1_musig_session_get_public_nonce(const secp256k1_context* ctx, secp256k1_musig_session *session, secp256k1_musig_session_signer_data *signers, secp256k1_pubkey *nonce, const unsigned char *const *commitments, size_t n_commitments) {
+    secp256k1_sha256 sha;
+    unsigned char nonce_commitments_hash[32];
+    size_t i;
+    (void) ctx;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(signers != NULL);
+    ARG_CHECK(nonce != NULL);
+    ARG_CHECK(commitments != NULL);
+
+    if (!session->has_secret_data || n_commitments != session->n_signers) {
+        return 0;
+    }
+    for (i = 0; i < n_commitments; i++) {
+        ARG_CHECK(commitments[i] != NULL);
+    }
+
+    secp256k1_sha256_initialize(&sha);
+    for (i = 0; i < n_commitments; i++) {
+        memcpy(signers[i].nonce_commitment, commitments[i], 32);
+        secp256k1_sha256_write(&sha, commitments[i], 32);
+    }
+    secp256k1_sha256_finalize(&sha, nonce_commitments_hash);
+    if (session->nonce_commitments_hash_is_set
+            && memcmp(session->nonce_commitments_hash, nonce_commitments_hash, 32) != 0) {
+        /* Abort if get_public_nonce has been called before with a different array of
+         * commitments. */
+        return 0;
+    }
+    memcpy(session->nonce_commitments_hash, nonce_commitments_hash, 32);
+    session->nonce_commitments_hash_is_set = 1;
+    memcpy(nonce, &session->nonce, sizeof(*nonce));
+    return 1;
+}
+
+int secp256k1_musig_session_initialize_verifier(const secp256k1_context* ctx, secp256k1_musig_session *session, secp256k1_musig_session_signer_data *signers, const unsigned char *msg32, const secp256k1_pubkey *combined_pk, const unsigned char *pk_hash32, const unsigned char *const *commitments, size_t n_signers) {
+    size_t i;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(signers != NULL);
+    ARG_CHECK(combined_pk != NULL);
+    ARG_CHECK(pk_hash32 != NULL);
+    ARG_CHECK(commitments != NULL);
+    /* Check n_signers before checking commitments to allow testing the case where
+     * n_signers is big without allocating the space. */
+    if (n_signers > UINT32_MAX) {
+        return 0;
+    }
+    for (i = 0; i < n_signers; i++) {
+        ARG_CHECK(commitments[i] != NULL);
+    }
+    (void) ctx;
+
+    memset(session, 0, sizeof(*session));
+
+    memcpy(&session->combined_pk, combined_pk, sizeof(*combined_pk));
+    if (n_signers == 0) {
+        return 0;
+    }
+    session->n_signers = (uint32_t) n_signers;
+    secp256k1_musig_signers_init(signers, session->n_signers);
+
+    memcpy(session->pk_hash, pk_hash32, 32);
+    session->nonce_is_set = 0;
+    session->msg_is_set = 0;
+    if (msg32 != NULL) {
+        memcpy(session->msg, msg32, 32);
+        session->msg_is_set = 1;
+    }
+    session->has_secret_data = 0;
+    session->nonce_commitments_hash_is_set = 0;
+
+    for (i = 0; i < n_signers; i++) {
+        memcpy(signers[i].nonce_commitment, commitments[i], 32);
+    }
+    return 1;
+}
+
+int secp256k1_musig_set_nonce(const secp256k1_context* ctx, secp256k1_musig_session_signer_data *signer, const secp256k1_pubkey *nonce) {
+    unsigned char commit[33];
+    size_t commit_size = sizeof(commit);
+    secp256k1_sha256 sha;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(signer != NULL);
+    ARG_CHECK(nonce != NULL);
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_ec_pubkey_serialize(ctx, commit, &commit_size, nonce, SECP256K1_EC_COMPRESSED);
+    secp256k1_sha256_write(&sha, commit, commit_size);
+    secp256k1_sha256_finalize(&sha, commit);
+
+    if (memcmp(commit, signer->nonce_commitment, 32) != 0) {
+        return 0;
+    }
+    memcpy(&signer->nonce, nonce, sizeof(*nonce));
+    signer->present = 1;
+    return 1;
+}
+
+int secp256k1_musig_session_combine_nonces(const secp256k1_context* ctx, secp256k1_musig_session *session, const secp256k1_musig_session_signer_data *signers, size_t n_signers, int *nonce_is_negated, const secp256k1_pubkey *adaptor) {
+    secp256k1_gej combined_noncej;
+    secp256k1_ge combined_noncep;
+    secp256k1_ge noncep;
+    secp256k1_sha256 sha;
+    unsigned char nonce_commitments_hash[32];
+    size_t i;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(signers != NULL);
+
+    if (n_signers != session->n_signers) {
+        return 0;
+    }
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_gej_set_infinity(&combined_noncej);
+    for (i = 0; i < n_signers; i++) {
+        if (!signers[i].present) {
+            return 0;
+        }
+        secp256k1_sha256_write(&sha, signers[i].nonce_commitment, 32);
+        secp256k1_pubkey_load(ctx, &noncep, &signers[i].nonce);
+        secp256k1_gej_add_ge_var(&combined_noncej, &combined_noncej, &noncep, NULL);
+    }
+    secp256k1_sha256_finalize(&sha, nonce_commitments_hash);
+    /* Either the session is a verifier session or or the nonce_commitments_hash has
+     * been set in `musig_session_get_public_nonce`. */
+    VERIFY_CHECK(!session->has_secret_data || session->nonce_commitments_hash_is_set);
+    if (session->has_secret_data
+            && memcmp(session->nonce_commitments_hash, nonce_commitments_hash, 32) != 0) {
+        /* If the signers' commitments changed between get_public_nonce and now we
+         * have to abort because in that case they may have seen our nonce before
+         * creating their commitment. That can happen if the signer_data given to
+         * this function is different to the signer_data given to get_public_nonce.
+         * */
+        return 0;
+    }
+
+    /* Add public adaptor to nonce */
+    if (adaptor != NULL) {
+        secp256k1_pubkey_load(ctx, &noncep, adaptor);
+        secp256k1_gej_add_ge_var(&combined_noncej, &combined_noncej, &noncep, NULL);
+    }
+    secp256k1_ge_set_gej(&combined_noncep, &combined_noncej);
+    if (secp256k1_fe_is_quad_var(&combined_noncep.y)) {
+        session->nonce_is_negated = 0;
+    } else {
+        session->nonce_is_negated = 1;
+        secp256k1_ge_neg(&combined_noncep, &combined_noncep);
+    }
+    if (nonce_is_negated != NULL) {
+        *nonce_is_negated = session->nonce_is_negated;
+    }
+    secp256k1_pubkey_save(&session->combined_nonce, &combined_noncep);
+    session->nonce_is_set = 1;
+    return 1;
+}
+
+int secp256k1_musig_session_set_msg(const secp256k1_context* ctx, secp256k1_musig_session *session, const unsigned char *msg32) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(msg32 != NULL);
+
+    if (session->msg_is_set) {
+        return 0;
+    }
+    memcpy(session->msg, msg32, 32);
+    session->msg_is_set = 1;
+    return 1;
+}
+
+int secp256k1_musig_partial_signature_serialize(const secp256k1_context* ctx, unsigned char *out32, const secp256k1_musig_partial_signature* sig) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(out32 != NULL);
+    ARG_CHECK(sig != NULL);
+    memcpy(out32, sig->data, 32);
+    return 1;
+}
+
+int secp256k1_musig_partial_signature_parse(const secp256k1_context* ctx, secp256k1_musig_partial_signature* sig, const unsigned char *in32) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(in32 != NULL);
+    memcpy(sig->data, in32, 32);
+    return 1;
+}
+
+/* Compute msghash = SHA256(combined_nonce, combined_pk, msg) */
+static int secp256k1_musig_compute_messagehash(const secp256k1_context *ctx, unsigned char *msghash, const secp256k1_musig_session *session) {
+    unsigned char buf[33];
+    size_t bufsize = 33;
+    secp256k1_ge rp;
+    secp256k1_sha256 sha;
+
+    secp256k1_sha256_initialize(&sha);
+    if (!session->nonce_is_set) {
+        return 0;
+    }
+    secp256k1_pubkey_load(ctx, &rp, &session->combined_nonce);
+    secp256k1_fe_get_b32(buf, &rp.x);
+    secp256k1_sha256_write(&sha, buf, 32);
+    secp256k1_ec_pubkey_serialize(ctx, buf, &bufsize, &session->combined_pk, SECP256K1_EC_COMPRESSED);
+    VERIFY_CHECK(bufsize == 33);
+    secp256k1_sha256_write(&sha, buf, bufsize);
+    if (!session->msg_is_set) {
+        return 0;
+    }
+    secp256k1_sha256_write(&sha, session->msg, 32);
+    secp256k1_sha256_finalize(&sha, msghash);
+    return 1;
+}
+
+int secp256k1_musig_partial_sign(const secp256k1_context* ctx, const secp256k1_musig_session *session, secp256k1_musig_partial_signature *partial_sig) {
+    unsigned char msghash[32];
+    int overflow;
+    secp256k1_scalar sk;
+    secp256k1_scalar e, k;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(partial_sig != NULL);
+    ARG_CHECK(session != NULL);
+
+    if (!session->nonce_is_set || !session->has_secret_data) {
+        return 0;
+    }
+
+    /* build message hash */
+    if (!secp256k1_musig_compute_messagehash(ctx, msghash, session)) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&e, msghash, NULL);
+
+    secp256k1_scalar_set_b32(&sk, session->seckey, &overflow);
+    if (overflow) {
+        secp256k1_scalar_clear(&sk);
+        return 0;
+    }
+
+    secp256k1_scalar_set_b32(&k, session->secnonce, &overflow);
+    if (overflow || secp256k1_scalar_is_zero(&k)) {
+        secp256k1_scalar_clear(&sk);
+        secp256k1_scalar_clear(&k);
+        return 0;
+    }
+    if (session->nonce_is_negated) {
+        secp256k1_scalar_negate(&k, &k);
+    }
+
+    /* Sign */
+    secp256k1_scalar_mul(&e, &e, &sk);
+    secp256k1_scalar_add(&e, &e, &k);
+    secp256k1_scalar_get_b32(&partial_sig->data[0], &e);
+    secp256k1_scalar_clear(&sk);
+    secp256k1_scalar_clear(&k);
+
+    return 1;
+}
+
+int secp256k1_musig_partial_sig_combine(const secp256k1_context* ctx, const secp256k1_musig_session *session, secp256k1_schnorrsig *sig, const secp256k1_musig_partial_signature *partial_sigs, size_t n_sigs) {
+    size_t i;
+    secp256k1_scalar s;
+    secp256k1_ge noncep;
+    (void) ctx;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(partial_sigs != NULL);
+    ARG_CHECK(session != NULL);
+
+    if (!session->nonce_is_set) {
+        return 0;
+    }
+    if (n_sigs != session->n_signers) {
+        return 0;
+    }
+    secp256k1_scalar_clear(&s);
+    for (i = 0; i < n_sigs; i++) {
+        int overflow;
+        secp256k1_scalar term;
+
+        secp256k1_scalar_set_b32(&term, partial_sigs[i].data, &overflow);
+        if (overflow) {
+            return 0;
+        }
+        secp256k1_scalar_add(&s, &s, &term);
+    }
+
+    secp256k1_pubkey_load(ctx, &noncep, &session->combined_nonce);
+    VERIFY_CHECK(secp256k1_fe_is_quad_var(&noncep.y));
+    secp256k1_fe_normalize(&noncep.x);
+    secp256k1_fe_get_b32(&sig->data[0], &noncep.x);
+    secp256k1_scalar_get_b32(&sig->data[32], &s);
+
+    return 1;
+}
+
+int secp256k1_musig_partial_sig_verify(const secp256k1_context* ctx, const secp256k1_musig_session *session, const secp256k1_musig_session_signer_data *signer, const secp256k1_musig_partial_signature *partial_sig, const secp256k1_pubkey *pubkey) {
+    unsigned char msghash[32];
+    secp256k1_scalar s;
+    secp256k1_scalar e;
+    secp256k1_scalar mu;
+    secp256k1_gej rj;
+    secp256k1_ge rp;
+    int overflow;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(session != NULL);
+    ARG_CHECK(signer != NULL);
+    ARG_CHECK(partial_sig != NULL);
+    ARG_CHECK(pubkey != NULL);
+
+    if (!session->nonce_is_set || !signer->present) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&s, partial_sig->data, &overflow);
+    if (overflow) {
+        return 0;
+    }
+    if (!secp256k1_musig_compute_messagehash(ctx, msghash, session)) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&e, msghash, NULL);
+
+    /* Multiplying the messagehash by the musig coefficient is equivalent
+     * to multiplying the signer's public key by the coefficient, except
+     * much easier to do. */
+    secp256k1_musig_coefficient(&mu, session->pk_hash, signer->index);
+    secp256k1_scalar_mul(&e, &e, &mu);
+
+    if (!secp256k1_pubkey_load(ctx, &rp, &signer->nonce)) {
+        return 0;
+    }
+
+    if (!secp256k1_schnorrsig_real_verify(ctx, &rj, &s, &e, pubkey)) {
+        return 0;
+    }
+    if (!session->nonce_is_negated) {
+        secp256k1_ge_neg(&rp, &rp);
+    }
+    secp256k1_gej_add_ge_var(&rj, &rj, &rp, NULL);
+
+    return secp256k1_gej_is_infinity(&rj);
+}
+
+int secp256k1_musig_partial_sig_adapt(const secp256k1_context* ctx, secp256k1_musig_partial_signature *adaptor_sig, const secp256k1_musig_partial_signature *partial_sig, const unsigned char *sec_adaptor32, int nonce_is_negated) {
+    secp256k1_scalar s;
+    secp256k1_scalar t;
+    int overflow;
+
+    (void) ctx;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(adaptor_sig != NULL);
+    ARG_CHECK(partial_sig != NULL);
+    ARG_CHECK(sec_adaptor32 != NULL);
+
+    secp256k1_scalar_set_b32(&s, partial_sig->data, &overflow);
+    if (overflow) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&t, sec_adaptor32, &overflow);
+    if (overflow) {
+        secp256k1_scalar_clear(&t);
+        return 0;
+    }
+
+    if (nonce_is_negated) {
+        secp256k1_scalar_negate(&t, &t);
+    }
+
+    secp256k1_scalar_add(&s, &s, &t);
+    secp256k1_scalar_get_b32(adaptor_sig->data, &s);
+    secp256k1_scalar_clear(&t);
+    return 1;
+}
+
+int secp256k1_musig_extract_secret_adaptor(const secp256k1_context* ctx, unsigned char *sec_adaptor32, const secp256k1_schnorrsig *sig, const secp256k1_musig_partial_signature *partial_sigs, size_t n_partial_sigs, int nonce_is_negated) {
+    secp256k1_scalar t;
+    secp256k1_scalar s;
+    int overflow;
+    size_t i;
+
+    (void) ctx;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(sec_adaptor32 != NULL);
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(partial_sigs != NULL);
+
+    secp256k1_scalar_set_b32(&t, &sig->data[32], &overflow);
+    if (overflow) {
+        return 0;
+    }
+    secp256k1_scalar_negate(&t, &t);
+
+    for (i = 0; i < n_partial_sigs; i++) {
+        secp256k1_scalar_set_b32(&s, partial_sigs[i].data, &overflow);
+        if (overflow) {
+            secp256k1_scalar_clear(&t);
+            return 0;
+        }
+        secp256k1_scalar_add(&t, &t, &s);
+    }
+
+    if (!nonce_is_negated) {
+        secp256k1_scalar_negate(&t, &t);
+    }
+    secp256k1_scalar_get_b32(sec_adaptor32, &t);
+    secp256k1_scalar_clear(&t);
+    return 1;
+}
+
+#endif

src/modules/musig/musig.md

@@ -0,0 +1,199 @@
+MuSig - Rogue-Key-Resistant Multisignatures Module
+===========================
+
+This module implements the MuSig [1] multisignature scheme. The majority of
+the module is an API designed to be used by signing or auditing participants
+in a multisignature scheme. This involves a somewhat complex state machine
+and significant effort has been taken to prevent accidental misuse of the
+API in ways that could lead to accidental signatures or loss of key material.
+
+The resulting signatures are valid Schnorr signatures as described in [2].
+
+# Theory
+
+In MuSig all signers contribute key material to a single signing key,
+using the equation
+
+    P = sum_i µ_i - P_i
+
+where `P_i` is the public key of the `i`th signer and `µ_i` is a so-called
+_MuSig coefficient_ computed according to the following equation
+
+    L = H(P_1 || P_2 || ... || P_n)
+    µ_i = H(L || i)
+
+where H is a hash function modelled as a random oracle.
+
+To produce a multisignature `(s, R)` on a message `m` using verification key
+`P`, signers act as follows:
+
+1. Each computes a nonce, or ephemeral keypair, `(k_i, R_i)`. Every signer
+   communicates `H(R_i)` to every participant (both signers and auditors).
+2. Upon receipt of every `H(R_i)`, each signer communicates `R_i` to every
+   participant. The recipients check that each `R_i` is consistent with the
+   previously-communicated hash.
+3. Each signer computes a combined nonce
+    `R = sum_i R_i`
+   and shared challenge
+    `e = H(R || P || m)`
+   and partial signature
+    `s_i = k_i + µ_i*x_i*e`
+   where `x_i` is the secret key corresponding to `P_i`.
+
+The complete signature is then the `(s, R)` where `s = sum_i s_i` and `R = sum_i R_i`.
+
+# API Usage
+
+The following sections describe use of our API, and are mirrored in code in `src/modules/musig/example.c`.
+
+It is essential to security that signers use a unique uniformly random nonce for all
+signing sessions, and that they do not reuse these nonces even in the case that a
+signing session fails to complete. To that end, all signing state is encapsulated
+in the data structure `secp256k1_musig_session`. The API does not expose any
+functionality to serialize or deserialize this structure; it is designed to exist
+only in memory.
+
+Users who need to persist this structure must take additional security measures
+which cannot be enforced by a C API. Some guidance is provided in the documentation
+for this data structure in `include/secp256k1_musig.h`.
+
+## Key Generation
+
+To use MuSig, users must first compute their combined public key `P`, which is
+suitable for use on a blockchain or other public key repository. They do this
+by calling `secp256k1_musig_pubkey_combine`.
+
+This function takes as input a list of public keys `P_i` in the argument
+`pubkeys`. It outputs the combined public key `P` in the out-pointer `combined_pk`
+and hash `L` in the out-pointer `pk_hash32`, if this pointer is non-NULL.
+
+## Signing
+
+A participant who wishes to sign a message (as opposed to observing/auditing the
+signature process, which is also a supported mode) acts as follows.
+
+### Signing Participant
+
+1. The signer starts the session by calling `secp256k1_musig_session_initialize`.
+   This function outputs
+   - an initialized session state in the out-pointer `session`
+   - an array of initialized signer data in the out-pointer `signers`
+   - a commitment `H(R_i)` to a nonce in the out-pointer `nonce_commitment32`
+   It takes as input
+   - a unique session ID `session_id32`
+   - (optionally) a message to be signed `msg32`
+   - the combined public key output from `secp256k1_musig_pubkey_combine`
+   - the public key hash output from `secp256k1_musig_pubkey_combine`
+   - the signer's index `i` `my_index`
+   - the signer's secret key `seckey`
+2. The signer then communicates `H(R_i)` to all other signers, and receives
+   commitments `H(R_j)` from all other signers `j`. These hashes are simply
+   length-32 byte arrays which can be communicated however is communicated.
+3. Once all signers nonce commitments have been received, the signer records
+   these commitments with the function `secp256k1_musig_session_get_public_nonce`.
+   This function updates in place
+   - the session state `session`
+   - the array of signer data `signers`
+   taking in as input the list of commitments `commitments` and outputting the
+   signer's public nonce `R_i` in the out-pointer `nonce`.
+4. The signer then communicates `R_i` to all other signers, and receives `R_j`
+   from each signer `j`. On receipt of a nonce `R_j` he calls the function
+   `secp256k1_musig_set_nonce` to record this fact. This function checks that
+   the received nonce is consistent with the previously-received nonce and will
+   return 0 in this case. The signer must also call this function with his own
+   nonce and his own index `i`.
+   These nonces `R_i` are secp256k1 public keys; they should be serialized using
+   `secp256k1_ec_pubkey_serialize` and parsed with `secp256k1_ec_pubkey_parse`.
+5. Once all nonces have been exchanged in this way, signers are able to compute
+   their partial signatures. They do so by calling `secp256k1_musig_session_combine_nonces`
+   which updates in place
+   - the session state `session`
+   - the array of signer data `signers`
+   It outputs an auxiliary integer `nonce_is_negated` and has an auxiliary input
+   `adaptor`. Both of these may be set to NULL for ordinary signing purposes.
+   If the signer did not provide a message to `secp256k1_musig_session_initialize`,
+   a message must be provided now by calling `secp256k1_musig_session_set_msg` which
+   updates the session state in place.
+6. The signer computes a partial signature `s_i` using the function
+   `secp256k1_musig_partial_sign` which takes the session state as input and
+   partial signature as output.
+7. The signer then communicates the partial signature `s_i` to all other signers, or
+   to a central coordinator. These partial signatures should be serialized using
+   `musig_partial_signature_serialize` and parsed using `musig_partial_signature_parse`.
+8. Each signer calls `secp256k1_musig_partial_sig_verify` on the other signers' partial
+   signatures to verify their correctness. If only the validity of the final signature
+   is important, not assigning blame, this step can be skipped.
+9. Any signer, or central coordinator, may combine the partial signatures to obtain
+   a complete signature using `secp256k1_musig_partial_sig_combine`. This function takes
+   a signing session and array of MuSig partial signatures, and outputs a single
+   Schnorr signature.
+
+### Non-signing Participant
+
+A participant who wants to verify the signing process, i.e. check that nonce commitments
+are consistent and partial signatures are correct without contributing a partial signature,
+may do so using the above instructions except for the following changes:
+
+1. A signing session should be produced using `musig_session_initialize_verifier`
+   rather than `musig_session_initialize`; this function takes no secret data or
+   signer index.
+2. The participant receives nonce commitments, public nonces and partial signatures,
+   but does not produce these values. Therefore `secp256k1_musig_session_get_public_nonce`
+   and `secp256k1_musig_partial_sign` are not called.
+
+### Verifier
+
+The final signature is simply a valid Schnorr signature using the combined public key. It
+can be verified using the `secp256k1_schnorrsig_verify` with the correct message and
+public key output from `secp256k1_musig_pubkey_combine`.
+
+## Atomic Swaps
+
+The signing API supports the production of "adaptor signatures", modified partial signatures
+which are offset by an auxiliary secret known to one party. That is,
+1. One party generates a (secret) adaptor `t` with corresponding (public) adaptor `T = t*G`.
+2. When combining nonces, each party adds `T` to the total nonce used in the signature.
+3. The party who knows `t` must "adapt" their partial signature with `t` to complete the
+   signature.
+4. Any party who sees both the final signature and the original partial signatures
+   can compute `t`.
+
+Using these adaptor signatures, two 2-of-2 MuSig signing protocols can be executed in
+parallel such that one party's partial signatures are made atomic. That is, when the other
+party learns one partial signature, she automatically learns the other. This has applications
+in cross-chain atomic swaps.
+
+Such a protocol can be executed as follows. Consider two participants, Alice and Bob, who
+are simultaneously producing 2-of-2 multisignatures for two blockchains A and B. They act
+as follows.
+
+1. Before the protocol begins, Bob chooses a 32-byte auxiliary secret `t` at random and
+   computes a corresponding public point `T` by calling `secp256k1_ec_pubkey_create`.
+   He communicates `T` to Alice.
+2. Together, the parties execute steps 1-4 of the signing protocol above.
+3. At step 5, when combining the two parties' public nonces, both parties call
+   `secp256k1_musig_session_combine_nonces` with `adaptor` set to `T` and `nonce_is_negated`
+   set to a non-NULL pointer to int.
+4. Steps 6 and 7 proceed as before. Step 8, verifying the partial signatures, is now
+   essential to the security of the protocol and must not be omitted!
+
+The above steps are executed identically for both signing sessions. However, step 9 will
+not work as before, since the partial signatures will not add up to a valid total signature.
+Additional steps must be taken, and it is at this point that the two signing sessions
+diverge. From here on we consider "Session A" which benefits Alice (e.g. which sends her
+coins) and "Session B" which benefits Bob (e.g. which sends him coins).
+
+5. In Session B, Bob calls `secp256k1_musig_partial_sig_adapt` with his partial signature
+   and `t`, to produce an adaptor signature. He can then call `secp256k1_musig_partial_sig_combine`
+   with this adaptor signature and Alice's partial signature, to produce a complete
+   signature for blockchain B.
+6. Alice reads this signature from blockchain B. She calls `secp256k1_musig_extract_secret_adaptor`,
+   passing the complete signature along with her and Bob's partial signatures from Session B.
+   This function outputs `t`, which until this point was only known to Bob.
+7. In Session A, Alice is now able to replicate Bob's action, calling
+   `secp256k1_musig_partial_sig_adapt` with her own partial signature and `t`, ultimately
+   producing a complete signature on blockchain A.
+
+[1] https://eprint.iacr.org/2018/068
+[2] https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki
+

src/modules/musig/tests_impl.h

@@ -0,0 +1,757 @@
+/**********************************************************************
+ * Copyright (c) 2018 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_MODULE_MUSIG_TESTS_
+#define _SECP256K1_MODULE_MUSIG_TESTS_
+
+#include "secp256k1_musig.h"
+
+void musig_api_tests(secp256k1_scratch_space *scratch) {
+    secp256k1_scratch_space *scratch_small;
+    secp256k1_musig_session session[2];
+    secp256k1_musig_session verifier_session;
+    secp256k1_musig_session_signer_data signer0[2];
+    secp256k1_musig_session_signer_data signer1[2];
+    secp256k1_musig_session_signer_data verifier_signer_data[2];
+    secp256k1_musig_partial_signature partial_sig[2];
+    secp256k1_musig_partial_signature partial_sig_adapted[2];
+    secp256k1_musig_partial_signature partial_sig_overflow;
+    secp256k1_schnorrsig final_sig;
+    secp256k1_schnorrsig final_sig_cmp;
+
+    unsigned char buf[32];
+    unsigned char sk[2][32];
+    unsigned char ones[32];
+    unsigned char session_id[2][32];
+    unsigned char nonce_commitment[2][32];
+    int nonce_is_negated;
+    const unsigned char *ncs[2];
+    unsigned char msg[32];
+    unsigned char msghash[32];
+    secp256k1_pubkey combined_pk;
+    unsigned char pk_hash[32];
+    secp256k1_pubkey pk[2];
+
+    unsigned char sec_adaptor[32];
+    unsigned char sec_adaptor1[32];
+    secp256k1_pubkey adaptor;
+
+    /** setup **/
+    secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
+    secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    int ecount;
+
+    secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount);
+
+    memset(ones, 0xff, 32);
+
+    secp256k1_rand256(session_id[0]);
+    secp256k1_rand256(session_id[1]);
+    secp256k1_rand256(sk[0]);
+    secp256k1_rand256(sk[1]);
+    secp256k1_rand256(msg);
+    secp256k1_rand256(sec_adaptor);
+
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk[0], sk[0]) == 1);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk[1], sk[1]) == 1);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &adaptor, sec_adaptor) == 1);
+
+    /** main test body **/
+
+    /* Key combination */
+    ecount = 0;
+    CHECK(secp256k1_musig_pubkey_combine(none, scratch, &combined_pk, pk_hash, pk, 2) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_pubkey_combine(sign, scratch, &combined_pk, pk_hash, pk, 2) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, pk, 2) == 1);
+    CHECK(ecount == 2);
+    /* pubkey_combine does not require a scratch space */
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, NULL, &combined_pk, pk_hash, pk, 2) == 1);
+    CHECK(ecount == 2);
+    /* If a scratch space is given it shouldn't be too small */
+    scratch_small = secp256k1_scratch_space_create(ctx, 1);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch_small, &combined_pk, pk_hash, pk, 2) == 0);
+    secp256k1_scratch_space_destroy(scratch_small);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, NULL, pk_hash, pk, 2) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, NULL, pk, 2) == 1);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, NULL, 2) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, pk, 0) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, NULL, 0) == 0);
+    CHECK(ecount == 6);
+
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, pk, 2) == 1);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, pk, 2) == 1);
+    CHECK(secp256k1_musig_pubkey_combine(vrfy, scratch, &combined_pk, pk_hash, pk, 2) == 1);
+
+    /** Session creation **/
+    ecount = 0;
+    CHECK(secp256k1_musig_session_initialize(none, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_session_initialize(vrfy, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_session_initialize(sign, NULL, signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], NULL, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, NULL, session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], NULL, msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], NULL, &combined_pk, pk_hash, 2, 0, sk[0]) == 1);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, NULL, pk_hash, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 7);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, NULL, 2, 0, sk[0]) == 0);
+    CHECK(ecount == 8);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 0, 0, sk[0]) == 0);
+    CHECK(ecount == 8);
+    /* If more than UINT32_MAX fits in a size_t, test that session_initialize
+     * rejects n_signers that high. */
+    if (SIZE_MAX > UINT32_MAX) {
+        CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, ((size_t) UINT32_MAX) + 2, 0, sk[0]) == 0);
+    }
+    CHECK(ecount == 8);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, NULL) == 0);
+    CHECK(ecount == 9);
+    /* secret key overflows */
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, ones) == 0);
+    CHECK(ecount == 9);
+
+
+    {
+        secp256k1_musig_session session_without_msg;
+        CHECK(secp256k1_musig_session_initialize(sign, &session_without_msg, signer0, nonce_commitment[0], session_id[0], NULL, &combined_pk, pk_hash, 2, 0, sk[0]) == 1);
+        CHECK(secp256k1_musig_session_set_msg(none, &session_without_msg, msg) == 1);
+        CHECK(secp256k1_musig_session_set_msg(none, &session_without_msg, msg) == 0);
+    }
+    CHECK(secp256k1_musig_session_initialize(sign, &session[0], signer0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 1);
+    CHECK(secp256k1_musig_session_initialize(sign, &session[1], signer1, nonce_commitment[1], session_id[1], msg, &combined_pk, pk_hash, 2, 1, sk[1]) == 1);
+    ncs[0] = nonce_commitment[0];
+    ncs[1] = nonce_commitment[1];
+
+    ecount = 0;
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, pk_hash, ncs, 2) == 1);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, NULL, verifier_signer_data, msg, &combined_pk, pk_hash, ncs, 2) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, NULL, &combined_pk, pk_hash, ncs, 2) == 1);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, NULL, pk_hash, ncs, 2) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, NULL, ncs, 2) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, pk_hash, NULL, 2) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, pk_hash, ncs, 0) == 0);
+    CHECK(ecount == 4);
+    if (SIZE_MAX > UINT32_MAX) {
+        CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, pk_hash, ncs, ((size_t) UINT32_MAX) + 2) == 0);
+    }
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_session_initialize_verifier(none, &verifier_session, verifier_signer_data, msg, &combined_pk, pk_hash, ncs, 2) == 1);
+
+    CHECK(secp256k1_musig_compute_messagehash(none, msghash, &verifier_session) == 0);
+    CHECK(secp256k1_musig_compute_messagehash(none, msghash, &session[0]) == 0);
+
+    /** Signing step 0 -- exchange nonce commitments */
+    ecount = 0;
+    {
+        secp256k1_pubkey nonce;
+
+        /* Can obtain public nonce after commitments have been exchanged; still can't sign */
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, &nonce, ncs, 2) == 1);
+        CHECK(secp256k1_musig_partial_sign(none, &session[0], &partial_sig[0]) == 0);
+        CHECK(ecount == 0);
+    }
+
+    /** Signing step 1 -- exchange nonces */
+    ecount = 0;
+    {
+        secp256k1_pubkey public_nonce[3];
+
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, &public_nonce[0], ncs, 2) == 1);
+        CHECK(ecount == 0);
+        CHECK(secp256k1_musig_session_get_public_nonce(none, NULL, signer0, &public_nonce[0], ncs, 2) == 0);
+        CHECK(ecount == 1);
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], NULL, &public_nonce[0], ncs, 2) == 0);
+        CHECK(ecount == 2);
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, NULL, ncs, 2) == 0);
+        CHECK(ecount == 3);
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, &public_nonce[0], NULL, 2) == 0);
+        CHECK(ecount == 4);
+        /* Number of commitments and number of signers are different */
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, &public_nonce[0], ncs, 1) == 0);
+        CHECK(ecount == 4);
+
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[0], signer0, &public_nonce[0], ncs, 2) == 1);
+        CHECK(secp256k1_musig_session_get_public_nonce(none, &session[1], signer1, &public_nonce[1], ncs, 2) == 1);
+
+        CHECK(secp256k1_musig_set_nonce(none, &signer0[0], &public_nonce[0]) == 1);
+        CHECK(secp256k1_musig_set_nonce(none, &signer0[1], &public_nonce[0]) == 0);
+        CHECK(secp256k1_musig_set_nonce(none, &signer0[1], &public_nonce[1]) == 1);
+        CHECK(secp256k1_musig_set_nonce(none, &signer0[1], &public_nonce[1]) == 1);
+        CHECK(ecount == 4);
+
+        CHECK(secp256k1_musig_set_nonce(none, NULL, &public_nonce[0]) == 0);
+        CHECK(ecount == 5);
+        CHECK(secp256k1_musig_set_nonce(none, &signer1[0], NULL) == 0);
+        CHECK(ecount == 6);
+
+        CHECK(secp256k1_musig_set_nonce(none, &signer1[0], &public_nonce[0]) == 1);
+        CHECK(secp256k1_musig_set_nonce(none, &signer1[1], &public_nonce[1]) == 1);
+        CHECK(secp256k1_musig_set_nonce(none, &verifier_signer_data[0], &public_nonce[0]) == 1);
+        CHECK(secp256k1_musig_set_nonce(none, &verifier_signer_data[1], &public_nonce[1]) == 1);
+
+        ecount = 0;
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], signer0, 2, &nonce_is_negated, &adaptor) == 1);
+        CHECK(secp256k1_musig_session_combine_nonces(none, NULL, signer0, 2, &nonce_is_negated, &adaptor) == 0);
+        CHECK(ecount == 1);
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], NULL, 2, &nonce_is_negated, &adaptor) == 0);
+        CHECK(ecount == 2);
+        /* Number of signers differs from number during intialization */
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], signer0, 1, &nonce_is_negated, &adaptor) == 0);
+        CHECK(ecount == 2);
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], signer0, 2, NULL, &adaptor) == 1);
+        CHECK(ecount == 2);
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], signer0, 2, &nonce_is_negated, NULL) == 1);
+
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[0], signer0, 2, &nonce_is_negated, &adaptor) == 1);
+        CHECK(secp256k1_musig_session_combine_nonces(none, &session[1], signer0, 2, &nonce_is_negated, &adaptor) == 1);
+        CHECK(secp256k1_musig_session_combine_nonces(none, &verifier_session, verifier_signer_data, 2, &nonce_is_negated, &adaptor) == 1);
+    }
+
+    /** Signing step 2 -- partial signatures */
+    ecount = 0;
+    CHECK(secp256k1_musig_partial_sign(none, &session[0], &partial_sig[0]) == 1);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_musig_partial_sign(none, NULL, &partial_sig[0]) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_partial_sign(none, &session[0], NULL) == 0);
+    CHECK(ecount == 2);
+
+    CHECK(secp256k1_musig_partial_sign(none, &session[0], &partial_sig[0]) == 1);
+    CHECK(secp256k1_musig_partial_sign(none, &session[1], &partial_sig[1]) == 1);
+    /* observer can't sign */
+    CHECK(secp256k1_musig_partial_sign(none, &verifier_session, &partial_sig[2]) == 0);
+    CHECK(ecount == 2);
+
+    ecount = 0;
+    CHECK(secp256k1_musig_partial_signature_serialize(none, buf, &partial_sig[0]) == 1);
+    CHECK(secp256k1_musig_partial_signature_serialize(none, NULL, &partial_sig[0]) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_partial_signature_serialize(none, buf, NULL) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_signature_parse(none, &partial_sig[0], buf) == 1);
+    CHECK(secp256k1_musig_partial_signature_parse(none, NULL, buf) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_partial_signature_parse(none, &partial_sig[0], NULL) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_partial_signature_parse(none, &partial_sig_overflow, ones) == 1);
+
+    /** Partial signature verification */
+    ecount = 0;
+    CHECK(secp256k1_musig_partial_sig_verify(none, &session[0], &signer0[0], &partial_sig[0], &pk[0]) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(sign, &session[0], &signer0[0], &partial_sig[0], &pk[0]) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], &partial_sig[0], &pk[0]) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], &partial_sig[1], &pk[0]) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, NULL, &signer0[0], &partial_sig[0], &pk[0]) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], NULL, &partial_sig[0], &pk[0]) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], NULL, &pk[0]) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], &partial_sig_overflow, &pk[0]) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], &partial_sig[0], NULL) == 0);
+    CHECK(ecount == 6);
+
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[0], &partial_sig[0], &pk[0]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[1], &signer1[0], &partial_sig[0], &pk[0]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[0], &signer0[1], &partial_sig[1], &pk[1]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &session[1], &signer1[1], &partial_sig[1], &pk[1]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &verifier_session, &verifier_signer_data[0], &partial_sig[0], &pk[0]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(vrfy, &verifier_session, &verifier_signer_data[1], &partial_sig[1], &pk[1]) == 1);
+    CHECK(ecount == 6);
+
+    /** Adaptor signature verification */
+    memcpy(&partial_sig_adapted[1], &partial_sig[1], sizeof(partial_sig_adapted[1]));
+    ecount = 0;
+    CHECK(secp256k1_musig_partial_sig_adapt(none, &partial_sig_adapted[0], &partial_sig[0], sec_adaptor, nonce_is_negated) == 1);
+    CHECK(secp256k1_musig_partial_sig_adapt(none, NULL, &partial_sig[0], sec_adaptor, 0) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_partial_sig_adapt(none, &partial_sig_adapted[0], NULL, sec_adaptor, 0) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_adapt(none, &partial_sig_adapted[0], &partial_sig_overflow, sec_adaptor, nonce_is_negated) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_adapt(none, &partial_sig_adapted[0], &partial_sig[0], NULL, 0) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_partial_sig_adapt(none, &partial_sig_adapted[0], &partial_sig[0], ones, nonce_is_negated) == 0);
+    CHECK(ecount == 3);
+
+    /** Signing combining and verification */
+    ecount = 0;
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig, partial_sig_adapted, 2) == 1);
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig_cmp, partial_sig_adapted, 2) == 1);
+    CHECK(memcmp(&final_sig, &final_sig_cmp, sizeof(final_sig)) == 0);
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig_cmp, partial_sig_adapted, 2) == 1);
+    CHECK(memcmp(&final_sig, &final_sig_cmp, sizeof(final_sig)) == 0);
+
+    CHECK(secp256k1_musig_partial_sig_combine(none, NULL, &final_sig, partial_sig_adapted, 2) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], NULL, partial_sig_adapted, 2) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig, NULL, 2) == 0);
+    CHECK(ecount == 3);
+    {
+        secp256k1_musig_partial_signature partial_sig_tmp[2];
+        partial_sig_tmp[0] = partial_sig_adapted[0];
+        partial_sig_tmp[1] = partial_sig_overflow;
+        CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig, partial_sig_tmp, 2) == 0);
+    }
+    CHECK(ecount == 3);
+    /* Wrong number of partial sigs */
+    CHECK(secp256k1_musig_partial_sig_combine(none, &session[0], &final_sig, partial_sig_adapted, 1) == 0);
+    CHECK(ecount == 3);
+
+    CHECK(secp256k1_schnorrsig_verify(vrfy, &final_sig, msg, &combined_pk) == 1);
+
+    /** Secret adaptor can be extracted from signature */
+    ecount = 0;
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig, partial_sig, 2, nonce_is_negated) == 1);
+    CHECK(memcmp(sec_adaptor, sec_adaptor1, 32) == 0);
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, NULL, &final_sig, partial_sig, 2, 0) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, NULL, partial_sig, 2, 0) == 0);
+    CHECK(ecount == 2);
+    {
+        secp256k1_schnorrsig final_sig_tmp = final_sig;
+        memcpy(&final_sig_tmp.data[32], ones, 32);
+        CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig_tmp, partial_sig, 2, nonce_is_negated) == 0);
+    }
+    CHECK(ecount == 2);
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig, NULL, 2, 0) == 0);
+    CHECK(ecount == 3);
+    {
+        secp256k1_musig_partial_signature partial_sig_tmp[2];
+        partial_sig_tmp[0] = partial_sig[0];
+        partial_sig_tmp[1] = partial_sig_overflow;
+        CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig, partial_sig_tmp, 2, nonce_is_negated) == 0);
+    }
+    CHECK(ecount == 3);
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig, partial_sig, 0, 0) == 1);
+    CHECK(secp256k1_musig_extract_secret_adaptor(none, sec_adaptor1, &final_sig, partial_sig, 2, 1) == 1);
+
+    /** cleanup **/
+    memset(&session, 0, sizeof(session));
+    secp256k1_context_destroy(none);
+    secp256k1_context_destroy(sign);
+    secp256k1_context_destroy(vrfy);
+}
+
+/* Initializes two sessions, one use the given parameters (session_id,
+ * nonce_commitments, etc.) except that `session_tmp` uses new signers with different
+ * public keys. The point of this test is to call `musig_session_get_public_nonce`
+ * with signers from `session_tmp` who have different public keys than the correct
+ * ones and return the resulting messagehash. This should not result in a different
+ * messagehash because the public keys of the signers are only used during session
+ * initialization. */
+int musig_state_machine_diff_signer_msghash_test(unsigned char *msghash, secp256k1_pubkey *pks, secp256k1_pubkey *combined_pk, unsigned char *pk_hash, const unsigned char * const *nonce_commitments, unsigned char *msg, secp256k1_pubkey *nonce_other, unsigned char *sk, unsigned char *session_id) {
+    secp256k1_musig_session session;
+    secp256k1_musig_session session_tmp;
+    unsigned char nonce_commitment[32];
+    secp256k1_musig_session_signer_data signers[2];
+    secp256k1_musig_session_signer_data signers_tmp[2];
+    unsigned char sk_dummy[32];
+    secp256k1_pubkey pks_tmp[2];
+    secp256k1_pubkey combined_pk_tmp;
+    unsigned char pk_hash_tmp[32];
+    secp256k1_pubkey nonce;
+
+    /* Set up signers with different public keys */
+    secp256k1_rand256(sk_dummy);
+    pks_tmp[0] = pks[0];
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pks_tmp[1], sk_dummy) == 1);
+    CHECK(secp256k1_musig_pubkey_combine(ctx, NULL, &combined_pk_tmp, pk_hash_tmp, pks_tmp, 2) == 1);
+    CHECK(secp256k1_musig_session_initialize(ctx, &session_tmp, signers_tmp, nonce_commitment, session_id, msg, &combined_pk_tmp, pk_hash_tmp, 2, 0, sk_dummy) == 1);
+
+    CHECK(secp256k1_musig_session_initialize(ctx, &session, signers, nonce_commitment, session_id, msg, combined_pk, pk_hash, 2, 0, sk) == 1);
+    CHECK(memcmp(nonce_commitment, nonce_commitments[1], 32) == 0);
+    /* Call get_public_nonce with different signers than the signers the session was
+     * initialized with. */
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session_tmp, signers, &nonce, nonce_commitments, 2) == 1);
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session, signers_tmp, &nonce, nonce_commitments, 2) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[0], nonce_other) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[1], &nonce) == 1);
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &session, signers, 2, NULL, NULL) == 1);
+
+    return secp256k1_musig_compute_messagehash(ctx, msghash, &session);
+}
+
+/* Creates a new session (with a different session id) and tries to use that session
+ * to combine nonces with given signers_other. This should fail, because the nonce
+ * commitments of signers_other do not match the nonce commitments the new session
+ * was initialized with. If do_test is 0, the correct signers are being used and
+ * therefore the function should return 1. */
+int musig_state_machine_diff_signers_combine_nonce_test(secp256k1_pubkey *combined_pk, unsigned char *pk_hash, unsigned char *nonce_commitment_other, secp256k1_pubkey *nonce_other, unsigned char *msg, unsigned char *sk, secp256k1_musig_session_signer_data *signers_other, int do_test) {
+    secp256k1_musig_session session;
+    secp256k1_musig_session_signer_data signers[2];
+    secp256k1_musig_session_signer_data *signers_to_use;
+    unsigned char nonce_commitment[32];
+    unsigned char session_id[32];
+    secp256k1_pubkey nonce;
+    const unsigned char *ncs[2];
+
+    /* Initialize new signers */
+    secp256k1_rand256(session_id);
+    CHECK(secp256k1_musig_session_initialize(ctx, &session, signers, nonce_commitment, session_id, msg, combined_pk, pk_hash, 2, 1, sk) == 1);
+    ncs[0] = nonce_commitment_other;
+    ncs[1] = nonce_commitment;
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session, signers, &nonce, ncs, 2) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[0], nonce_other) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[1], &nonce) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[1], &nonce) == 1);
+    secp256k1_musig_session_combine_nonces(ctx, &session, signers_other, 2, NULL, NULL);
+    if (do_test) {
+        signers_to_use = signers_other;
+    } else {
+        signers_to_use = signers;
+    }
+    return secp256k1_musig_session_combine_nonces(ctx, &session, signers_to_use, 2, NULL, NULL);
+}
+
+/* Recreates a session with the given session_id, signers, pk, msg etc. parameters
+ * and tries to sign and verify the other signers partial signature. Both should fail
+ * if msg is NULL. */
+int musig_state_machine_missing_msg_test(secp256k1_pubkey *pks, secp256k1_pubkey *combined_pk, unsigned char *pk_hash, unsigned char *nonce_commitment_other, secp256k1_pubkey *nonce_other, secp256k1_musig_partial_signature *partial_sig_other, unsigned char *sk, unsigned char *session_id, unsigned char *msg) {
+    secp256k1_musig_session session;
+    secp256k1_musig_session_signer_data signers[2];
+    unsigned char nonce_commitment[32];
+    const unsigned char *ncs[2];
+    secp256k1_pubkey nonce;
+    secp256k1_musig_partial_signature partial_sig;
+    int partial_sign, partial_verify;
+
+    CHECK(secp256k1_musig_session_initialize(ctx, &session, signers, nonce_commitment, session_id, msg, combined_pk, pk_hash, 2, 0, sk) == 1);
+    ncs[0] = nonce_commitment_other;
+    ncs[1] = nonce_commitment;
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session, signers, &nonce, ncs, 2) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[0], nonce_other) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[1], &nonce) == 1);
+
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &session, signers, 2, NULL, NULL) == 1);
+    partial_sign = secp256k1_musig_partial_sign(ctx, &session, &partial_sig);
+    partial_verify = secp256k1_musig_partial_sig_verify(ctx, &session, &signers[0], partial_sig_other, &pks[0]);
+    if (msg != NULL) {
+        /* Return 1 if both succeeded */
+        return partial_sign && partial_verify;
+    }
+    /* Return 0 if both failed */
+    return partial_sign || partial_verify;
+}
+
+/* Recreates a session with the given session_id, signers, pk, msg etc. parameters
+ * and tries to verify and combine partial sigs. If do_combine is 0, the
+ * combine_nonces step is left out. In that case verify and combine should fail and
+ * this function should return 0. */
+int musig_state_machine_missing_combine_test(secp256k1_pubkey *pks, secp256k1_pubkey *combined_pk, unsigned char *pk_hash, unsigned char *nonce_commitment_other, secp256k1_pubkey *nonce_other, secp256k1_musig_partial_signature *partial_sig_other, unsigned char *msg, unsigned char *sk, unsigned char *session_id, secp256k1_musig_partial_signature *partial_sig, int do_combine) {
+    secp256k1_musig_session session;
+    secp256k1_musig_session_signer_data signers[2];
+    unsigned char nonce_commitment[32];
+    const unsigned char *ncs[2];
+    secp256k1_pubkey nonce;
+    secp256k1_musig_partial_signature partial_sigs[2];
+    secp256k1_schnorrsig sig;
+    int partial_verify, sig_combine;
+
+    CHECK(secp256k1_musig_session_initialize(ctx, &session, signers, nonce_commitment, session_id, msg, combined_pk, pk_hash, 2, 0, sk) == 1);
+    ncs[0] = nonce_commitment_other;
+    ncs[1] = nonce_commitment;
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session, signers, &nonce, ncs, 2) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[0], nonce_other) == 1);
+    CHECK(secp256k1_musig_set_nonce(ctx, &signers[1], &nonce) == 1);
+
+    partial_sigs[0] = *partial_sig_other;
+    partial_sigs[1] = *partial_sig;
+    if (do_combine != 0) {
+        CHECK(secp256k1_musig_session_combine_nonces(ctx, &session, signers, 2, NULL, NULL) == 1);
+    }
+    partial_verify = secp256k1_musig_partial_sig_verify(ctx, &session, signers, partial_sig_other, &pks[0]);
+    sig_combine = secp256k1_musig_partial_sig_combine(ctx, &session, &sig, partial_sigs, 2);
+    if (do_combine != 0) {
+        /* Return 1 if both succeeded */
+        return partial_verify && sig_combine;
+    }
+    /* Return 0 if both failed */
+    return partial_verify || sig_combine;
+}
+
+void musig_state_machine_tests(secp256k1_scratch_space *scratch) {
+    size_t i;
+    secp256k1_musig_session session[2];
+    secp256k1_musig_session_signer_data signers0[2];
+    secp256k1_musig_session_signer_data signers1[2];
+    unsigned char nonce_commitment[2][32];
+    unsigned char session_id[2][32];
+    unsigned char msg[32];
+    unsigned char sk[2][32];
+    secp256k1_pubkey pk[2];
+    secp256k1_pubkey combined_pk;
+    unsigned char pk_hash[32];
+    secp256k1_pubkey nonce[2];
+    const unsigned char *ncs[2];
+    secp256k1_musig_partial_signature partial_sig[2];
+    unsigned char msghash1[32];
+    unsigned char msghash2[32];
+
+    /* Run state machine with the same objects twice to test that it's allowed to
+     * reinitialize session and session_signer_data. */
+    for (i = 0; i < 2; i++) {
+        /* Setup */
+        secp256k1_rand256(session_id[0]);
+        secp256k1_rand256(session_id[1]);
+        secp256k1_rand256(sk[0]);
+        secp256k1_rand256(sk[1]);
+        secp256k1_rand256(msg);
+        CHECK(secp256k1_ec_pubkey_create(ctx, &pk[0], sk[0]) == 1);
+        CHECK(secp256k1_ec_pubkey_create(ctx, &pk[1], sk[1]) == 1);
+        CHECK(secp256k1_musig_pubkey_combine(ctx, scratch, &combined_pk, pk_hash, pk, 2) == 1);
+        CHECK(secp256k1_musig_session_initialize(ctx, &session[0], signers0, nonce_commitment[0], session_id[0], msg, &combined_pk, pk_hash, 2, 0, sk[0]) == 1);
+        CHECK(secp256k1_musig_session_initialize(ctx, &session[1], signers1, nonce_commitment[1], session_id[1], msg, &combined_pk, pk_hash, 2, 1, sk[1]) == 1);
+
+        /* Set nonce commitments */
+        ncs[0] = nonce_commitment[0];
+        ncs[1] = nonce_commitment[1];
+        CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session[0], signers0, &nonce[0], ncs, 2) == 1);
+        /* Changing a nonce commitment is not okay */
+        ncs[1] = (unsigned char*) "this isn't a nonce commitment...";
+        CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session[0], signers0, &nonce[0], ncs, 2) == 0);
+        /* Repeating with the same nonce commitments is okay */
+        ncs[1] = nonce_commitment[1];
+        CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session[0], signers0, &nonce[0], ncs, 2) == 1);
+
+        /* Get nonce for signer 1 */
+        CHECK(secp256k1_musig_session_get_public_nonce(ctx, &session[1], signers1, &nonce[1], ncs, 2) == 1);
+
+        /* Set nonces */
+        CHECK(secp256k1_musig_set_nonce(ctx, &signers0[0], &nonce[0]) == 1);
+        /* Can't set nonce that doesn't match nonce commitment */
+        CHECK(secp256k1_musig_set_nonce(ctx, &signers0[1], &nonce[0]) == 0);
+        /* Set correct nonce */
+        CHECK(secp256k1_musig_set_nonce(ctx, &signers0[1], &nonce[1]) == 1);
+
+        /* Combine nonces */
+        CHECK(secp256k1_musig_session_combine_nonces(ctx, &session[0], signers0, 2, NULL, NULL) == 1);
+        /* Not everyone is present from signer 1's view */
+        CHECK(secp256k1_musig_session_combine_nonces(ctx, &session[1], signers1, 2, NULL, NULL) == 0);
+        /* Make everyone present */
+        CHECK(secp256k1_musig_set_nonce(ctx, &signers1[0], &nonce[0]) == 1);
+        CHECK(secp256k1_musig_set_nonce(ctx, &signers1[1], &nonce[1]) == 1);
+
+        /* Can't combine nonces from signers of a different session */
+        CHECK(musig_state_machine_diff_signers_combine_nonce_test(&combined_pk, pk_hash, nonce_commitment[0], &nonce[0], msg, sk[1], signers1, 1) == 0);
+        CHECK(musig_state_machine_diff_signers_combine_nonce_test(&combined_pk, pk_hash, nonce_commitment[0], &nonce[0], msg, sk[1], signers1, 0) == 1);
+
+        /* Partially sign */
+        CHECK(secp256k1_musig_partial_sign(ctx, &session[0], &partial_sig[0]) == 1);
+        /* Can't verify or sign until nonce is combined */
+        CHECK(secp256k1_musig_partial_sig_verify(ctx, &session[1], &signers1[0], &partial_sig[0], &pk[0]) == 0);
+        CHECK(secp256k1_musig_partial_sign(ctx, &session[1], &partial_sig[1]) == 0);
+        CHECK(secp256k1_musig_session_combine_nonces(ctx, &session[1], signers1, 2, NULL, NULL) == 1);
+        CHECK(secp256k1_musig_partial_sig_verify(ctx, &session[1], &signers1[0], &partial_sig[0], &pk[0]) == 1);
+        /* messagehash should be the same as a session whose get_public_nonce was called
+         * with different signers (i.e. they diff in public keys). This is because the
+         * public keys of the signers is set in stone when initializing the session. */
+        CHECK(secp256k1_musig_compute_messagehash(ctx, msghash1, &session[1]) == 1);
+        CHECK(musig_state_machine_diff_signer_msghash_test(msghash2, pk, &combined_pk, pk_hash, ncs, msg, &nonce[0], sk[1], session_id[1]) == 1);
+        CHECK(memcmp(msghash1, msghash2, 32) == 0);
+        CHECK(secp256k1_musig_partial_sign(ctx, &session[1], &partial_sig[1]) == 1);
+        CHECK(secp256k1_musig_partial_sig_verify(ctx, &session[1], &signers1[1], &partial_sig[1], &pk[1]) == 1);
+        /* Wrong signature */
+        CHECK(secp256k1_musig_partial_sig_verify(ctx, &session[1], &signers1[1], &partial_sig[0], &pk[1]) == 0);
+        /* Can't sign or verify until msg is set */
+        CHECK(musig_state_machine_missing_msg_test(pk, &combined_pk, pk_hash, nonce_commitment[0], &nonce[0], &partial_sig[0], sk[1], session_id[1], NULL) == 0);
+        CHECK(musig_state_machine_missing_msg_test(pk, &combined_pk, pk_hash, nonce_commitment[0], &nonce[0], &partial_sig[0], sk[1], session_id[1], msg) == 1);
+
+        /* Can't verify and combine partial sigs until nonces are combined */
+        CHECK(musig_state_machine_missing_combine_test(pk, &combined_pk, pk_hash, nonce_commitment[0], &nonce[0], &partial_sig[0], msg, sk[1], session_id[1], &partial_sig[1], 0) == 0);
+        CHECK(musig_state_machine_missing_combine_test(pk, &combined_pk, pk_hash, nonce_commitment[0], &nonce[0], &partial_sig[0], msg, sk[1], session_id[1], &partial_sig[1], 1) == 1);
+    }
+}
+
+void scriptless_atomic_swap(secp256k1_scratch_space *scratch) {
+    /* Throughout this test "a" and "b" refer to two hypothetical blockchains,
+     * while the indices 0 and 1 refer to the two signers. Here signer 0 is
+     * sending a-coins to signer 1, while signer 1 is sending b-coins to signer
+     * 0. Signer 0 produces the adaptor signatures. */
+    secp256k1_schnorrsig final_sig_a;
+    secp256k1_schnorrsig final_sig_b;
+    secp256k1_musig_partial_signature partial_sig_a[2];
+    secp256k1_musig_partial_signature partial_sig_b_adapted[2];
+    secp256k1_musig_partial_signature partial_sig_b[2];
+    unsigned char sec_adaptor[32];
+    unsigned char sec_adaptor_extracted[32];
+    secp256k1_pubkey pub_adaptor;
+
+    unsigned char seckey_a[2][32];
+    unsigned char seckey_b[2][32];
+    secp256k1_pubkey pk_a[2];
+    secp256k1_pubkey pk_b[2];
+    unsigned char pk_hash_a[32];
+    unsigned char pk_hash_b[32];
+    secp256k1_pubkey combined_pk_a;
+    secp256k1_pubkey combined_pk_b;
+    secp256k1_musig_session musig_session_a[2];
+    secp256k1_musig_session musig_session_b[2];
+    unsigned char noncommit_a[2][32];
+    unsigned char noncommit_b[2][32];
+    const unsigned char *noncommit_a_ptr[2];
+    const unsigned char *noncommit_b_ptr[2];
+    secp256k1_pubkey pubnon_a[2];
+    secp256k1_pubkey pubnon_b[2];
+    int nonce_is_negated_a;
+    int nonce_is_negated_b;
+    secp256k1_musig_session_signer_data data_a[2];
+    secp256k1_musig_session_signer_data data_b[2];
+
+    const unsigned char seed[32] = "still tired of choosing seeds...";
+    const unsigned char msg32_a[32] = "this is the message blockchain a";
+    const unsigned char msg32_b[32] = "this is the message blockchain b";
+
+    /* Step 1: key setup */
+    secp256k1_rand256(seckey_a[0]);
+    secp256k1_rand256(seckey_a[1]);
+    secp256k1_rand256(seckey_b[0]);
+    secp256k1_rand256(seckey_b[1]);
+    secp256k1_rand256(sec_adaptor);
+
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk_a[0], seckey_a[0]));
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk_a[1], seckey_a[1]));
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk_b[0], seckey_b[0]));
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk_b[1], seckey_b[1]));
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pub_adaptor, sec_adaptor));
+
+    CHECK(secp256k1_musig_pubkey_combine(ctx, scratch, &combined_pk_a, pk_hash_a, pk_a, 2));
+    CHECK(secp256k1_musig_pubkey_combine(ctx, scratch, &combined_pk_b, pk_hash_b, pk_b, 2));
+
+    CHECK(secp256k1_musig_session_initialize(ctx, &musig_session_a[0], data_a, noncommit_a[0], seed, msg32_a, &combined_pk_a, pk_hash_a, 2, 0, seckey_a[0]));
+    CHECK(secp256k1_musig_session_initialize(ctx, &musig_session_a[1], data_a, noncommit_a[1], seed, msg32_a, &combined_pk_a, pk_hash_a, 2, 1, seckey_a[1]));
+    noncommit_a_ptr[0] = noncommit_a[0];
+    noncommit_a_ptr[1] = noncommit_a[1];
+
+    CHECK(secp256k1_musig_session_initialize(ctx, &musig_session_b[0], data_b, noncommit_b[0], seed, msg32_b, &combined_pk_b, pk_hash_b, 2, 0, seckey_b[0]));
+    CHECK(secp256k1_musig_session_initialize(ctx, &musig_session_b[1], data_b, noncommit_b[1], seed, msg32_b, &combined_pk_b, pk_hash_b, 2, 1, seckey_b[1]));
+    noncommit_b_ptr[0] = noncommit_b[0];
+    noncommit_b_ptr[1] = noncommit_b[1];
+
+    /* Step 2: Exchange nonces */
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &musig_session_a[0], data_a, &pubnon_a[0], noncommit_a_ptr, 2));
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &musig_session_a[1], data_a, &pubnon_a[1], noncommit_a_ptr, 2));
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &musig_session_b[0], data_b, &pubnon_b[0], noncommit_b_ptr, 2));
+    CHECK(secp256k1_musig_session_get_public_nonce(ctx, &musig_session_b[1], data_b, &pubnon_b[1], noncommit_b_ptr, 2));
+    CHECK(secp256k1_musig_set_nonce(ctx, &data_a[0], &pubnon_a[0]));
+    CHECK(secp256k1_musig_set_nonce(ctx, &data_a[1], &pubnon_a[1]));
+    CHECK(secp256k1_musig_set_nonce(ctx, &data_b[0], &pubnon_b[0]));
+    CHECK(secp256k1_musig_set_nonce(ctx, &data_b[1], &pubnon_b[1]));
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &musig_session_a[0], data_a, 2, &nonce_is_negated_a, &pub_adaptor));
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &musig_session_a[1], data_a, 2, NULL, &pub_adaptor));
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &musig_session_b[0], data_b, 2, &nonce_is_negated_b, &pub_adaptor));
+    CHECK(secp256k1_musig_session_combine_nonces(ctx, &musig_session_b[1], data_b, 2, NULL, &pub_adaptor));
+
+    /* Step 3: Signer 0 produces partial signatures for both chains. */
+    CHECK(secp256k1_musig_partial_sign(ctx, &musig_session_a[0], &partial_sig_a[0]));
+    CHECK(secp256k1_musig_partial_sign(ctx, &musig_session_b[0], &partial_sig_b[0]));
+
+    /* Step 4: Signer 1 receives partial signatures, verifies them and creates a
+     * partial signature to send B-coins to signer 0. */
+    CHECK(secp256k1_musig_partial_sig_verify(ctx, &musig_session_a[1], data_a, &partial_sig_a[0], &pk_a[0]) == 1);
+    CHECK(secp256k1_musig_partial_sig_verify(ctx, &musig_session_b[1], data_b, &partial_sig_b[0], &pk_b[0]) == 1);
+    CHECK(secp256k1_musig_partial_sign(ctx, &musig_session_b[1], &partial_sig_b[1]));
+
+    /* Step 5: Signer 0 adapts its own partial signature and combines it with the
+     * partial signature from signer 1. This results in a complete signature which
+     * is broadcasted by signer 0 to take B-coins. */
+    CHECK(secp256k1_musig_partial_sig_adapt(ctx, &partial_sig_b_adapted[0], &partial_sig_b[0], sec_adaptor, nonce_is_negated_b));
+    memcpy(&partial_sig_b_adapted[1], &partial_sig_b[1], sizeof(partial_sig_b_adapted[1]));
+    CHECK(secp256k1_musig_partial_sig_combine(ctx, &musig_session_b[0], &final_sig_b, partial_sig_b_adapted, 2) == 1);
+    CHECK(secp256k1_schnorrsig_verify(ctx, &final_sig_b, msg32_b, &combined_pk_b) == 1);
+
+    /* Step 6: Signer 1 extracts adaptor from the published signature, applies it to
+     * other partial signature, and takes A-coins. */
+    CHECK(secp256k1_musig_extract_secret_adaptor(ctx, sec_adaptor_extracted, &final_sig_b, partial_sig_b, 2, nonce_is_negated_b) == 1);
+    CHECK(memcmp(sec_adaptor_extracted, sec_adaptor, sizeof(sec_adaptor)) == 0); /* in real life we couldn't check this, of course */
+    CHECK(secp256k1_musig_partial_sig_adapt(ctx, &partial_sig_a[0], &partial_sig_a[0], sec_adaptor_extracted, nonce_is_negated_a));
+    CHECK(secp256k1_musig_partial_sign(ctx, &musig_session_a[1], &partial_sig_a[1]));
+    CHECK(secp256k1_musig_partial_sig_combine(ctx, &musig_session_a[1], &final_sig_a, partial_sig_a, 2) == 1);
+    CHECK(secp256k1_schnorrsig_verify(ctx, &final_sig_a, msg32_a, &combined_pk_a) == 1);
+}
+
+/* Checks that hash initialized by secp256k1_musig_sha256_init_tagged has the
+ * expected state. */
+void sha256_tag_test(void) {
+    char tag[17] = "MuSig coefficient";
+    secp256k1_sha256 sha;
+    secp256k1_sha256 sha_tagged;
+    unsigned char buf[32];
+    unsigned char buf2[32];
+    size_t i;
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, (unsigned char *) tag, 17);
+    secp256k1_sha256_finalize(&sha, buf);
+    /* buf = SHA256("MuSig coefficient") */
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, buf, 32);
+    secp256k1_sha256_write(&sha, buf, 32);
+    /* Is buffer fully consumed? */
+    CHECK((sha.bytes & 0x3F) == 0);
+
+    /* Compare with tagged SHA */
+    secp256k1_musig_sha256_init_tagged(&sha_tagged);
+    for (i = 0; i < 8; i++) {
+        CHECK(sha_tagged.s[i] == sha.s[i]);
+    }
+    secp256k1_sha256_write(&sha, buf, 32);
+    secp256k1_sha256_write(&sha_tagged, buf, 32);
+    secp256k1_sha256_finalize(&sha, buf);
+    secp256k1_sha256_finalize(&sha_tagged, buf2);
+    CHECK(memcmp(buf, buf2, 32) == 0);
+}
+
+void run_musig_tests(void) {
+    int i;
+    secp256k1_scratch_space *scratch = secp256k1_scratch_space_create(ctx, 1024 * 1024);
+
+    musig_api_tests(scratch);
+    musig_state_machine_tests(scratch);
+    for (i = 0; i < count; i++) {
+        /* Run multiple times to ensure that the nonce is negated in some tests */
+        scriptless_atomic_swap(scratch);
+    }
+    sha256_tag_test();
+
+    secp256k1_scratch_space_destroy(scratch);
+}
+
+#endif

src/modules/rangeproof/Makefile.am.include

@@ -0,0 +1,15 @@
+include_HEADERS += include/secp256k1_rangeproof.h
+noinst_HEADERS += src/modules/rangeproof/main_impl.h
+noinst_HEADERS += src/modules/rangeproof/pedersen.h
+noinst_HEADERS += src/modules/rangeproof/pedersen_impl.h
+noinst_HEADERS += src/modules/rangeproof/borromean.h
+noinst_HEADERS += src/modules/rangeproof/borromean_impl.h
+noinst_HEADERS += src/modules/rangeproof/rangeproof.h
+noinst_HEADERS += src/modules/rangeproof/rangeproof_impl.h
+noinst_HEADERS += src/modules/rangeproof/tests_impl.h
+if USE_BENCHMARK
+noinst_PROGRAMS += bench_rangeproof
+bench_rangeproof_SOURCES = src/bench_rangeproof.c
+bench_rangeproof_LDADD = libsecp256k1.la $(SECP_LIBS)
+bench_rangeproof_LDFLAGS = -static
+endif

src/modules/rangeproof/borromean.h

@@ -0,0 +1,24 @@
+/**********************************************************************
+ * Copyright (c) 2014, 2015 Gregory Maxwell                          *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+
+#ifndef _SECP256K1_BORROMEAN_H_
+#define _SECP256K1_BORROMEAN_H_
+
+#include "scalar.h"
+#include "field.h"
+#include "group.h"
+#include "ecmult.h"
+#include "ecmult_gen.h"
+
+int secp256k1_borromean_verify(const secp256k1_ecmult_context* ecmult_ctx, secp256k1_scalar *evalues, const unsigned char *e0, const secp256k1_scalar *s,
+ const secp256k1_gej *pubs, const size_t *rsizes, size_t nrings, const unsigned char *m, size_t mlen);
+
+int secp256k1_borromean_sign(const secp256k1_ecmult_context* ecmult_ctx, const secp256k1_ecmult_gen_context *ecmult_gen_ctx,
+ unsigned char *e0, secp256k1_scalar *s, const secp256k1_gej *pubs, const secp256k1_scalar *k, const secp256k1_scalar *sec,
+ const size_t *rsizes, const size_t *secidx, size_t nrings, const unsigned char *m, size_t mlen);
+
+#endif

src/modules/rangeproof/borromean_impl.h

@@ -0,0 +1,204 @@
+/**********************************************************************
+ * Copyright (c) 2014, 2015 Gregory Maxwell                          *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+
+#ifndef _SECP256K1_BORROMEAN_IMPL_H_
+#define _SECP256K1_BORROMEAN_IMPL_H_
+
+#include "scalar.h"
+#include "field.h"
+#include "group.h"
+#include "hash.h"
+#include "eckey.h"
+#include "ecmult.h"
+#include "ecmult_gen.h"
+#include "borromean.h"
+
+#include <limits.h>
+#include <string.h>
+
+#ifdef WORDS_BIGENDIAN
+#define BE32(x) (x)
+#else
+#define BE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
+#endif
+
+SECP256K1_INLINE static void secp256k1_borromean_hash(unsigned char *hash, const unsigned char *m, size_t mlen, const unsigned char *e, size_t elen,
+ size_t ridx, size_t eidx) {
+    uint32_t ring;
+    uint32_t epos;
+    secp256k1_sha256 sha256_en;
+    secp256k1_sha256_initialize(&sha256_en);
+    ring = BE32((uint32_t)ridx);
+    epos = BE32((uint32_t)eidx);
+    secp256k1_sha256_write(&sha256_en, e, elen);
+    secp256k1_sha256_write(&sha256_en, m, mlen);
+    secp256k1_sha256_write(&sha256_en, (unsigned char*)&ring, 4);
+    secp256k1_sha256_write(&sha256_en, (unsigned char*)&epos, 4);
+    secp256k1_sha256_finalize(&sha256_en, hash);
+}
+
+/**  "Borromean" ring signature.
+ *   Verifies nrings concurrent ring signatures all sharing a challenge value.
+ *   Signature is one s value per pubkey and a hash.
+ *   Verification equation:
+ *   | m = H(P_{0..}||message) (Message must contain pubkeys or a pubkey commitment)
+ *   | For each ring i:
+ *   | | en = to_scalar(H(e0||m||i||0))
+ *   | | For each pubkey j:
+ *   | | | r = s_i_j G + en * P_i_j
+ *   | | | e = H(r||m||i||j)
+ *   | | | en = to_scalar(e)
+ *   | | r_i = r
+ *   | return e_0 ==== H(r_{0..i}||m)
+ */
+int secp256k1_borromean_verify(const secp256k1_ecmult_context* ecmult_ctx, secp256k1_scalar *evalues, const unsigned char *e0,
+ const secp256k1_scalar *s, const secp256k1_gej *pubs, const size_t *rsizes, size_t nrings, const unsigned char *m, size_t mlen) {
+    secp256k1_gej rgej;
+    secp256k1_ge rge;
+    secp256k1_scalar ens;
+    secp256k1_sha256 sha256_e0;
+    unsigned char tmp[33];
+    size_t i;
+    size_t j;
+    size_t count;
+    size_t size;
+    int overflow;
+    VERIFY_CHECK(ecmult_ctx != NULL);
+    VERIFY_CHECK(e0 != NULL);
+    VERIFY_CHECK(s != NULL);
+    VERIFY_CHECK(pubs != NULL);
+    VERIFY_CHECK(rsizes != NULL);
+    VERIFY_CHECK(nrings > 0);
+    VERIFY_CHECK(m != NULL);
+    count = 0;
+    secp256k1_sha256_initialize(&sha256_e0);
+    for (i = 0; i < nrings; i++) {
+        VERIFY_CHECK(INT_MAX - count > rsizes[i]);
+        secp256k1_borromean_hash(tmp, m, mlen, e0, 32, i, 0);
+        secp256k1_scalar_set_b32(&ens, tmp, &overflow);
+        for (j = 0; j < rsizes[i]; j++) {
+            if (overflow || secp256k1_scalar_is_zero(&s[count]) || secp256k1_scalar_is_zero(&ens) || secp256k1_gej_is_infinity(&pubs[count])) {
+                return 0;
+            }
+            if (evalues) {
+                /*If requested, save the challenges for proof rewind.*/
+                evalues[count] = ens;
+            }
+            secp256k1_ecmult(ecmult_ctx, &rgej, &pubs[count], &ens, &s[count]);
+            if (secp256k1_gej_is_infinity(&rgej)) {
+                return 0;
+            }
+            /* OPT: loop can be hoisted and split to use batch inversion across all the rings; this would make it much faster. */
+            secp256k1_ge_set_gej_var(&rge, &rgej);
+            secp256k1_eckey_pubkey_serialize(&rge, tmp, &size, 1);
+            if (j != rsizes[i] - 1) {
+                secp256k1_borromean_hash(tmp, m, mlen, tmp, 33, i, j + 1);
+                secp256k1_scalar_set_b32(&ens, tmp, &overflow);
+            } else {
+                secp256k1_sha256_write(&sha256_e0, tmp, size);
+            }
+            count++;
+        }
+    }
+    secp256k1_sha256_write(&sha256_e0, m, mlen);
+    secp256k1_sha256_finalize(&sha256_e0, tmp);
+    return memcmp(e0, tmp, 32) == 0;
+}
+
+int secp256k1_borromean_sign(const secp256k1_ecmult_context* ecmult_ctx, const secp256k1_ecmult_gen_context *ecmult_gen_ctx,
+ unsigned char *e0, secp256k1_scalar *s, const secp256k1_gej *pubs, const secp256k1_scalar *k, const secp256k1_scalar *sec,
+ const size_t *rsizes, const size_t *secidx, size_t nrings, const unsigned char *m, size_t mlen) {
+    secp256k1_gej rgej;
+    secp256k1_ge rge;
+    secp256k1_scalar ens;
+    secp256k1_sha256 sha256_e0;
+    unsigned char tmp[33];
+    size_t i;
+    size_t j;
+    size_t count;
+    size_t size;
+    int overflow;
+    VERIFY_CHECK(ecmult_ctx != NULL);
+    VERIFY_CHECK(ecmult_gen_ctx != NULL);
+    VERIFY_CHECK(e0 != NULL);
+    VERIFY_CHECK(s != NULL);
+    VERIFY_CHECK(pubs != NULL);
+    VERIFY_CHECK(k != NULL);
+    VERIFY_CHECK(sec != NULL);
+    VERIFY_CHECK(rsizes != NULL);
+    VERIFY_CHECK(secidx != NULL);
+    VERIFY_CHECK(nrings > 0);
+    VERIFY_CHECK(m != NULL);
+    secp256k1_sha256_initialize(&sha256_e0);
+    count = 0;
+    for (i = 0; i < nrings; i++) {
+        VERIFY_CHECK(INT_MAX - count > rsizes[i]);
+        secp256k1_ecmult_gen(ecmult_gen_ctx, &rgej, &k[i]);
+        secp256k1_ge_set_gej(&rge, &rgej);
+        if (secp256k1_gej_is_infinity(&rgej)) {
+            return 0;
+        }
+        secp256k1_eckey_pubkey_serialize(&rge, tmp, &size, 1);
+        for (j = secidx[i] + 1; j < rsizes[i]; j++) {
+            secp256k1_borromean_hash(tmp, m, mlen, tmp, 33, i, j);
+            secp256k1_scalar_set_b32(&ens, tmp, &overflow);
+            if (overflow || secp256k1_scalar_is_zero(&ens)) {
+                return 0;
+            }
+            /** The signing algorithm as a whole is not memory uniform so there is likely a cache sidechannel that
+             *  leaks which members are non-forgeries. That the forgeries themselves are variable time may leave
+             *  an additional privacy impacting timing side-channel, but not a key loss one.
+             */
+            secp256k1_ecmult(ecmult_ctx, &rgej, &pubs[count + j], &ens, &s[count + j]);
+            if (secp256k1_gej_is_infinity(&rgej)) {
+                return 0;
+            }
+            secp256k1_ge_set_gej_var(&rge, &rgej);
+            secp256k1_eckey_pubkey_serialize(&rge, tmp, &size, 1);
+        }
+        secp256k1_sha256_write(&sha256_e0, tmp, size);
+        count += rsizes[i];
+    }
+    secp256k1_sha256_write(&sha256_e0, m, mlen);
+    secp256k1_sha256_finalize(&sha256_e0, e0);
+    count = 0;
+    for (i = 0; i < nrings; i++) {
+        VERIFY_CHECK(INT_MAX - count > rsizes[i]);
+        secp256k1_borromean_hash(tmp, m, mlen, e0, 32, i, 0);
+        secp256k1_scalar_set_b32(&ens, tmp, &overflow);
+        if (overflow || secp256k1_scalar_is_zero(&ens)) {
+            return 0;
+        }
+        for (j = 0; j < secidx[i]; j++) {
+            secp256k1_ecmult(ecmult_ctx, &rgej, &pubs[count + j], &ens, &s[count + j]);
+            if (secp256k1_gej_is_infinity(&rgej)) {
+                return 0;
+            }
+            secp256k1_ge_set_gej_var(&rge, &rgej);
+            secp256k1_eckey_pubkey_serialize(&rge, tmp, &size, 1);
+            secp256k1_borromean_hash(tmp, m, mlen, tmp, 33, i, j + 1);
+            secp256k1_scalar_set_b32(&ens, tmp, &overflow);
+            if (overflow || secp256k1_scalar_is_zero(&ens)) {
+                return 0;
+            }
+        }
+        secp256k1_scalar_mul(&s[count + j], &ens, &sec[i]);
+        secp256k1_scalar_negate(&s[count + j], &s[count + j]);
+        secp256k1_scalar_add(&s[count + j], &s[count + j], &k[i]);
+        if (secp256k1_scalar_is_zero(&s[count + j])) {
+            return 0;
+        }
+        count += rsizes[i];
+    }
+    secp256k1_scalar_clear(&ens);
+    secp256k1_ge_clear(&rge);
+    secp256k1_gej_clear(&rgej);
+    memset(tmp, 0, 33);
+    return 1;
+}
+
+#endif

src/modules/rangeproof/main_impl.h

@@ -0,0 +1,300 @@
+/**********************************************************************
+ * Copyright (c) 2014-2015 Gregory Maxwell                            *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_RANGEPROOF_MAIN
+#define SECP256K1_MODULE_RANGEPROOF_MAIN
+
+#include "group.h"
+
+#include "modules/rangeproof/pedersen_impl.h"
+#include "modules/rangeproof/borromean_impl.h"
+#include "modules/rangeproof/rangeproof_impl.h"
+
+/** Alternative generator for secp256k1.
+ *  This is the sha256 of 'g' after DER encoding (without compression),
+ *  which happens to be a point on the curve. More precisely, the generator is
+ *  derived by running the following script with the sage mathematics software.
+
+    import hashlib
+    F = FiniteField (0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F)
+    G_DER = '0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8'
+    G2 = EllipticCurve ([F (0), F (7)]).lift_x(F(int(hashlib.sha256(G_DER.decode('hex')).hexdigest(),16)))
+    print('%x %x' % G2.xy())
+ */
+static const secp256k1_generator secp256k1_generator_h_internal = {{
+    0x50, 0x92, 0x9b, 0x74, 0xc1, 0xa0, 0x49, 0x54, 0xb7, 0x8b, 0x4b, 0x60, 0x35, 0xe9, 0x7a, 0x5e,
+    0x07, 0x8a, 0x5a, 0x0f, 0x28, 0xec, 0x96, 0xd5, 0x47, 0xbf, 0xee, 0x9a, 0xce, 0x80, 0x3a, 0xc0,
+    0x31, 0xd3, 0xc6, 0x86, 0x39, 0x73, 0x92, 0x6e, 0x04, 0x9e, 0x63, 0x7c, 0xb1, 0xb5, 0xf4, 0x0a,
+    0x36, 0xda, 0xc2, 0x8a, 0xf1, 0x76, 0x69, 0x68, 0xc3, 0x0c, 0x23, 0x13, 0xf3, 0xa3, 0x89, 0x04
+}};
+
+const secp256k1_generator *secp256k1_generator_h = &secp256k1_generator_h_internal;
+
+static void secp256k1_pedersen_commitment_load(secp256k1_ge* ge, const secp256k1_pedersen_commitment* commit) {
+    secp256k1_fe fe;
+    secp256k1_fe_set_b32(&fe, &commit->data[1]);
+    secp256k1_ge_set_xquad(ge, &fe);
+    if (commit->data[0] & 1) {
+        secp256k1_ge_neg(ge, ge);
+    }
+}
+
+static void secp256k1_pedersen_commitment_save(secp256k1_pedersen_commitment* commit, secp256k1_ge* ge) {
+    secp256k1_fe_normalize(&ge->x);
+    secp256k1_fe_get_b32(&commit->data[1], &ge->x);
+    commit->data[0] = 9 ^ secp256k1_fe_is_quad_var(&ge->y);
+}
+
+int secp256k1_pedersen_commitment_parse(const secp256k1_context* ctx, secp256k1_pedersen_commitment* commit, const unsigned char *input) {
+    secp256k1_fe x;
+    secp256k1_ge ge;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(commit != NULL);
+    ARG_CHECK(input != NULL);
+    (void) ctx;
+
+    if ((input[0] & 0xFE) != 8 ||
+        !secp256k1_fe_set_b32(&x, &input[1]) ||
+        !secp256k1_ge_set_xquad(&ge, &x)) {
+        return 0;
+    }
+    if (input[0] & 1) {
+        secp256k1_ge_neg(&ge, &ge);
+    }
+    secp256k1_pedersen_commitment_save(commit, &ge);
+    return 1;
+}
+
+int secp256k1_pedersen_commitment_serialize(const secp256k1_context* ctx, unsigned char *output, const secp256k1_pedersen_commitment* commit) {
+    secp256k1_ge ge;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(output != NULL);
+    ARG_CHECK(commit != NULL);
+
+    secp256k1_pedersen_commitment_load(&ge, commit);
+
+    output[0] = 9 ^ secp256k1_fe_is_quad_var(&ge.y);
+    secp256k1_fe_normalize_var(&ge.x);
+    secp256k1_fe_get_b32(&output[1], &ge.x);
+    return 1;
+}
+
+/* Generates a pedersen commitment: *commit = blind * G + value * G2. The blinding factor is 32 bytes.*/
+int secp256k1_pedersen_commit(const secp256k1_context* ctx, secp256k1_pedersen_commitment *commit, const unsigned char *blind, uint64_t value, const secp256k1_generator* gen) {
+    secp256k1_ge genp;
+    secp256k1_gej rj;
+    secp256k1_ge r;
+    secp256k1_scalar sec;
+    int overflow;
+    int ret = 0;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    ARG_CHECK(commit != NULL);
+    ARG_CHECK(blind != NULL);
+    ARG_CHECK(gen != NULL);
+    secp256k1_generator_load(&genp, gen);
+    secp256k1_scalar_set_b32(&sec, blind, &overflow);
+    if (!overflow) {
+        secp256k1_pedersen_ecmult(&ctx->ecmult_gen_ctx, &rj, &sec, value, &genp);
+        if (!secp256k1_gej_is_infinity(&rj)) {
+            secp256k1_ge_set_gej(&r, &rj);
+            secp256k1_pedersen_commitment_save(commit, &r);
+            ret = 1;
+        }
+        secp256k1_gej_clear(&rj);
+        secp256k1_ge_clear(&r);
+    }
+    secp256k1_scalar_clear(&sec);
+    return ret;
+}
+
+/** Takes a list of n pointers to 32 byte blinding values, the first negs of which are treated with positive sign and the rest
+ *  negative, then calculates an additional blinding value that adds to zero.
+ */
+int secp256k1_pedersen_blind_sum(const secp256k1_context* ctx, unsigned char *blind_out, const unsigned char * const *blinds, size_t n, size_t npositive) {
+    secp256k1_scalar acc;
+    secp256k1_scalar x;
+    size_t i;
+    int overflow;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(blind_out != NULL);
+    ARG_CHECK(blinds != NULL);
+    ARG_CHECK(npositive <= n);
+    (void) ctx;
+    secp256k1_scalar_set_int(&acc, 0);
+    for (i = 0; i < n; i++) {
+        secp256k1_scalar_set_b32(&x, blinds[i], &overflow);
+        if (overflow) {
+            return 0;
+        }
+        if (i >= npositive) {
+            secp256k1_scalar_negate(&x, &x);
+        }
+        secp256k1_scalar_add(&acc, &acc, &x);
+    }
+    secp256k1_scalar_get_b32(blind_out, &acc);
+    secp256k1_scalar_clear(&acc);
+    secp256k1_scalar_clear(&x);
+    return 1;
+}
+
+/* Takes two lists of commitments and sums the first set and subtracts the second and verifies that they sum to excess. */
+int secp256k1_pedersen_verify_tally(const secp256k1_context* ctx, const secp256k1_pedersen_commitment * const* commits, size_t pcnt, const secp256k1_pedersen_commitment * const* ncommits, size_t ncnt) {
+    secp256k1_gej accj;
+    secp256k1_ge add;
+    size_t i;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(!pcnt || (commits != NULL));
+    ARG_CHECK(!ncnt || (ncommits != NULL));
+    (void) ctx;
+    secp256k1_gej_set_infinity(&accj);
+    for (i = 0; i < ncnt; i++) {
+        secp256k1_pedersen_commitment_load(&add, ncommits[i]);
+        secp256k1_gej_add_ge_var(&accj, &accj, &add, NULL);
+    }
+    secp256k1_gej_neg(&accj, &accj);
+    for (i = 0; i < pcnt; i++) {
+        secp256k1_pedersen_commitment_load(&add, commits[i]);
+        secp256k1_gej_add_ge_var(&accj, &accj, &add, NULL);
+    }
+    return secp256k1_gej_is_infinity(&accj);
+}
+
+int secp256k1_pedersen_blind_generator_blind_sum(const secp256k1_context* ctx, const uint64_t *value, const unsigned char* const* generator_blind, unsigned char* const* blinding_factor, size_t n_total, size_t n_inputs) {
+    secp256k1_scalar sum;
+    secp256k1_scalar tmp;
+    size_t i;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(n_total == 0 || value != NULL);
+    ARG_CHECK(n_total == 0 || generator_blind != NULL);
+    ARG_CHECK(n_total == 0 || blinding_factor != NULL);
+    ARG_CHECK(n_total > n_inputs);
+    (void) ctx;
+
+    if (n_total == 0) {
+        return 1;
+    }
+
+    secp256k1_scalar_set_int(&sum, 0);
+    for (i = 0; i < n_total; i++) {
+        int overflow = 0;
+        secp256k1_scalar addend;
+        secp256k1_scalar_set_u64(&addend, value[i]);  /* s = v */
+
+        secp256k1_scalar_set_b32(&tmp, generator_blind[i], &overflow);
+        if (overflow == 1) {
+            secp256k1_scalar_clear(&tmp);
+            secp256k1_scalar_clear(&addend);
+            secp256k1_scalar_clear(&sum);
+            return 0;
+        }
+        secp256k1_scalar_mul(&addend, &addend, &tmp); /* s = vr */
+
+        secp256k1_scalar_set_b32(&tmp, blinding_factor[i], &overflow);
+        if (overflow == 1) {
+            secp256k1_scalar_clear(&tmp);
+            secp256k1_scalar_clear(&addend);
+            secp256k1_scalar_clear(&sum);
+            return 0;
+        }
+        secp256k1_scalar_add(&addend, &addend, &tmp); /* s = vr + r' */
+        secp256k1_scalar_cond_negate(&addend, i < n_inputs);  /* s is negated if it's an input */
+        secp256k1_scalar_add(&sum, &sum, &addend);    /* sum += s */
+        secp256k1_scalar_clear(&addend);
+    }
+
+    /* Right now tmp has the last pedersen blinding factor. Subtract the sum from it. */
+    secp256k1_scalar_negate(&sum, &sum);
+    secp256k1_scalar_add(&tmp, &tmp, &sum);
+    secp256k1_scalar_get_b32(blinding_factor[n_total - 1], &tmp);
+
+    secp256k1_scalar_clear(&tmp);
+    secp256k1_scalar_clear(&sum);
+    return 1;
+}
+
+int secp256k1_rangeproof_info(const secp256k1_context* ctx, int *exp, int *mantissa,
+ uint64_t *min_value, uint64_t *max_value, const unsigned char *proof, size_t plen) {
+    size_t offset;
+    uint64_t scale;
+    ARG_CHECK(exp != NULL);
+    ARG_CHECK(mantissa != NULL);
+    ARG_CHECK(min_value != NULL);
+    ARG_CHECK(max_value != NULL);
+    ARG_CHECK(proof != NULL);
+    offset = 0;
+    scale = 1;
+    (void)ctx;
+    return secp256k1_rangeproof_getheader_impl(&offset, exp, mantissa, &scale, min_value, max_value, proof, plen);
+}
+
+int secp256k1_rangeproof_rewind(const secp256k1_context* ctx,
+ unsigned char *blind_out, uint64_t *value_out, unsigned char *message_out, size_t *outlen, const unsigned char *nonce,
+ uint64_t *min_value, uint64_t *max_value,
+ const secp256k1_pedersen_commitment *commit, const unsigned char *proof, size_t plen, const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_generator* gen) {
+    secp256k1_ge commitp;
+    secp256k1_ge genp;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(commit != NULL);
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(min_value != NULL);
+    ARG_CHECK(max_value != NULL);
+    ARG_CHECK(message_out != NULL || outlen == NULL);
+    ARG_CHECK(nonce != NULL);
+    ARG_CHECK(extra_commit != NULL || extra_commit_len == 0);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    secp256k1_pedersen_commitment_load(&commitp, commit);
+    secp256k1_generator_load(&genp, gen);
+    return secp256k1_rangeproof_verify_impl(&ctx->ecmult_ctx, &ctx->ecmult_gen_ctx,
+     blind_out, value_out, message_out, outlen, nonce, min_value, max_value, &commitp, proof, plen, extra_commit, extra_commit_len, &genp);
+}
+
+int secp256k1_rangeproof_verify(const secp256k1_context* ctx, uint64_t *min_value, uint64_t *max_value,
+ const secp256k1_pedersen_commitment *commit, const unsigned char *proof, size_t plen, const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_generator* gen) {
+    secp256k1_ge commitp;
+    secp256k1_ge genp;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(commit != NULL);
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(min_value != NULL);
+    ARG_CHECK(max_value != NULL);
+    ARG_CHECK(extra_commit != NULL || extra_commit_len == 0);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    secp256k1_pedersen_commitment_load(&commitp, commit);
+    secp256k1_generator_load(&genp, gen);
+    return secp256k1_rangeproof_verify_impl(&ctx->ecmult_ctx, NULL,
+     NULL, NULL, NULL, NULL, NULL, min_value, max_value, &commitp, proof, plen, extra_commit, extra_commit_len, &genp);
+}
+
+int secp256k1_rangeproof_sign(const secp256k1_context* ctx, unsigned char *proof, size_t *plen, uint64_t min_value,
+ const secp256k1_pedersen_commitment *commit, const unsigned char *blind, const unsigned char *nonce, int exp, int min_bits, uint64_t value,
+ const unsigned char *message, size_t msg_len, const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_generator* gen){
+    secp256k1_ge commitp;
+    secp256k1_ge genp;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(plen != NULL);
+    ARG_CHECK(commit != NULL);
+    ARG_CHECK(blind != NULL);
+    ARG_CHECK(nonce != NULL);
+    ARG_CHECK(message != NULL || msg_len == 0);
+    ARG_CHECK(extra_commit != NULL || extra_commit_len == 0);
+    ARG_CHECK(gen != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    secp256k1_pedersen_commitment_load(&commitp, commit);
+    secp256k1_generator_load(&genp, gen);
+    return secp256k1_rangeproof_sign_impl(&ctx->ecmult_ctx, &ctx->ecmult_gen_ctx,
+     proof, plen, min_value, &commitp, blind, nonce, exp, min_bits, value, message, msg_len, extra_commit, extra_commit_len, &genp);
+}
+
+#endif

src/modules/rangeproof/pedersen.h

@@ -0,0 +1,22 @@
+/**********************************************************************
+ * Copyright (c) 2014, 2015 Gregory Maxwell                          *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_PEDERSEN_H_
+#define _SECP256K1_PEDERSEN_H_
+
+#include "ecmult_gen.h"
+#include "group.h"
+#include "scalar.h"
+
+#include <stdint.h>
+
+/** Multiply a small number with the generator: r = gn*G2 */
+static void secp256k1_pedersen_ecmult_small(secp256k1_gej *r, uint64_t gn, const secp256k1_ge* genp);
+
+/* sec * G + value * G2. */
+static void secp256k1_pedersen_ecmult(const secp256k1_ecmult_gen_context *ecmult_gen_ctx, secp256k1_gej *rj, const secp256k1_scalar *sec, uint64_t value, const secp256k1_ge* genp);
+
+#endif

src/modules/rangeproof/pedersen_impl.h

@@ -0,0 +1,51 @@
+/***********************************************************************
+ * Copyright (c) 2015 Gregory Maxwell                                  *
+ * Distributed under the MIT software license, see the accompanying    *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php. *
+ ***********************************************************************/
+
+#ifndef _SECP256K1_PEDERSEN_IMPL_H_
+#define _SECP256K1_PEDERSEN_IMPL_H_
+
+#include <string.h>
+
+#include "eckey.h"
+#include "ecmult_const.h"
+#include "ecmult_gen.h"
+#include "group.h"
+#include "field.h"
+#include "scalar.h"
+#include "util.h"
+
+static void secp256k1_pedersen_scalar_set_u64(secp256k1_scalar *sec, uint64_t value) {
+    unsigned char data[32];
+    int i;
+    for (i = 0; i < 24; i++) {
+        data[i] = 0;
+    }
+    for (; i < 32; i++) {
+        data[i] = value >> 56;
+        value <<= 8;
+    }
+    secp256k1_scalar_set_b32(sec, data, NULL);
+    memset(data, 0, 32);
+}
+
+static void secp256k1_pedersen_ecmult_small(secp256k1_gej *r, uint64_t gn, const secp256k1_ge* genp) {
+    secp256k1_scalar s;
+    secp256k1_pedersen_scalar_set_u64(&s, gn);
+    secp256k1_ecmult_const(r, genp, &s, 64);
+    secp256k1_scalar_clear(&s);
+}
+
+/* sec * G + value * G2. */
+SECP256K1_INLINE static void secp256k1_pedersen_ecmult(const secp256k1_ecmult_gen_context *ecmult_gen_ctx, secp256k1_gej *rj, const secp256k1_scalar *sec, uint64_t value, const secp256k1_ge* genp) {
+    secp256k1_gej vj;
+    secp256k1_ecmult_gen(ecmult_gen_ctx, rj, sec);
+    secp256k1_pedersen_ecmult_small(&vj, value, genp);
+    /* FIXME: constant time. */
+    secp256k1_gej_add_var(rj, rj, &vj, NULL);
+    secp256k1_gej_clear(&vj);
+}
+
+#endif

src/modules/rangeproof/rangeproof.h

@@ -0,0 +1,21 @@
+/**********************************************************************
+ * Copyright (c) 2015 Gregory Maxwell                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_RANGEPROOF_H_
+#define _SECP256K1_RANGEPROOF_H_
+
+#include "scalar.h"
+#include "group.h"
+#include "ecmult.h"
+#include "ecmult_gen.h"
+
+static int secp256k1_rangeproof_verify_impl(const secp256k1_ecmult_context* ecmult_ctx,
+ const secp256k1_ecmult_gen_context* ecmult_gen_ctx,
+ unsigned char *blindout, uint64_t *value_out, unsigned char *message_out, size_t *outlen, const unsigned char *nonce,
+ uint64_t *min_value, uint64_t *max_value, const secp256k1_ge *commit, const unsigned char *proof, size_t plen,
+ const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_ge* genp);
+
+#endif

src/modules/rangeproof/rangeproof_impl.h

@@ -0,0 +1,685 @@
+/**********************************************************************
+ * Copyright (c) 2015 Gregory Maxwell                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_RANGEPROOF_IMPL_H_
+#define _SECP256K1_RANGEPROOF_IMPL_H_
+
+#include "eckey.h"
+#include "scalar.h"
+#include "group.h"
+#include "rangeproof.h"
+#include "hash_impl.h"
+#include "pedersen_impl.h"
+#include "util.h"
+
+#include "modules/rangeproof/pedersen.h"
+#include "modules/rangeproof/borromean.h"
+
+SECP256K1_INLINE static void secp256k1_rangeproof_pub_expand(secp256k1_gej *pubs,
+ int exp, size_t *rsizes, size_t rings, const secp256k1_ge* genp) {
+    secp256k1_gej base;
+    size_t i;
+    size_t j;
+    size_t npub;
+    VERIFY_CHECK(exp < 19);
+    if (exp < 0) {
+        exp = 0;
+    }
+    secp256k1_gej_set_ge(&base, genp);
+    secp256k1_gej_neg(&base, &base);
+    while (exp--) {
+        /* Multiplication by 10 */
+        secp256k1_gej tmp;
+        secp256k1_gej_double_var(&tmp, &base, NULL);
+        secp256k1_gej_double_var(&base, &tmp, NULL);
+        secp256k1_gej_double_var(&base, &base, NULL);
+        secp256k1_gej_add_var(&base, &base, &tmp, NULL);
+    }
+    npub = 0;
+    for (i = 0; i < rings; i++) {
+        for (j = 1; j < rsizes[i]; j++) {
+            secp256k1_gej_add_var(&pubs[npub + j], &pubs[npub + j - 1], &base, NULL);
+        }
+        if (i < rings - 1) {
+            secp256k1_gej_double_var(&base, &base, NULL);
+            secp256k1_gej_double_var(&base, &base, NULL);
+        }
+        npub += rsizes[i];
+    }
+}
+
+SECP256K1_INLINE static void secp256k1_rangeproof_serialize_point(unsigned char* data, const secp256k1_ge *point) {
+    secp256k1_fe pointx;
+    pointx = point->x;
+    secp256k1_fe_normalize(&pointx);
+    data[0] = !secp256k1_fe_is_quad_var(&point->y);
+    secp256k1_fe_get_b32(data + 1, &pointx);
+}
+
+SECP256K1_INLINE static int secp256k1_rangeproof_genrand(secp256k1_scalar *sec, secp256k1_scalar *s, unsigned char *message,
+ size_t *rsizes, size_t rings, const unsigned char *nonce, const secp256k1_ge *commit, const unsigned char *proof, size_t len, const secp256k1_ge* genp) {
+    unsigned char tmp[32];
+    unsigned char rngseed[32 + 33 + 33 + 10];
+    secp256k1_rfc6979_hmac_sha256 rng;
+    secp256k1_scalar acc;
+    int overflow;
+    int ret;
+    size_t i;
+    size_t j;
+    int b;
+    size_t npub;
+    VERIFY_CHECK(len <= 10);
+    memcpy(rngseed, nonce, 32);
+    secp256k1_rangeproof_serialize_point(rngseed + 32, commit);
+    secp256k1_rangeproof_serialize_point(rngseed + 32 + 33, genp);
+    memcpy(rngseed + 33 + 33 + 32, proof, len);
+    secp256k1_rfc6979_hmac_sha256_initialize(&rng, rngseed, 32 + 33 + 33 + len);
+    secp256k1_scalar_clear(&acc);
+    npub = 0;
+    ret = 1;
+    for (i = 0; i < rings; i++) {
+        if (i < rings - 1) {
+            secp256k1_rfc6979_hmac_sha256_generate(&rng, tmp, 32);
+            do {
+                secp256k1_rfc6979_hmac_sha256_generate(&rng, tmp, 32);
+                secp256k1_scalar_set_b32(&sec[i], tmp, &overflow);
+            } while (overflow || secp256k1_scalar_is_zero(&sec[i]));
+            secp256k1_scalar_add(&acc, &acc, &sec[i]);
+        } else {
+            secp256k1_scalar_negate(&acc, &acc);
+            sec[i] = acc;
+        }
+        for (j = 0; j < rsizes[i]; j++) {
+            secp256k1_rfc6979_hmac_sha256_generate(&rng, tmp, 32);
+            if (message) {
+                for (b = 0; b < 32; b++) {
+                    tmp[b] ^= message[(i * 4 + j) * 32 + b];
+                    message[(i * 4 + j) * 32 + b] = tmp[b];
+                }
+            }
+            secp256k1_scalar_set_b32(&s[npub], tmp, &overflow);
+            ret &= !(overflow || secp256k1_scalar_is_zero(&s[npub]));
+            npub++;
+        }
+    }
+    secp256k1_rfc6979_hmac_sha256_finalize(&rng);
+    secp256k1_scalar_clear(&acc);
+    memset(tmp, 0, 32);
+    return ret;
+}
+
+SECP256K1_INLINE static int secp256k1_range_proveparams(uint64_t *v, size_t *rings, size_t *rsizes, size_t *npub, size_t *secidx, uint64_t *min_value,
+ int *mantissa, uint64_t *scale,  int *exp, int *min_bits, uint64_t value) {
+    size_t i;
+    *rings = 1;
+    rsizes[0] = 1;
+    secidx[0] = 0;
+    *scale = 1;
+    *mantissa = 0;
+    *npub = 0;
+    if (*min_value == UINT64_MAX) {
+        /* If the minimum value is the maximal representable value, then we cannot code a range. */
+        *exp = -1;
+    }
+    if (*exp >= 0) {
+        int max_bits;
+        uint64_t v2;
+        if ((*min_value && value > INT64_MAX) || (value && *min_value >= INT64_MAX)) {
+            /* If either value or min_value is >= 2^63-1 then the other must by zero to avoid overflowing the proven range. */
+            return 0;
+        }
+        max_bits = *min_value ? secp256k1_clz64_var(*min_value) : 64;
+        if (*min_bits > max_bits) {
+            *min_bits = max_bits;
+        }
+        if (*min_bits > 61 || value > INT64_MAX) {
+            /** Ten is not a power of two, so dividing by ten and then representing in base-2 times ten
+             *   expands the representable range. The verifier requires the proven range is within 0..2**64.
+             *   For very large numbers (all over 2**63) we must change our exponent to compensate.
+             *  Rather than handling it precisely, this just disables use of the exponent for big values.
+             */
+            *exp = 0;
+        }
+        /* Mask off the least significant digits, as requested. */
+        *v = value - *min_value;
+        /* If the user has asked for more bits of proof then there is room for in the exponent, reduce the exponent. */
+        v2 = *min_bits ? (UINT64_MAX>>(64-*min_bits)) : 0;
+        for (i = 0; (int) i < *exp && (v2 <= UINT64_MAX / 10); i++) {
+            *v /= 10;
+            v2 *= 10;
+        }
+        *exp = i;
+        v2 = *v;
+        for (i = 0; (int) i < *exp; i++) {
+            v2 *= 10;
+            *scale *= 10;
+        }
+        /* If the masked number isn't precise, compute the public offset. */
+        *min_value = value - v2;
+        /* How many bits do we need to represent our value? */
+        *mantissa = *v ? 64 - secp256k1_clz64_var(*v) : 1;
+        if (*min_bits > *mantissa) {
+            /* If the user asked for more precision, give it to them. */
+            *mantissa = *min_bits;
+        }
+        /* Digits in radix-4, except for the last digit if our mantissa length is odd. */
+        *rings = (*mantissa + 1) >> 1;
+        for (i = 0; i < *rings; i++) {
+            rsizes[i] = ((i < *rings - 1) | (!(*mantissa&1))) ? 4 : 2;
+            *npub += rsizes[i];
+            secidx[i] = (*v >> (i*2)) & 3;
+        }
+        VERIFY_CHECK(*mantissa>0);
+        VERIFY_CHECK((*v & ~(UINT64_MAX>>(64-*mantissa))) == 0); /* Did this get all the bits? */
+    } else {
+        /* A proof for an exact value. */
+        *exp = 0;
+        *min_value = value;
+        *v = 0;
+        *npub = 2;
+    }
+    VERIFY_CHECK(*v * *scale + *min_value == value);
+    VERIFY_CHECK(*rings > 0);
+    VERIFY_CHECK(*rings <= 32);
+    VERIFY_CHECK(*npub <= 128);
+    return 1;
+}
+
+/* strawman interface, writes proof in proof, a buffer of plen, proves with respect to min_value the range for commit which has the provided blinding factor and value. */
+SECP256K1_INLINE static int secp256k1_rangeproof_sign_impl(const secp256k1_ecmult_context* ecmult_ctx,
+ const secp256k1_ecmult_gen_context* ecmult_gen_ctx,
+ unsigned char *proof, size_t *plen, uint64_t min_value,
+ const secp256k1_ge *commit, const unsigned char *blind, const unsigned char *nonce, int exp, int min_bits, uint64_t value,
+ const unsigned char *message, size_t msg_len, const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_ge* genp){
+    secp256k1_gej pubs[128];     /* Candidate digits for our proof, most inferred. */
+    secp256k1_scalar s[128];     /* Signatures in our proof, most forged. */
+    secp256k1_scalar sec[32];    /* Blinding factors for the correct digits. */
+    secp256k1_scalar k[32];      /* Nonces for our non-forged signatures. */
+    secp256k1_scalar stmp;
+    secp256k1_sha256 sha256_m;
+    unsigned char prep[4096];
+    unsigned char tmp[33];
+    unsigned char *signs;          /* Location of sign flags in the proof. */
+    uint64_t v;
+    uint64_t scale;                /* scale = 10^exp. */
+    int mantissa;                  /* Number of bits proven in the blinded value. */
+    size_t rings;                     /* How many digits will our proof cover. */
+    size_t rsizes[32];                /* How many possible values there are for each place. */
+    size_t secidx[32];                /* Which digit is the correct one. */
+    size_t len;                       /* Number of bytes used so far. */
+    size_t i;
+    int overflow;
+    size_t npub;
+    len = 0;
+    if (*plen < 65 || min_value > value || min_bits > 64 || min_bits < 0 || exp < -1 || exp > 18) {
+        return 0;
+    }
+    if (!secp256k1_range_proveparams(&v, &rings, rsizes, &npub, secidx, &min_value, &mantissa, &scale, &exp, &min_bits, value)) {
+        return 0;
+    }
+    proof[len] = (rsizes[0] > 1 ? (64 | exp) : 0) | (min_value ? 32 : 0);
+    len++;
+    if (rsizes[0] > 1) {
+        VERIFY_CHECK(mantissa > 0 && mantissa <= 64);
+        proof[len] = mantissa - 1;
+        len++;
+    }
+    if (min_value) {
+        for (i = 0; i < 8; i++) {
+            proof[len + i] = (min_value >> ((7-i) * 8)) & 255;
+        }
+        len += 8;
+    }
+    /* Do we have enough room in the proof for the message? Each ring gives us 128 bytes, but the
+     * final ring is used to encode the blinding factor and the value, so we can't use that. (Well,
+     * technically there are 64 bytes available if we avoided the other data, but this is difficult
+     * because it's not always in the same place. */
+    if (msg_len > 0 && msg_len > 128 * (rings - 1)) {
+        return 0;
+    }
+    /* Do we have enough room for the proof? */
+    if (*plen - len < 32 * (npub + rings - 1) + 32 + ((rings+6) >> 3)) {
+        return 0;
+    }
+    secp256k1_sha256_initialize(&sha256_m);
+    secp256k1_rangeproof_serialize_point(tmp, commit);
+    secp256k1_sha256_write(&sha256_m, tmp, 33);
+    secp256k1_rangeproof_serialize_point(tmp, genp);
+    secp256k1_sha256_write(&sha256_m, tmp, 33);
+    secp256k1_sha256_write(&sha256_m, proof, len);
+
+    memset(prep, 0, 4096);
+    if (message != NULL) {
+        memcpy(prep, message, msg_len);
+    }
+    /* Note, the data corresponding to the blinding factors must be zero. */
+    if (rsizes[rings - 1] > 1) {
+        size_t idx;
+        /* Value encoding sidechannel. */
+        idx = rsizes[rings - 1] - 1;
+        idx -= secidx[rings - 1] == idx;
+        idx = ((rings - 1) * 4 + idx) * 32;
+        for (i = 0; i < 8; i++) {
+            prep[8 + i + idx] = prep[16 + i + idx] = prep[24 + i + idx] = (v >> (56 - i * 8)) & 255;
+            prep[i + idx] = 0;
+        }
+        prep[idx] = 128;
+    }
+    if (!secp256k1_rangeproof_genrand(sec, s, prep, rsizes, rings, nonce, commit, proof, len, genp)) {
+        return 0;
+    }
+    memset(prep, 0, 4096);
+    for (i = 0; i < rings; i++) {
+        /* Sign will overwrite the non-forged signature, move that random value into the nonce. */
+        k[i] = s[i * 4 + secidx[i]];
+        secp256k1_scalar_clear(&s[i * 4 + secidx[i]]);
+    }
+    /** Genrand returns the last blinding factor as -sum(rest),
+     *   adding in the blinding factor for our commitment, results in the blinding factor for
+     *   the commitment to the last digit that the verifier can compute for itself by subtracting
+     *   all the digits in the proof from the commitment. This lets the prover skip sending the
+     *   blinded value for one digit.
+     */
+    secp256k1_scalar_set_b32(&stmp, blind, &overflow);
+    secp256k1_scalar_add(&sec[rings - 1], &sec[rings - 1], &stmp);
+    if (overflow || secp256k1_scalar_is_zero(&sec[rings - 1])) {
+        return 0;
+    }
+    signs = &proof[len];
+    /* We need one sign bit for each blinded value we send. */
+    for (i = 0; i < (rings + 6) >> 3; i++) {
+        signs[i] = 0;
+        len++;
+    }
+    npub = 0;
+    for (i = 0; i < rings; i++) {
+        /*OPT: Use the precomputed gen2 basis?*/
+        secp256k1_pedersen_ecmult(ecmult_gen_ctx, &pubs[npub], &sec[i], ((uint64_t)secidx[i] * scale) << (i*2), genp);
+        if (secp256k1_gej_is_infinity(&pubs[npub])) {
+            return 0;
+        }
+        if (i < rings - 1) {
+            unsigned char tmpc[33];
+            secp256k1_ge c;
+            unsigned char quadness;
+            /*OPT: split loop and batch invert.*/
+            /*OPT: do not compute full pubs[npub] in ge form; we only need x */
+            secp256k1_ge_set_gej_var(&c, &pubs[npub]);
+            secp256k1_rangeproof_serialize_point(tmpc, &c);
+            quadness = tmpc[0];
+            secp256k1_sha256_write(&sha256_m, tmpc, 33);
+            signs[i>>3] |= quadness << (i&7);
+            memcpy(&proof[len], tmpc + 1, 32);
+            len += 32;
+        }
+        npub += rsizes[i];
+    }
+    secp256k1_rangeproof_pub_expand(pubs, exp, rsizes, rings, genp);
+    if (extra_commit != NULL) {
+        secp256k1_sha256_write(&sha256_m, extra_commit, extra_commit_len);
+    }
+    secp256k1_sha256_finalize(&sha256_m, tmp);
+    if (!secp256k1_borromean_sign(ecmult_ctx, ecmult_gen_ctx, &proof[len], s, pubs, k, sec, rsizes, secidx, rings, tmp, 32)) {
+        return 0;
+    }
+    len += 32;
+    for (i = 0; i < npub; i++) {
+        secp256k1_scalar_get_b32(&proof[len],&s[i]);
+        len += 32;
+    }
+    VERIFY_CHECK(len <= *plen);
+    *plen = len;
+    memset(prep, 0, 4096);
+    return 1;
+}
+
+/* Computes blinding factor x given k, s, and the challenge e. */
+SECP256K1_INLINE static void secp256k1_rangeproof_recover_x(secp256k1_scalar *x, const secp256k1_scalar *k, const secp256k1_scalar *e,
+ const secp256k1_scalar *s) {
+    secp256k1_scalar stmp;
+    secp256k1_scalar_negate(x, s);
+    secp256k1_scalar_add(x, x, k);
+    secp256k1_scalar_inverse(&stmp, e);
+    secp256k1_scalar_mul(x, x, &stmp);
+}
+
+/* Computes ring's nonce given the blinding factor x, the challenge e, and the signature s. */
+SECP256K1_INLINE static void secp256k1_rangeproof_recover_k(secp256k1_scalar *k, const secp256k1_scalar *x, const secp256k1_scalar *e,
+ const secp256k1_scalar *s) {
+    secp256k1_scalar stmp;
+    secp256k1_scalar_mul(&stmp, x, e);
+    secp256k1_scalar_add(k, s, &stmp);
+}
+
+SECP256K1_INLINE static void secp256k1_rangeproof_ch32xor(unsigned char *x, const unsigned char *y) {
+    int i;
+    for (i = 0; i < 32; i++) {
+        x[i] ^= y[i];
+    }
+}
+
+SECP256K1_INLINE static int secp256k1_rangeproof_rewind_inner(secp256k1_scalar *blind, uint64_t *v,
+ unsigned char *m, size_t *mlen, secp256k1_scalar *ev, secp256k1_scalar *s,
+ size_t *rsizes, size_t rings, const unsigned char *nonce, const secp256k1_ge *commit, const unsigned char *proof, size_t len, const secp256k1_ge *genp) {
+    secp256k1_scalar s_orig[128];
+    secp256k1_scalar sec[32];
+    secp256k1_scalar stmp;
+    unsigned char prep[4096];
+    unsigned char tmp[32];
+    uint64_t value;
+    size_t offset;
+    size_t i;
+    size_t j;
+    int b;
+    size_t skip1;
+    size_t skip2;
+    size_t npub;
+    npub = ((rings - 1) << 2) + rsizes[rings-1];
+    VERIFY_CHECK(npub <= 128);
+    VERIFY_CHECK(npub >= 1);
+    memset(prep, 0, 4096);
+    /* Reconstruct the provers random values. */
+    secp256k1_rangeproof_genrand(sec, s_orig, prep, rsizes, rings, nonce, commit, proof, len, genp);
+    *v = UINT64_MAX;
+    secp256k1_scalar_clear(blind);
+    if (rings == 1 && rsizes[0] == 1) {
+        /* With only a single proof, we can only recover the blinding factor. */
+        secp256k1_rangeproof_recover_x(blind, &s_orig[0], &ev[0], &s[0]);
+        if (v) {
+            *v = 0;
+        }
+        if (mlen) {
+            *mlen = 0;
+        }
+        return 1;
+    }
+    npub = (rings - 1) << 2;
+    for (j = 0; j < 2; j++) {
+        size_t idx;
+        /* Look for a value encoding in the last ring. */
+        idx = npub + rsizes[rings - 1] - 1 - j;
+        secp256k1_scalar_get_b32(tmp, &s[idx]);
+        secp256k1_rangeproof_ch32xor(tmp, &prep[idx * 32]);
+        if ((tmp[0] & 128) && (memcmp(&tmp[16], &tmp[24], 8) == 0) && (memcmp(&tmp[8], &tmp[16], 8) == 0)) {
+            value = 0;
+            for (i = 0; i < 8; i++) {
+                value = (value << 8) + tmp[24 + i];
+            }
+            if (v) {
+                *v = value;
+            }
+            memcpy(&prep[idx * 32], tmp, 32);
+            break;
+        }
+    }
+    if (j > 1) {
+        /* Couldn't extract a value. */
+        if (mlen) {
+            *mlen = 0;
+        }
+        return 0;
+    }
+    skip1 = rsizes[rings - 1] - 1 - j;
+    skip2 = ((value >> ((rings - 1) << 1)) & 3);
+    if (skip1 == skip2) {
+        /*Value is in wrong position.*/
+        if (mlen) {
+            *mlen = 0;
+        }
+        return 0;
+    }
+    skip1 += (rings - 1) << 2;
+    skip2 += (rings - 1) << 2;
+    /* Like in the rsize[] == 1 case, Having figured out which s is the one which was not forged, we can recover the blinding factor. */
+    secp256k1_rangeproof_recover_x(&stmp, &s_orig[skip2], &ev[skip2], &s[skip2]);
+    secp256k1_scalar_negate(&sec[rings - 1], &sec[rings - 1]);
+    secp256k1_scalar_add(blind, &stmp, &sec[rings - 1]);
+    if (!m || !mlen || *mlen == 0) {
+        if (mlen) {
+            *mlen = 0;
+        }
+        /* FIXME: cleanup in early out/failure cases. */
+        return 1;
+    }
+    offset = 0;
+    npub = 0;
+    for (i = 0; i < rings; i++) {
+        size_t idx;
+        idx = (value >> (i << 1)) & 3;
+        for (j = 0; j < rsizes[i]; j++) {
+            if (npub == skip1 || npub == skip2) {
+                npub++;
+                continue;
+            }
+            if (idx == j) {
+                /** For the non-forged signatures the signature is calculated instead of random, instead we recover the prover's nonces.
+                 *  this could just as well recover the blinding factors and messages could be put there as is done for recovering the
+                 *  blinding factor in the last ring, but it takes an inversion to recover x so it's faster to put the message data in k.
+                 */
+                secp256k1_rangeproof_recover_k(&stmp, &sec[i], &ev[npub], &s[npub]);
+            } else {
+                stmp = s[npub];
+            }
+            secp256k1_scalar_get_b32(tmp, &stmp);
+            secp256k1_rangeproof_ch32xor(tmp, &prep[npub * 32]);
+            for (b = 0; b < 32 && offset < *mlen; b++) {
+                m[offset] = tmp[b];
+                offset++;
+            }
+            npub++;
+        }
+    }
+    *mlen = offset;
+    memset(prep, 0, 4096);
+    for (i = 0; i < 128; i++) {
+        secp256k1_scalar_clear(&s_orig[i]);
+    }
+    for (i = 0; i < 32; i++) {
+        secp256k1_scalar_clear(&sec[i]);
+    }
+    secp256k1_scalar_clear(&stmp);
+    return 1;
+}
+
+SECP256K1_INLINE static int secp256k1_rangeproof_getheader_impl(size_t *offset, int *exp, int *mantissa, uint64_t *scale,
+ uint64_t *min_value, uint64_t *max_value, const unsigned char *proof, size_t plen) {
+    int i;
+    int has_nz_range;
+    int has_min;
+    if (plen < 65 || ((proof[*offset] & 128) != 0)) {
+        return 0;
+    }
+    has_nz_range = proof[*offset] & 64;
+    has_min = proof[*offset] & 32;
+    *exp = -1;
+    *mantissa = 0;
+    if (has_nz_range) {
+        *exp = proof[*offset] & 31;
+        *offset += 1;
+        if (*exp > 18) {
+           return 0;
+        }
+        *mantissa = proof[*offset] + 1;
+        if (*mantissa > 64) {
+            return 0;
+         }
+        *max_value = UINT64_MAX>>(64-*mantissa);
+    } else {
+        *max_value = 0;
+    }
+    *offset += 1;
+    *scale = 1;
+    for (i = 0; i < *exp; i++) {
+        if (*max_value > UINT64_MAX / 10) {
+            return 0;
+        }
+        *max_value *= 10;
+        *scale *= 10;
+    }
+    *min_value = 0;
+    if (has_min) {
+        if(plen - *offset < 8) {
+            return 0;
+        }
+        /*FIXME: Compact minvalue encoding?*/
+        for (i = 0; i < 8; i++) {
+            *min_value = (*min_value << 8) | proof[*offset + i];
+        }
+        *offset += 8;
+    }
+    if (*max_value > UINT64_MAX - *min_value) {
+        return 0;
+    }
+    *max_value += *min_value;
+    return 1;
+}
+
+/* Verifies range proof (len plen) for commit, the min/max values proven are put in the min/max arguments; returns 0 on failure 1 on success.*/
+SECP256K1_INLINE static int secp256k1_rangeproof_verify_impl(const secp256k1_ecmult_context* ecmult_ctx,
+ const secp256k1_ecmult_gen_context* ecmult_gen_ctx,
+ unsigned char *blindout, uint64_t *value_out, unsigned char *message_out, size_t *outlen, const unsigned char *nonce,
+ uint64_t *min_value, uint64_t *max_value, const secp256k1_ge *commit, const unsigned char *proof, size_t plen, const unsigned char *extra_commit, size_t extra_commit_len, const secp256k1_ge* genp) {
+    secp256k1_gej accj;
+    secp256k1_gej pubs[128];
+    secp256k1_ge c;
+    secp256k1_scalar s[128];
+    secp256k1_scalar evalues[128]; /* Challenges, only used during proof rewind. */
+    secp256k1_sha256 sha256_m;
+    size_t rsizes[32];
+    int ret;
+    size_t i;
+    int exp;
+    int mantissa;
+    size_t offset;
+    size_t rings;
+    int overflow;
+    size_t npub;
+    int offset_post_header;
+    uint64_t scale;
+    unsigned char signs[31];
+    unsigned char m[33];
+    const unsigned char *e0;
+    offset = 0;
+    if (!secp256k1_rangeproof_getheader_impl(&offset, &exp, &mantissa, &scale, min_value, max_value, proof, plen)) {
+        return 0;
+    }
+    offset_post_header = offset;
+    rings = 1;
+    rsizes[0] = 1;
+    npub = 1;
+    if (mantissa != 0) {
+        rings = (mantissa >> 1);
+        for (i = 0; i < rings; i++) {
+            rsizes[i] = 4;
+        }
+        npub = (mantissa >> 1) << 2;
+        if (mantissa & 1) {
+            rsizes[rings] = 2;
+            npub += rsizes[rings];
+            rings++;
+        }
+    }
+    VERIFY_CHECK(rings <= 32);
+    if (plen - offset < 32 * (npub + rings - 1) + 32 + ((rings+6) >> 3)) {
+        return 0;
+    }
+    secp256k1_sha256_initialize(&sha256_m);
+    secp256k1_rangeproof_serialize_point(m, commit);
+    secp256k1_sha256_write(&sha256_m, m, 33);
+    secp256k1_rangeproof_serialize_point(m, genp);
+    secp256k1_sha256_write(&sha256_m, m, 33);
+    secp256k1_sha256_write(&sha256_m, proof, offset);
+    for(i = 0; i < rings - 1; i++) {
+        signs[i] = (proof[offset + ( i>> 3)] & (1 << (i & 7))) != 0;
+    }
+    offset += (rings + 6) >> 3;
+    if ((rings - 1) & 7) {
+        /* Number of coded blinded points is not a multiple of 8, force extra sign bits to 0 to reject mutation. */
+        if ((proof[offset - 1] >> ((rings - 1) & 7)) != 0) {
+            return 0;
+        }
+    }
+    npub = 0;
+    secp256k1_gej_set_infinity(&accj);
+    if (*min_value) {
+        secp256k1_pedersen_ecmult_small(&accj, *min_value, genp);
+    }
+    for(i = 0; i < rings - 1; i++) {
+        secp256k1_fe fe;
+        if (!secp256k1_fe_set_b32(&fe, &proof[offset]) ||
+            !secp256k1_ge_set_xquad(&c, &fe)) {
+            return 0;
+        }
+        if (signs[i]) {
+            secp256k1_ge_neg(&c, &c);
+        }
+        /* Not using secp256k1_rangeproof_serialize_point as we almost have it
+         * serialized form already. */
+        secp256k1_sha256_write(&sha256_m, &signs[i], 1);
+        secp256k1_sha256_write(&sha256_m, &proof[offset], 32);
+        secp256k1_gej_set_ge(&pubs[npub], &c);
+        secp256k1_gej_add_ge_var(&accj, &accj, &c, NULL);
+        offset += 32;
+        npub += rsizes[i];
+    }
+    secp256k1_gej_neg(&accj, &accj);
+    secp256k1_gej_add_ge_var(&pubs[npub], &accj, commit, NULL);
+    if (secp256k1_gej_is_infinity(&pubs[npub])) {
+        return 0;
+    }
+    secp256k1_rangeproof_pub_expand(pubs, exp, rsizes, rings, genp);
+    npub += rsizes[rings - 1];
+    e0 = &proof[offset];
+    offset += 32;
+    for (i = 0; i < npub; i++) {
+        secp256k1_scalar_set_b32(&s[i], &proof[offset], &overflow);
+        if (overflow) {
+            return 0;
+        }
+        offset += 32;
+    }
+    if (offset != plen) {
+        /*Extra data found, reject.*/
+        return 0;
+    }
+    if (extra_commit != NULL) {
+        secp256k1_sha256_write(&sha256_m, extra_commit, extra_commit_len);
+    }
+    secp256k1_sha256_finalize(&sha256_m, m);
+    ret = secp256k1_borromean_verify(ecmult_ctx, nonce ? evalues : NULL, e0, s, pubs, rsizes, rings, m, 32);
+    if (ret && nonce) {
+        /* Given the nonce, try rewinding the witness to recover its initial state. */
+        secp256k1_scalar blind;
+        uint64_t vv;
+        if (!ecmult_gen_ctx) {
+            return 0;
+        }
+        if (!secp256k1_rangeproof_rewind_inner(&blind, &vv, message_out, outlen, evalues, s, rsizes, rings, nonce, commit, proof, offset_post_header, genp)) {
+            return 0;
+        }
+        /* Unwind apparently successful, see if the commitment can be reconstructed. */
+        /* FIXME: should check vv is in the mantissa's range. */
+        vv = (vv * scale) + *min_value;
+        secp256k1_pedersen_ecmult(ecmult_gen_ctx, &accj, &blind, vv, genp);
+        if (secp256k1_gej_is_infinity(&accj)) {
+            return 0;
+        }
+        secp256k1_gej_neg(&accj, &accj);
+        secp256k1_gej_add_ge_var(&accj, &accj, commit, NULL);
+        if (!secp256k1_gej_is_infinity(&accj)) {
+            return 0;
+        }
+        if (blindout) {
+            secp256k1_scalar_get_b32(blindout, &blind);
+        }
+        if (value_out) {
+            *value_out = vv;
+        }
+    }
+    return ret;
+}
+
+#endif

src/modules/rangeproof/tests_impl.h

@@ -0,0 +1,709 @@
+/**********************************************************************
+ * Copyright (c) 2015 Gregory Maxwell                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_RANGEPROOF_TESTS
+#define SECP256K1_MODULE_RANGEPROOF_TESTS
+
+#include <string.h>
+
+#include "group.h"
+#include "scalar.h"
+#include "testrand.h"
+#include "util.h"
+
+#include "include/secp256k1_rangeproof.h"
+
+static void test_pedersen_api(const secp256k1_context *none, const secp256k1_context *sign, const secp256k1_context *vrfy, const int32_t *ecount) {
+    secp256k1_pedersen_commitment commit;
+    const secp256k1_pedersen_commitment *commit_ptr = &commit;
+    unsigned char blind[32];
+    unsigned char blind_out[32];
+    const unsigned char *blind_ptr = blind;
+    unsigned char *blind_out_ptr = blind_out;
+    uint64_t val = secp256k1_rand32();
+
+    secp256k1_rand256(blind);
+    CHECK(secp256k1_pedersen_commit(none, &commit, blind, val, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 1);
+    CHECK(secp256k1_pedersen_commit(vrfy, &commit, blind, val, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 2);
+    CHECK(secp256k1_pedersen_commit(sign, &commit, blind, val, secp256k1_generator_h) != 0);
+    CHECK(*ecount == 2);
+
+    CHECK(secp256k1_pedersen_commit(sign, NULL, blind, val, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 3);
+    CHECK(secp256k1_pedersen_commit(sign, &commit, NULL, val, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 4);
+    CHECK(secp256k1_pedersen_commit(sign, &commit, blind, val, NULL) == 0);
+    CHECK(*ecount == 5);
+
+    CHECK(secp256k1_pedersen_blind_sum(none, blind_out, &blind_ptr, 1, 1) != 0);
+    CHECK(*ecount == 5);
+    CHECK(secp256k1_pedersen_blind_sum(none, NULL, &blind_ptr, 1, 1) == 0);
+    CHECK(*ecount == 6);
+    CHECK(secp256k1_pedersen_blind_sum(none, blind_out, NULL, 1, 1) == 0);
+    CHECK(*ecount == 7);
+    CHECK(secp256k1_pedersen_blind_sum(none, blind_out, &blind_ptr, 0, 1) == 0);
+    CHECK(*ecount == 8);
+    CHECK(secp256k1_pedersen_blind_sum(none, blind_out, &blind_ptr, 0, 0) != 0);
+    CHECK(*ecount == 8);
+
+    CHECK(secp256k1_pedersen_commit(sign, &commit, blind, val, secp256k1_generator_h) != 0);
+    CHECK(secp256k1_pedersen_verify_tally(none, &commit_ptr, 1, &commit_ptr, 1) != 0);
+    CHECK(secp256k1_pedersen_verify_tally(none, NULL, 0, &commit_ptr, 1) == 0);
+    CHECK(secp256k1_pedersen_verify_tally(none, &commit_ptr, 1, NULL, 0) == 0);
+    CHECK(secp256k1_pedersen_verify_tally(none, NULL, 0, NULL, 0) != 0);
+    CHECK(*ecount == 8);
+    CHECK(secp256k1_pedersen_verify_tally(none, NULL, 1, &commit_ptr, 1) == 0);
+    CHECK(*ecount == 9);
+    CHECK(secp256k1_pedersen_verify_tally(none, &commit_ptr, 1, NULL, 1) == 0);
+    CHECK(*ecount == 10);
+
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, &val, &blind_ptr, &blind_out_ptr, 1, 0) != 0);
+    CHECK(*ecount == 10);
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, &val, &blind_ptr, &blind_out_ptr, 1, 1) == 0);
+    CHECK(*ecount == 11);
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, &val, &blind_ptr, &blind_out_ptr, 0, 0) == 0);
+    CHECK(*ecount == 12);
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, NULL, &blind_ptr, &blind_out_ptr, 1, 0) == 0);
+    CHECK(*ecount == 13);
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, &val, NULL, &blind_out_ptr, 1, 0) == 0);
+    CHECK(*ecount == 14);
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(none, &val, &blind_ptr, NULL, 1, 0) == 0);
+    CHECK(*ecount == 15);
+}
+
+static void test_rangeproof_api(const secp256k1_context *none, const secp256k1_context *sign, const secp256k1_context *vrfy, const secp256k1_context *both, const int32_t *ecount) {
+    unsigned char proof[5134];
+    unsigned char blind[32];
+    secp256k1_pedersen_commitment commit;
+    uint64_t vmin = secp256k1_rand32();
+    uint64_t val = vmin + secp256k1_rand32();
+    size_t len = sizeof(proof);
+    /* we'll switch to dylan thomas for this one */
+    const unsigned char message[68] = "My tears are like the quiet drift / Of petals from some magic rose;";
+    size_t mlen = sizeof(message);
+    const unsigned char ext_commit[72] = "And all my grief flows from the rift / Of unremembered skies and snows.";
+    size_t ext_commit_len = sizeof(ext_commit);
+
+    secp256k1_rand256(blind);
+    CHECK(secp256k1_pedersen_commit(ctx, &commit, blind, val, secp256k1_generator_h));
+
+    CHECK(secp256k1_rangeproof_sign(none, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 1);
+    CHECK(secp256k1_rangeproof_sign(sign, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 2);
+    CHECK(secp256k1_rangeproof_sign(vrfy, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 3);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+    CHECK(*ecount == 3);
+
+    CHECK(secp256k1_rangeproof_sign(both, NULL, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 4);
+    CHECK(secp256k1_rangeproof_sign(both, proof, NULL, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 5);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, NULL, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 6);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, NULL, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 7);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, NULL, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 8);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, vmin - 1, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 8);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, NULL, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 9);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, NULL, 0, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+    CHECK(*ecount == 9);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, NULL, 0, NULL, ext_commit_len, secp256k1_generator_h) == 0);
+    CHECK(*ecount == 10);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, NULL, 0, NULL, 0, secp256k1_generator_h) != 0);
+    CHECK(*ecount == 10);
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, NULL, 0, NULL, 0, NULL) == 0);
+    CHECK(*ecount == 11);
+
+    CHECK(secp256k1_rangeproof_sign(both, proof, &len, vmin, &commit, blind, commit.data, 0, 0, val, message, mlen, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+    {
+        int exp;
+        int mantissa;
+        uint64_t min_value;
+        uint64_t max_value;
+        CHECK(secp256k1_rangeproof_info(none, &exp, &mantissa, &min_value, &max_value, proof, len) != 0);
+        CHECK(exp == 0);
+        CHECK(((uint64_t) 1 << mantissa) > val - vmin);
+        CHECK(((uint64_t) 1 << (mantissa - 1)) <= val - vmin);
+        CHECK(min_value == vmin);
+        CHECK(max_value >= val);
+
+        CHECK(secp256k1_rangeproof_info(none, NULL, &mantissa, &min_value, &max_value, proof, len) == 0);
+        CHECK(*ecount == 12);
+        CHECK(secp256k1_rangeproof_info(none, &exp, NULL, &min_value, &max_value, proof, len) == 0);
+        CHECK(*ecount == 13);
+        CHECK(secp256k1_rangeproof_info(none, &exp, &mantissa, NULL, &max_value, proof, len) == 0);
+        CHECK(*ecount == 14);
+        CHECK(secp256k1_rangeproof_info(none, &exp, &mantissa, &min_value, NULL, proof, len) == 0);
+        CHECK(*ecount == 15);
+        CHECK(secp256k1_rangeproof_info(none, &exp, &mantissa, &min_value, &max_value, NULL, len) == 0);
+        CHECK(*ecount == 16);
+        CHECK(secp256k1_rangeproof_info(none, &exp, &mantissa, &min_value, &max_value, proof, 0) == 0);
+        CHECK(*ecount == 16);
+    }
+    {
+        uint64_t min_value;
+        uint64_t max_value;
+        CHECK(secp256k1_rangeproof_verify(none, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 17);
+        CHECK(secp256k1_rangeproof_verify(sign, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 18);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+        CHECK(*ecount == 18);
+
+        CHECK(secp256k1_rangeproof_verify(vrfy, NULL, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 19);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, NULL, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 20);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, NULL, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 21);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, NULL, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 22);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, proof, 0, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 22);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, proof, len, NULL, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 23);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, proof, len, NULL, 0, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 23);
+        CHECK(secp256k1_rangeproof_verify(vrfy, &min_value, &max_value, &commit, proof, len, NULL, 0, NULL) == 0);
+        CHECK(*ecount == 24);
+    }
+    {
+        unsigned char blind_out[32];
+        unsigned char message_out[68];
+        uint64_t value_out;
+        uint64_t min_value;
+        uint64_t max_value;
+        size_t message_len = sizeof(message_out);
+
+        CHECK(secp256k1_rangeproof_rewind(none, blind_out, &value_out, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 25);
+        CHECK(secp256k1_rangeproof_rewind(sign, blind_out, &value_out, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 26);
+        CHECK(secp256k1_rangeproof_rewind(vrfy, blind_out, &value_out, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 27);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+        CHECK(*ecount == 27);
+
+        CHECK(min_value == vmin);
+        CHECK(max_value >= val);
+        CHECK(value_out == val);
+        CHECK(message_len == sizeof(message_out));
+        CHECK(memcmp(message, message_out, sizeof(message_out)) == 0);
+
+        CHECK(secp256k1_rangeproof_rewind(both, NULL, &value_out, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+        CHECK(*ecount == 27);  /* blindout may be NULL */
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, NULL, message_out, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+        CHECK(*ecount == 27);  /* valueout may be NULL */
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, &message_len, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 28);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) != 0);
+        CHECK(*ecount == 28);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, NULL, &min_value, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 29);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, NULL, &max_value, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 30);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, NULL, &commit, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 31);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, NULL, proof, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 32);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, NULL, len, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 33);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, proof, 0, ext_commit, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 33);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, proof, len, NULL, ext_commit_len, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 34);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, proof, len, NULL, 0, secp256k1_generator_h) == 0);
+        CHECK(*ecount == 34);
+        CHECK(secp256k1_rangeproof_rewind(both, blind_out, &value_out, NULL, 0, commit.data, &min_value, &max_value, &commit, proof, len, NULL, 0, NULL) == 0);
+        CHECK(*ecount == 35);
+    }
+}
+
+static void test_api(void) {
+    secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
+    secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    secp256k1_context *both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+    int32_t ecount;
+    int i;
+
+    secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(both, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(both, counting_illegal_callback_fn, &ecount);
+
+    for (i = 0; i < count; i++) {
+        ecount = 0;
+        test_pedersen_api(none, sign, vrfy, &ecount);
+        ecount = 0;
+        test_rangeproof_api(none, sign, vrfy, both, &ecount);
+    }
+
+    secp256k1_context_destroy(none);
+    secp256k1_context_destroy(sign);
+    secp256k1_context_destroy(vrfy);
+    secp256k1_context_destroy(both);
+}
+
+static void test_pedersen(void) {
+    secp256k1_pedersen_commitment commits[19];
+    const secp256k1_pedersen_commitment *cptr[19];
+    unsigned char blinds[32*19];
+    const unsigned char *bptr[19];
+    secp256k1_scalar s;
+    uint64_t values[19];
+    int64_t totalv;
+    int i;
+    int inputs;
+    int outputs;
+    int total;
+    inputs = (secp256k1_rand32() & 7) + 1;
+    outputs = (secp256k1_rand32() & 7) + 2;
+    total = inputs + outputs;
+    for (i = 0; i < 19; i++) {
+        cptr[i] = &commits[i];
+        bptr[i] = &blinds[i * 32];
+    }
+    totalv = 0;
+    for (i = 0; i < inputs; i++) {
+        values[i] = secp256k1_rands64(0, INT64_MAX - totalv);
+        totalv += values[i];
+    }
+    for (i = 0; i < outputs - 1; i++) {
+        values[i + inputs] = secp256k1_rands64(0, totalv);
+        totalv -= values[i + inputs];
+    }
+    values[total - 1] = totalv;
+
+    for (i = 0; i < total - 1; i++) {
+        random_scalar_order(&s);
+        secp256k1_scalar_get_b32(&blinds[i * 32], &s);
+    }
+    CHECK(secp256k1_pedersen_blind_sum(ctx, &blinds[(total - 1) * 32], bptr, total - 1, inputs));
+    for (i = 0; i < total; i++) {
+        CHECK(secp256k1_pedersen_commit(ctx, &commits[i], &blinds[i * 32], values[i], secp256k1_generator_h));
+    }
+    CHECK(secp256k1_pedersen_verify_tally(ctx, cptr, inputs, &cptr[inputs], outputs));
+    CHECK(secp256k1_pedersen_verify_tally(ctx, &cptr[inputs], outputs, cptr, inputs));
+    if (inputs > 0 && values[0] > 0) {
+        CHECK(!secp256k1_pedersen_verify_tally(ctx, cptr, inputs - 1, &cptr[inputs], outputs));
+    }
+    random_scalar_order(&s);
+    for (i = 0; i < 4; i++) {
+        secp256k1_scalar_get_b32(&blinds[i * 32], &s);
+    }
+    values[0] = INT64_MAX;
+    values[1] = 0;
+    values[2] = 1;
+    for (i = 0; i < 3; i++) {
+        CHECK(secp256k1_pedersen_commit(ctx, &commits[i], &blinds[i * 32], values[i], secp256k1_generator_h));
+    }
+    CHECK(secp256k1_pedersen_verify_tally(ctx, &cptr[0], 1, &cptr[0], 1));
+    CHECK(secp256k1_pedersen_verify_tally(ctx, &cptr[1], 1, &cptr[1], 1));
+}
+
+static void test_borromean(void) {
+    unsigned char e0[32];
+    secp256k1_scalar s[64];
+    secp256k1_gej pubs[64];
+    secp256k1_scalar k[8];
+    secp256k1_scalar sec[8];
+    secp256k1_ge ge;
+    secp256k1_scalar one;
+    unsigned char m[32];
+    size_t rsizes[8];
+    size_t secidx[8];
+    size_t nrings;
+    size_t i;
+    size_t j;
+    int c;
+    secp256k1_rand256_test(m);
+    nrings = 1 + (secp256k1_rand32()&7);
+    c = 0;
+    secp256k1_scalar_set_int(&one, 1);
+    if (secp256k1_rand32()&1) {
+        secp256k1_scalar_negate(&one, &one);
+    }
+    for (i = 0; i < nrings; i++) {
+        rsizes[i] = 1 + (secp256k1_rand32()&7);
+        secidx[i] = secp256k1_rand32() % rsizes[i];
+        random_scalar_order(&sec[i]);
+        random_scalar_order(&k[i]);
+        if(secp256k1_rand32()&7) {
+            sec[i] = one;
+        }
+        if(secp256k1_rand32()&7) {
+            k[i] = one;
+        }
+        for (j = 0; j < rsizes[i]; j++) {
+            random_scalar_order(&s[c + j]);
+            if(secp256k1_rand32()&7) {
+                s[i] = one;
+            }
+            if (j == secidx[i]) {
+                secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &pubs[c + j], &sec[i]);
+            } else {
+                random_group_element_test(&ge);
+                random_group_element_jacobian_test(&pubs[c + j],&ge);
+            }
+        }
+        c += rsizes[i];
+    }
+    CHECK(secp256k1_borromean_sign(&ctx->ecmult_ctx, &ctx->ecmult_gen_ctx, e0, s, pubs, k, sec, rsizes, secidx, nrings, m, 32));
+    CHECK(secp256k1_borromean_verify(&ctx->ecmult_ctx, NULL, e0, s, pubs, rsizes, nrings, m, 32));
+    i = secp256k1_rand32() % c;
+    secp256k1_scalar_negate(&s[i],&s[i]);
+    CHECK(!secp256k1_borromean_verify(&ctx->ecmult_ctx, NULL, e0, s, pubs, rsizes, nrings, m, 32));
+    secp256k1_scalar_negate(&s[i],&s[i]);
+    secp256k1_scalar_set_int(&one, 1);
+    for(j = 0; j < 4; j++) {
+        i = secp256k1_rand32() % c;
+        if (secp256k1_rand32() & 1) {
+            secp256k1_gej_double_var(&pubs[i],&pubs[i], NULL);
+        } else {
+            secp256k1_scalar_add(&s[i],&s[i],&one);
+        }
+        CHECK(!secp256k1_borromean_verify(&ctx->ecmult_ctx, NULL, e0, s, pubs, rsizes, nrings, m, 32));
+    }
+}
+
+static void test_rangeproof(void) {
+    const uint64_t testvs[11] = {0, 1, 5, 11, 65535, 65537, INT32_MAX, UINT32_MAX, INT64_MAX - 1, INT64_MAX, UINT64_MAX};
+    secp256k1_pedersen_commitment commit;
+    secp256k1_pedersen_commitment commit2;
+    unsigned char proof[5134 + 1]; /* One additional byte to test if trailing bytes are rejected */
+    unsigned char blind[32];
+    unsigned char blindout[32];
+    unsigned char message[4096];
+    size_t mlen;
+    uint64_t v;
+    uint64_t vout;
+    uint64_t vmin;
+    uint64_t minv;
+    uint64_t maxv;
+    size_t len;
+    size_t i;
+    size_t j;
+    size_t k;
+    /* Short message is a Simone de Beauvoir quote */
+    const unsigned char message_short[120] = "When I see my own likeness in the depths of someone else's consciousness,  I always experience a moment of panic.";
+    /* Long message is 0xA5 with a bunch of this quote in the middle */
+    unsigned char message_long[3968];
+    memset(message_long, 0xa5, sizeof(message_long));
+    for (i = 1200; i < 3600; i += 120) {
+        memcpy(&message_long[i], message_short, sizeof(message_short));
+    }
+
+    secp256k1_rand256(blind);
+    for (i = 0; i < 11; i++) {
+        v = testvs[i];
+        CHECK(secp256k1_pedersen_commit(ctx, &commit, blind, v, secp256k1_generator_h));
+        for (vmin = 0; vmin < (i<9 && i > 0 ? 2 : 1); vmin++) {
+            const unsigned char *input_message = NULL;
+            size_t input_message_len = 0;
+            /* vmin is always either 0 or 1; if it is 1, then we have no room for a message.
+             * If it's 0, we use "minimum encoding" and only have room for a small message when
+             * `testvs[i]` is >= 4; for a large message when it's >= 2^32. */
+            if (vmin == 0 && i > 2) {
+                input_message = message_short;
+                input_message_len = sizeof(message_short);
+            }
+            if (vmin == 0 && i > 7) {
+                input_message = message_long;
+                input_message_len = sizeof(message_long);
+            }
+            len = 5134;
+            CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, vmin, &commit, blind, commit.data, 0, 0, v, input_message, input_message_len, NULL, 0, secp256k1_generator_h));
+            CHECK(len <= 5134);
+            mlen = 4096;
+            CHECK(secp256k1_rangeproof_rewind(ctx, blindout, &vout, message, &mlen, commit.data, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+            if (input_message != NULL) {
+                CHECK(memcmp(message, input_message, input_message_len) == 0);
+            }
+            for (j = input_message_len; j < mlen; j++) {
+                CHECK(message[j] == 0);
+            }
+            CHECK(mlen <= 4096);
+            CHECK(memcmp(blindout, blind, 32) == 0);
+            CHECK(vout == v);
+            CHECK(minv <= v);
+            CHECK(maxv >= v);
+            len = 5134;
+            CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, v, &commit, blind, commit.data, -1, 64, v, NULL, 0, NULL, 0, secp256k1_generator_h));
+            CHECK(len <= 73);
+            CHECK(secp256k1_rangeproof_rewind(ctx, blindout, &vout, NULL, NULL, commit.data, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+            CHECK(memcmp(blindout, blind, 32) == 0);
+            CHECK(vout == v);
+            CHECK(minv == v);
+            CHECK(maxv == v);
+
+            /* Check with a committed message */
+            len = 5134;
+            CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, v, &commit, blind, commit.data, -1, 64, v, NULL, 0, message_short, sizeof(message_short), secp256k1_generator_h));
+            CHECK(len <= 73);
+            CHECK(!secp256k1_rangeproof_rewind(ctx, blindout, &vout, NULL, NULL, commit.data, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+            CHECK(!secp256k1_rangeproof_rewind(ctx, blindout, &vout, NULL, NULL, commit.data, &minv, &maxv, &commit, proof, len, message_long, sizeof(message_long), secp256k1_generator_h));
+            CHECK(secp256k1_rangeproof_rewind(ctx, blindout, &vout, NULL, NULL, commit.data, &minv, &maxv, &commit, proof, len, message_short, sizeof(message_short), secp256k1_generator_h));
+            CHECK(memcmp(blindout, blind, 32) == 0);
+            CHECK(vout == v);
+            CHECK(minv == v);
+            CHECK(maxv == v);
+        }
+    }
+    secp256k1_rand256(blind);
+    v = INT64_MAX - 1;
+    CHECK(secp256k1_pedersen_commit(ctx, &commit, blind, v, secp256k1_generator_h));
+    for (i = 0; i < 19; i++) {
+        len = 5134;
+        CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, 0, &commit, blind, commit.data, i, 0, v, NULL, 0, NULL, 0, secp256k1_generator_h));
+        CHECK(secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+        CHECK(len <= 5134);
+        CHECK(minv <= v);
+        CHECK(maxv >= v);
+        /* Make sure it fails when validating with a committed message */
+        CHECK(!secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit, proof, len, message_short, sizeof(message_short), secp256k1_generator_h));
+    }
+    secp256k1_rand256(blind);
+    {
+        /*Malleability test.*/
+        v = secp256k1_rands64(0, 255);
+        CHECK(secp256k1_pedersen_commit(ctx, &commit, blind, v, secp256k1_generator_h));
+        len = 5134;
+        CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, 0, &commit, blind, commit.data, 0, 3, v, NULL, 0, NULL, 0, secp256k1_generator_h));
+        CHECK(len <= 5134);
+        /* Test if trailing bytes are rejected. */
+        proof[len] = v;
+        CHECK(!secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit, proof, len + 1, NULL, 0, secp256k1_generator_h));
+        for (i = 0; i < len*8; i++) {
+            proof[i >> 3] ^= 1 << (i & 7);
+            CHECK(!secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+            proof[i >> 3] ^= 1 << (i & 7);
+        }
+        CHECK(secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+        CHECK(minv <= v);
+        CHECK(maxv >= v);
+    }
+    memcpy(&commit2, &commit, sizeof(commit));
+    for (i = 0; i < (size_t) 2*count; i++) {
+        int exp;
+        int min_bits;
+        v = secp256k1_rands64(0, UINT64_MAX >> (secp256k1_rand32()&63));
+        vmin = 0;
+        if ((v < INT64_MAX) && (secp256k1_rand32()&1)) {
+            vmin = secp256k1_rands64(0, v);
+        }
+        secp256k1_rand256(blind);
+        CHECK(secp256k1_pedersen_commit(ctx, &commit, blind, v, secp256k1_generator_h));
+        len = 5134;
+        exp = (int)secp256k1_rands64(0,18)-(int)secp256k1_rands64(0,18);
+        if (exp < 0) {
+            exp = -exp;
+        }
+        min_bits = (int)secp256k1_rands64(0,64)-(int)secp256k1_rands64(0,64);
+        if (min_bits < 0) {
+            min_bits = -min_bits;
+        }
+        CHECK(secp256k1_rangeproof_sign(ctx, proof, &len, vmin, &commit, blind, commit.data, exp, min_bits, v, NULL, 0, NULL, 0, secp256k1_generator_h));
+        CHECK(len <= 5134);
+        mlen = 4096;
+        CHECK(secp256k1_rangeproof_rewind(ctx, blindout, &vout, message, &mlen, commit.data, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+        for (j = 0; j < mlen; j++) {
+            CHECK(message[j] == 0);
+        }
+        CHECK(mlen <= 4096);
+        CHECK(memcmp(blindout, blind, 32) == 0);
+
+        CHECK(minv <= v);
+        CHECK(maxv >= v);
+        CHECK(secp256k1_rangeproof_rewind(ctx, blindout, &vout, NULL, NULL, commit.data, &minv, &maxv, &commit, proof, len, NULL, 0, secp256k1_generator_h));
+        memcpy(&commit2, &commit, sizeof(commit));
+    }
+    for (j = 0; j < 5; j++) {
+        for (i = 0; i < 96; i++) {
+            secp256k1_rand256(&proof[i * 32]);
+        }
+        for (k = 0; k < 128; k++) {
+            len = k;
+            CHECK(!secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit2, proof, len, NULL, 0, secp256k1_generator_h));
+        }
+        len = secp256k1_rands64(0, 3072);
+        CHECK(!secp256k1_rangeproof_verify(ctx, &minv, &maxv, &commit2, proof, len, NULL, 0, secp256k1_generator_h));
+    }
+}
+
+#define MAX_N_GENS	30
+void test_multiple_generators(void) {
+    const size_t n_inputs = (secp256k1_rand32() % (MAX_N_GENS / 2)) + 1;
+    const size_t n_outputs = (secp256k1_rand32() % (MAX_N_GENS / 2)) + 1;
+    const size_t n_generators = n_inputs + n_outputs;
+    unsigned char *generator_blind[MAX_N_GENS];
+    unsigned char *pedersen_blind[MAX_N_GENS];
+    secp256k1_generator generator[MAX_N_GENS];
+    secp256k1_pedersen_commitment commit[MAX_N_GENS];
+    const secp256k1_pedersen_commitment *commit_ptr[MAX_N_GENS];
+    size_t i;
+    int64_t total_value;
+    uint64_t value[MAX_N_GENS];
+
+    secp256k1_scalar s;
+
+    unsigned char generator_seed[32];
+    random_scalar_order(&s);
+    secp256k1_scalar_get_b32(generator_seed, &s);
+    /* Create all the needed generators */
+    for (i = 0; i < n_generators; i++) {
+        generator_blind[i] = (unsigned char*) malloc(32);
+        pedersen_blind[i] = (unsigned char*) malloc(32);
+
+        random_scalar_order(&s);
+        secp256k1_scalar_get_b32(generator_blind[i], &s);
+        random_scalar_order(&s);
+        secp256k1_scalar_get_b32(pedersen_blind[i], &s);
+
+        CHECK(secp256k1_generator_generate_blinded(ctx, &generator[i], generator_seed, generator_blind[i]));
+
+        commit_ptr[i] = &commit[i];
+    }
+
+    /* Compute all the values -- can be positive or negative */
+    total_value = 0;
+    for (i = 0; i < n_outputs; i++) {
+        value[n_inputs + i] = secp256k1_rands64(0, INT64_MAX - total_value);
+        total_value += value[n_inputs + i];
+    }
+    for (i = 0; i < n_inputs - 1; i++) {
+        value[i] = secp256k1_rands64(0, total_value);
+        total_value -= value[i];
+    }
+    value[i] = total_value;
+
+    /* Correct for blinding factors and do the commitments */
+    CHECK(secp256k1_pedersen_blind_generator_blind_sum(ctx, value, (const unsigned char * const *) generator_blind, pedersen_blind, n_generators, n_inputs));
+    for (i = 0; i < n_generators; i++) {
+        CHECK(secp256k1_pedersen_commit(ctx, &commit[i], pedersen_blind[i], value[i], &generator[i]));
+    }
+
+    /* Verify */
+    CHECK(secp256k1_pedersen_verify_tally(ctx, &commit_ptr[0], n_inputs, &commit_ptr[n_inputs], n_outputs));
+
+    /* Cleanup */
+    for (i = 0; i < n_generators; i++) {
+        free(generator_blind[i]);
+        free(pedersen_blind[i]);
+    }
+}
+
+void test_rangeproof_fixed_vectors(void) {
+    const unsigned char vector_1[] = {
+        0x62, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x56, 0x02, 0x2a, 0x5c, 0x42, 0x0e, 0x1d,
+        0x51, 0xe1, 0xb7, 0xf3, 0x69, 0x04, 0xb5, 0xbb, 0x9b, 0x41, 0x66, 0x14, 0xf3, 0x64, 0x42, 0x26,
+        0xe3, 0xa7, 0x6a, 0x06, 0xbb, 0xa8, 0x5a, 0x49, 0x6f, 0x19, 0x76, 0xfb, 0xe5, 0x75, 0x77, 0x88,
+        0xab, 0xa9, 0x66, 0x44, 0x80, 0xea, 0x29, 0x95, 0x7f, 0xdf, 0x72, 0x4a, 0xaf, 0x02, 0xbe, 0xdd,
+        0x5d, 0x15, 0xd8, 0xae, 0xff, 0x74, 0xc9, 0x8c, 0x1a, 0x67, 0x0e, 0xb2, 0x57, 0x22, 0x99, 0xc3,
+        0x21, 0x46, 0x6f, 0x15, 0x58, 0x0e, 0xdb, 0xe6, 0x6e, 0xc4, 0x0d, 0xfe, 0x6f, 0x04, 0x6b, 0x0d,
+        0x18, 0x3d, 0x78, 0x40, 0x98, 0x56, 0x4e, 0xe4, 0x4a, 0x74, 0x90, 0xa7, 0xac, 0x9c, 0x16, 0xe0,
+        0x3e, 0x81, 0xaf, 0x0f, 0xe3, 0x4f, 0x34, 0x99, 0x52, 0xf7, 0xa7, 0xf6, 0xd3, 0x83, 0xa0, 0x17,
+        0x4b, 0x2d, 0xa7, 0xd4, 0xfd, 0xf7, 0x84, 0x45, 0xc4, 0x11, 0x71, 0x3d, 0x4a, 0x22, 0x34, 0x09,
+        0x9c, 0xa7, 0xe5, 0xc8, 0xba, 0x04, 0xbf, 0xfd, 0x25, 0x11, 0x7d, 0xa4, 0x43, 0x45, 0xc7, 0x62,
+        0x9e, 0x7b, 0x80, 0xf6, 0x09, 0xbb, 0x1b, 0x2e, 0xf3, 0xcd, 0x23, 0xe0, 0xed, 0x81, 0x43, 0x42,
+        0xbe, 0xc4, 0x9f, 0x58, 0x8a, 0x0d, 0x66, 0x79, 0x09, 0x70, 0x11, 0x68, 0x3d, 0x87, 0x38, 0x1c,
+        0x3c, 0x85, 0x52, 0x5b, 0x62, 0xf7, 0x3e, 0x7e, 0x87, 0xa2, 0x99, 0x24, 0xd0, 0x7d, 0x18, 0x63,
+        0x56, 0x48, 0xa4, 0x3a, 0xfe, 0x65, 0xfa, 0xa4, 0xd0, 0x67, 0xaa, 0x98, 0x65, 0x4d, 0xe4, 0x22,
+        0x75, 0x45, 0x52, 0xe8, 0x41, 0xc7, 0xed, 0x38, 0xeb, 0xf5, 0x02, 0x90, 0xc9, 0x45, 0xa3, 0xb0,
+        0x4d, 0x03, 0xd7, 0xab, 0x43, 0xe4, 0x21, 0xfc, 0x83, 0xd6, 0x12, 0x1d, 0x76, 0xb1, 0x3c, 0x67,
+        0x63, 0x1f, 0x52, 0x9d, 0xc3, 0x23, 0x5c, 0x4e, 0xa6, 0x8d, 0x01, 0x4a, 0xba, 0x9a, 0xf4, 0x16,
+        0x5b, 0x67, 0xc8, 0xe1, 0xd2, 0x42, 0x6d, 0xdf, 0xcd, 0x08, 0x6a, 0x73, 0x41, 0x6a, 0xc2, 0x84,
+        0xc6, 0x31, 0xbe, 0x57, 0xcb, 0x0e, 0xde, 0xbf, 0x71, 0xd5, 0x8a, 0xf7, 0x24, 0xb2, 0xa7, 0x89,
+        0x96, 0x62, 0x4f, 0xd9, 0xf7, 0xc3, 0xde, 0x4c, 0xab, 0x13, 0x72, 0xb4, 0xb3, 0x35, 0x04, 0x82,
+        0xa8, 0x75, 0x1d, 0xde, 0x46, 0xa8, 0x0d, 0xb8, 0x23, 0x44, 0x00, 0x44, 0xfa, 0x53, 0x6c, 0x2d,
+        0xce, 0xd3, 0xa6, 0x80, 0xa1, 0x20, 0xca, 0xd1, 0x63, 0xbb, 0xbe, 0x39, 0x5f, 0x9d, 0x27, 0x69,
+        0xb3, 0x33, 0x1f, 0xdb, 0xda, 0x67, 0x05, 0x37, 0xbe, 0x65, 0xe9, 0x7e, 0xa9, 0xc3, 0xff, 0x37,
+        0x8a, 0xb4, 0x2d, 0xfe, 0xf2, 0x16, 0x85, 0xc7, 0x0f, 0xd9, 0xbe, 0x14, 0xd1, 0x80, 0x14, 0x9f,
+        0x58, 0x56, 0x98, 0x41, 0xf6, 0x26, 0xf7, 0xa2, 0x71, 0x66, 0xb4, 0x7a, 0x9c, 0x12, 0x73, 0xd3,
+        0xdf, 0x77, 0x2b, 0x49, 0xe5, 0xca, 0x50, 0x57, 0x44, 0x6e, 0x3f, 0x58, 0x56, 0xbc, 0x21, 0x70,
+        0x4f, 0xc6, 0xaa, 0x12, 0xff, 0x7c, 0xa7, 0x3d, 0xed, 0x46, 0xc1, 0x40, 0xe6, 0x58, 0x09, 0x2a,
+        0xda, 0xb3, 0x76, 0xab, 0x44, 0xb5, 0x4e, 0xb3, 0x12, 0xe0, 0x26, 0x8a, 0x52, 0xac, 0x49, 0x1d,
+        0xe7, 0x06, 0x53, 0x3a, 0x01, 0x35, 0x21, 0x2e, 0x86, 0x48, 0xc5, 0x75, 0xc1, 0xa2, 0x7d, 0x22,
+        0x53, 0xf6, 0x3f, 0x41, 0xc5, 0xb3, 0x08, 0x7d, 0xa3, 0x67, 0xc0, 0xbb, 0xb6, 0x8d, 0xf0, 0xd3,
+        0x01, 0x72, 0xd3, 0x63, 0x82, 0x01, 0x1a, 0xe7, 0x1d, 0x22, 0xfa, 0x95, 0x33, 0xf6, 0xf2, 0xde,
+        0xa2, 0x53, 0x86, 0x55, 0x5a, 0xb4, 0x2e, 0x75, 0x75, 0xc6, 0xd5, 0x93, 0x9c, 0x57, 0xa9, 0x1f,
+        0xb9, 0x3e, 0xe8, 0x1c, 0xbf, 0xac, 0x1c, 0x54, 0x6f, 0xf5, 0xab, 0x41, 0xee, 0xb3, 0x0e, 0xd0,
+        0x76, 0xc4, 0x1a, 0x45, 0xcd, 0xf1, 0xd6, 0xcc, 0xb0, 0x83, 0x70, 0x73, 0xbc, 0x88, 0x74, 0xa0,
+        0x5b, 0xe7, 0x98, 0x10, 0x36, 0xbf, 0xec, 0x23, 0x1c, 0xc2, 0xb5, 0xba, 0x4b, 0x9d, 0x7f, 0x8c,
+        0x8a, 0xe2, 0xda, 0x18, 0xdd, 0xab, 0x27, 0x8a, 0x15, 0xeb, 0xb0, 0xd4, 0x3a, 0x8b, 0x77, 0x00,
+        0xc7, 0xbb, 0xcc, 0xfa, 0xba, 0xa4, 0x6a, 0x17, 0x5c, 0xf8, 0x51, 0x5d, 0x8d, 0x16, 0xcd, 0xa7,
+        0x0e, 0x71, 0x97, 0x98, 0x78, 0x5a, 0x41, 0xb3, 0xf0, 0x1f, 0x87, 0x2d, 0x65, 0xcd, 0x29, 0x49,
+        0xd2, 0x87, 0x2c, 0x91, 0xa9, 0x5f, 0xcc, 0xa9, 0xd8, 0xbb, 0x53, 0x18, 0xe7, 0xd6, 0xec, 0x65,
+        0xa6, 0x45, 0xf6, 0xce, 0xcf, 0x48, 0xf6, 0x1e, 0x3d, 0xd2, 0xcf, 0xcb, 0x3a, 0xcd, 0xbb, 0x92,
+        0x29, 0x24, 0x16, 0x7f, 0x8a, 0xa8, 0x5c, 0x0c, 0x45, 0x71, 0x33
+    };
+    const unsigned char commit_1[] = {
+        0x08,
+        0xf5, 0x1e, 0x0d, 0xc5, 0x86, 0x78, 0x51, 0xa9, 0x00, 0x00, 0xef, 0x4d, 0xe2, 0x94, 0x60, 0x89,
+        0x83, 0x04, 0xb4, 0x0e, 0x90, 0x10, 0x05, 0x1c, 0x7f, 0xd7, 0x33, 0x92, 0x1f, 0xe7, 0x74, 0x59
+    };
+    uint64_t min_value_1;
+    uint64_t max_value_1;
+    secp256k1_pedersen_commitment pc;
+
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &pc, commit_1));
+
+    CHECK(secp256k1_rangeproof_verify(
+        ctx,
+        &min_value_1, &max_value_1,
+        &pc,
+        vector_1, sizeof(vector_1),
+        NULL, 0,
+        secp256k1_generator_h
+    ));
+}
+
+void test_pedersen_commitment_fixed_vector(void) {
+    const unsigned char two_g[33] = {
+        0x09,
+        0xc6, 0x04, 0x7f, 0x94, 0x41, 0xed, 0x7d, 0x6d, 0x30, 0x45, 0x40, 0x6e, 0x95, 0xc0, 0x7c, 0xd8,
+        0x5c, 0x77, 0x8e, 0x4b, 0x8c, 0xef, 0x3c, 0xa7, 0xab, 0xac, 0x09, 0xb9, 0x5c, 0x70, 0x9e, 0xe5
+    };
+    unsigned char result[33];
+    secp256k1_pedersen_commitment parse;
+
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &parse, two_g));
+    CHECK(secp256k1_pedersen_commitment_serialize(ctx, result, &parse));
+    CHECK(memcmp(two_g, result, 33) == 0);
+
+    result[0] = 0x08;
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &parse, result));
+    result[0] = 0x0c;
+    CHECK(!secp256k1_pedersen_commitment_parse(ctx, &parse, result));
+}
+
+void run_rangeproof_tests(void) {
+    int i;
+    test_api();
+    test_rangeproof_fixed_vectors();
+    test_pedersen_commitment_fixed_vector();
+    for (i = 0; i < 10*count; i++) {
+        test_pedersen();
+    }
+    for (i = 0; i < 10*count; i++) {
+        test_borromean();
+    }
+    test_rangeproof();
+    test_multiple_generators();
+}
+
+#endif

src/modules/schnorrsig/Makefile.am.include

@@ -0,0 +1,8 @@
+include_HEADERS += include/secp256k1_schnorrsig.h
+noinst_HEADERS += src/modules/schnorrsig/main_impl.h
+noinst_HEADERS += src/modules/schnorrsig/tests_impl.h
+if USE_BENCHMARK
+noinst_PROGRAMS += bench_schnorrsig
+bench_schnorrsig_SOURCES = src/bench_schnorrsig.c
+bench_schnorrsig_LDADD = libsecp256k1.la $(SECP_LIBS) $(COMMON_LIB)
+endif

src/modules/schnorrsig/main_impl.h

@@ -0,0 +1,338 @@
+/**********************************************************************
+ * Copyright (c) 2018 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_MODULE_SCHNORRSIG_MAIN_
+#define _SECP256K1_MODULE_SCHNORRSIG_MAIN_
+
+#include "include/secp256k1.h"
+#include "include/secp256k1_schnorrsig.h"
+#include "hash.h"
+
+int secp256k1_schnorrsig_serialize(const secp256k1_context* ctx, unsigned char *out64, const secp256k1_schnorrsig* sig) {
+    (void) ctx;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(out64 != NULL);
+    ARG_CHECK(sig != NULL);
+    memcpy(out64, sig->data, 64);
+    return 1;
+}
+
+int secp256k1_schnorrsig_parse(const secp256k1_context* ctx, secp256k1_schnorrsig* sig, const unsigned char *in64) {
+    (void) ctx;
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(in64 != NULL);
+    memcpy(sig->data, in64, 64);
+    return 1;
+}
+
+int secp256k1_schnorrsig_sign(const secp256k1_context* ctx, secp256k1_schnorrsig *sig, int *nonce_is_negated, const unsigned char *msg32, const unsigned char *seckey, secp256k1_nonce_function noncefp, void *ndata) {
+    secp256k1_scalar x;
+    secp256k1_scalar e;
+    secp256k1_scalar k;
+    secp256k1_gej pkj;
+    secp256k1_gej rj;
+    secp256k1_ge pk;
+    secp256k1_ge r;
+    secp256k1_sha256 sha;
+    int overflow;
+    unsigned char buf[33];
+    size_t buflen = sizeof(buf);
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(msg32 != NULL);
+    ARG_CHECK(seckey != NULL);
+
+    if (noncefp == NULL) {
+        noncefp = secp256k1_nonce_function_bipschnorr;
+    }
+    secp256k1_scalar_set_b32(&x, seckey, &overflow);
+    /* Fail if the secret key is invalid. */
+    if (overflow || secp256k1_scalar_is_zero(&x)) {
+        memset(sig, 0, sizeof(*sig));
+        return 0;
+    }
+
+    secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &pkj, &x);
+    secp256k1_ge_set_gej(&pk, &pkj);
+
+    if (!noncefp(buf, msg32, seckey, NULL, (void*)ndata, 0)) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&k, buf, NULL);
+    if (secp256k1_scalar_is_zero(&k)) {
+        return 0;
+    }
+
+    secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &rj, &k);
+    secp256k1_ge_set_gej(&r, &rj);
+
+    if (nonce_is_negated != NULL) {
+        *nonce_is_negated = 0;
+    }
+    if (!secp256k1_fe_is_quad_var(&r.y)) {
+        secp256k1_scalar_negate(&k, &k);
+        if (nonce_is_negated != NULL) {
+            *nonce_is_negated = 1;
+        }
+    }
+    secp256k1_fe_normalize(&r.x);
+    secp256k1_fe_get_b32(&sig->data[0], &r.x);
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, &sig->data[0], 32);
+    secp256k1_eckey_pubkey_serialize(&pk, buf, &buflen, 1);
+    secp256k1_sha256_write(&sha, buf, buflen);
+    secp256k1_sha256_write(&sha, msg32, 32);
+    secp256k1_sha256_finalize(&sha, buf);
+
+    secp256k1_scalar_set_b32(&e, buf, NULL);
+    secp256k1_scalar_mul(&e, &e, &x);
+    secp256k1_scalar_add(&e, &e, &k);
+
+    secp256k1_scalar_get_b32(&sig->data[32], &e);
+    secp256k1_scalar_clear(&k);
+    secp256k1_scalar_clear(&x);
+
+    return 1;
+}
+
+/* Helper function for verification and batch verification.
+ * Computes R = sG - eP. */
+static int secp256k1_schnorrsig_real_verify(const secp256k1_context* ctx, secp256k1_gej *rj, const secp256k1_scalar *s, const secp256k1_scalar *e, const secp256k1_pubkey *pk) {
+    secp256k1_scalar nege;
+    secp256k1_ge pkp;
+    secp256k1_gej pkj;
+
+    secp256k1_scalar_negate(&nege, e);
+
+    if (!secp256k1_pubkey_load(ctx, &pkp, pk)) {
+        return 0;
+    }
+    secp256k1_gej_set_ge(&pkj, &pkp);
+
+    /* rj =  s*G + (-e)*pkj */
+    secp256k1_ecmult(&ctx->ecmult_ctx, rj, &pkj, &nege, s);
+    return 1;
+}
+
+int secp256k1_schnorrsig_verify(const secp256k1_context* ctx, const secp256k1_schnorrsig *sig, const unsigned char *msg32, const secp256k1_pubkey *pk) {
+    secp256k1_scalar s;
+    secp256k1_scalar e;
+    secp256k1_gej rj;
+    secp256k1_fe rx;
+    secp256k1_sha256 sha;
+    unsigned char buf[33];
+    size_t buflen = sizeof(buf);
+    int overflow;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(msg32 != NULL);
+    ARG_CHECK(pk != NULL);
+
+    if (!secp256k1_fe_set_b32(&rx, &sig->data[0])) {
+        return 0;
+    }
+
+    secp256k1_scalar_set_b32(&s, &sig->data[32], &overflow);
+    if (overflow) {
+        return 0;
+    }
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, &sig->data[0], 32);
+    secp256k1_ec_pubkey_serialize(ctx, buf, &buflen, pk, SECP256K1_EC_COMPRESSED);
+    secp256k1_sha256_write(&sha, buf, buflen);
+    secp256k1_sha256_write(&sha, msg32, 32);
+    secp256k1_sha256_finalize(&sha, buf);
+    secp256k1_scalar_set_b32(&e, buf, NULL);
+
+    if (!secp256k1_schnorrsig_real_verify(ctx, &rj, &s, &e, pk)
+        || !secp256k1_gej_has_quad_y_var(&rj) /* fails if rj is infinity */
+        || !secp256k1_gej_eq_x_var(&rx, &rj)) {
+        return 0;
+    }
+
+    return 1;
+}
+
+/* Data that is used by the batch verification ecmult callback */
+typedef struct {
+    const secp256k1_context *ctx;
+    /* Seed for the random number generator */
+    unsigned char chacha_seed[32];
+    /* Caches randomizers generated by the PRNG which returns two randomizers per call. Caching
+     * avoids having to call the PRNG twice as often. The very first randomizer will be set to 1 and
+     * the PRNG is called at every odd indexed schnorrsig to fill the cache. */
+    secp256k1_scalar randomizer_cache[2];
+    /* Signature, message, public key tuples to verify */
+    const secp256k1_schnorrsig *const *sig;
+    const unsigned char *const *msg32;
+    const secp256k1_pubkey *const *pk;
+    size_t n_sigs;
+} secp256k1_schnorrsig_verify_ecmult_context;
+
+/* Callback function which is called by ecmult_multi in order to convert the ecmult_context
+ * consisting of signature, message and public key tuples into scalars and points. */
+static int secp256k1_schnorrsig_verify_batch_ecmult_callback(secp256k1_scalar *sc, secp256k1_ge *pt, size_t idx, void *data) {
+    secp256k1_schnorrsig_verify_ecmult_context *ecmult_context = (secp256k1_schnorrsig_verify_ecmult_context *) data;
+
+    if (idx % 4 == 2) {
+        /* Every idx corresponds to a (scalar,point)-tuple. So this callback is called with 4
+         * consecutive tuples before we need to call the RNG for new randomizers:
+         * (-randomizer_cache[0], R1)
+         * (-randomizer_cache[0]*e1, P1)
+         * (-randomizer_cache[1], R2)
+         * (-randomizer_cache[1]*e2, P2) */
+        secp256k1_scalar_chacha20(&ecmult_context->randomizer_cache[0], &ecmult_context->randomizer_cache[1], ecmult_context->chacha_seed, idx / 4);
+    }
+
+    /* R */
+    if (idx % 2 == 0) {
+        secp256k1_fe rx;
+        *sc = ecmult_context->randomizer_cache[(idx / 2) % 2];
+        if (!secp256k1_fe_set_b32(&rx, &ecmult_context->sig[idx / 2]->data[0])) {
+            return 0;
+        }
+        if (!secp256k1_ge_set_xquad(pt, &rx)) {
+            return 0;
+        }
+    /* eP */
+    } else {
+        unsigned char buf[33];
+        size_t buflen = sizeof(buf);
+        secp256k1_sha256 sha;
+        secp256k1_sha256_initialize(&sha);
+        secp256k1_sha256_write(&sha, &ecmult_context->sig[idx / 2]->data[0], 32);
+        secp256k1_ec_pubkey_serialize(ecmult_context->ctx, buf, &buflen, ecmult_context->pk[idx / 2], SECP256K1_EC_COMPRESSED);
+        secp256k1_sha256_write(&sha, buf, buflen);
+        secp256k1_sha256_write(&sha, ecmult_context->msg32[idx / 2], 32);
+        secp256k1_sha256_finalize(&sha, buf);
+
+        secp256k1_scalar_set_b32(sc, buf, NULL);
+        secp256k1_scalar_mul(sc, sc, &ecmult_context->randomizer_cache[(idx / 2) % 2]);
+
+        if (!secp256k1_pubkey_load(ecmult_context->ctx, pt, ecmult_context->pk[idx / 2])) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+/** Helper function for batch verification. Hashes signature verification data into the
+ *  randomization seed and initializes ecmult_context.
+ *
+ *  Returns 1 if the randomizer was successfully initialized.
+ *
+ *  Args:    ctx: a secp256k1 context object
+ *  Out: ecmult_context: context for batch_ecmult_callback
+ *  In/Out   sha: an initialized sha256 object which hashes the schnorrsig input in order to get a
+ *                seed for the randomizer PRNG
+ *  In:      sig: array of signatures, or NULL if there are no signatures
+ *         msg32: array of messages, or NULL if there are no signatures
+ *            pk: array of public keys, or NULL if there are no signatures
+ *        n_sigs: number of signatures in above arrays (must be 0 if they are NULL)
+ */
+int secp256k1_schnorrsig_verify_batch_init_randomizer(const secp256k1_context *ctx, secp256k1_schnorrsig_verify_ecmult_context *ecmult_context, secp256k1_sha256 *sha, const secp256k1_schnorrsig *const *sig, const unsigned char *const *msg32, const secp256k1_pubkey *const *pk, size_t n_sigs) {
+    size_t i;
+
+    if (n_sigs > 0) {
+        ARG_CHECK(sig != NULL);
+        ARG_CHECK(msg32 != NULL);
+        ARG_CHECK(pk != NULL);
+    }
+
+    for (i = 0; i < n_sigs; i++) {
+        unsigned char buf[33];
+        size_t buflen = sizeof(buf);
+        secp256k1_sha256_write(sha, sig[i]->data, 64);
+        secp256k1_sha256_write(sha, msg32[i], 32);
+        secp256k1_ec_pubkey_serialize(ctx, buf, &buflen, pk[i], SECP256K1_EC_COMPRESSED);
+        secp256k1_sha256_write(sha, buf, 32);
+    }
+    ecmult_context->ctx = ctx;
+    ecmult_context->sig = sig;
+    ecmult_context->msg32 = msg32;
+    ecmult_context->pk = pk;
+    ecmult_context->n_sigs = n_sigs;
+
+    return 1;
+}
+
+/** Helper function for batch verification. Sums the s part of all signatures multiplied by their
+ *  randomizer.
+ *
+ *  Returns 1 if s is successfully summed.
+ *
+ *  In/Out: s: the s part of the input sigs is added to this s argument
+ *  In:  chacha_seed: PRNG seed for computing randomizers
+ *        sig: array of signatures, or NULL if there are no signatures
+ *     n_sigs: number of signatures in above array (must be 0 if they are NULL)
+ */
+int secp256k1_schnorrsig_verify_batch_sum_s(secp256k1_scalar *s, unsigned char *chacha_seed, const secp256k1_schnorrsig *const *sig, size_t n_sigs) {
+    secp256k1_scalar randomizer_cache[2];
+    size_t i;
+
+    secp256k1_scalar_set_int(&randomizer_cache[0], 1);
+    for (i = 0; i < n_sigs; i++) {
+        int overflow;
+        secp256k1_scalar term;
+        if (i % 2 == 1) {
+            secp256k1_scalar_chacha20(&randomizer_cache[0], &randomizer_cache[1], chacha_seed, i / 2);
+        }
+
+        secp256k1_scalar_set_b32(&term, &sig[i]->data[32], &overflow);
+        if (overflow) {
+            return 0;
+        }
+        secp256k1_scalar_mul(&term, &term, &randomizer_cache[i % 2]);
+        secp256k1_scalar_add(s, s, &term);
+    }
+    return 1;
+}
+
+/* schnorrsig batch verification.
+ * Seeds a random number generator with the inputs and derives a random number ai for every
+ * signature i. Fails if y-coordinate of any R is not a quadratic residue or if
+ * 0 != -(s1 + a2*s2 + ... + au*su)G + R1 + a2*R2 + ... + au*Ru + e1*P1 + (a2*e2)P2 + ... + (au*eu)Pu. */
+int secp256k1_schnorrsig_verify_batch(const secp256k1_context *ctx, secp256k1_scratch *scratch, const secp256k1_schnorrsig *const *sig, const unsigned char *const *msg32, const secp256k1_pubkey *const *pk, size_t n_sigs) {
+    secp256k1_schnorrsig_verify_ecmult_context ecmult_context;
+    secp256k1_sha256 sha;
+    secp256k1_scalar s;
+    secp256k1_gej rj;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(scratch != NULL);
+    /* Check that n_sigs is less than half of the maximum size_t value. This is necessary because
+     * the number of points given to ecmult_multi is 2*n_sigs. */
+    ARG_CHECK(n_sigs <= SIZE_MAX / 2);
+    /* Check that n_sigs is less than 2^31 to ensure the same behavior of this function on 32-bit
+     * and 64-bit platforms. */
+    ARG_CHECK(n_sigs < (size_t)(1 << 31));
+
+    secp256k1_sha256_initialize(&sha);
+    if (!secp256k1_schnorrsig_verify_batch_init_randomizer(ctx, &ecmult_context, &sha, sig, msg32, pk, n_sigs)) {
+        return 0;
+    }
+    secp256k1_sha256_finalize(&sha, ecmult_context.chacha_seed);
+    secp256k1_scalar_set_int(&ecmult_context.randomizer_cache[0], 1);
+
+    secp256k1_scalar_clear(&s);
+    if (!secp256k1_schnorrsig_verify_batch_sum_s(&s, ecmult_context.chacha_seed, sig, n_sigs)) {
+        return 0;
+    }
+    secp256k1_scalar_negate(&s, &s);
+
+    return secp256k1_ecmult_multi_var(&ctx->ecmult_ctx, scratch, &rj, &s, secp256k1_schnorrsig_verify_batch_ecmult_callback, (void *) &ecmult_context, 2 * n_sigs)
+            && secp256k1_gej_is_infinity(&rj);
+}
+
+#endif

src/modules/schnorrsig/tests_impl.h

@@ -0,0 +1,726 @@
+/**********************************************************************
+ * Copyright (c) 2018 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_MODULE_SCHNORRSIG_TESTS_
+#define _SECP256K1_MODULE_SCHNORRSIG_TESTS_
+
+#include "secp256k1_schnorrsig.h"
+
+void test_schnorrsig_serialize(void) {
+    secp256k1_schnorrsig sig;
+    unsigned char in[64];
+    unsigned char out[64];
+
+    memset(in, 0x12, 64);
+    CHECK(secp256k1_schnorrsig_parse(ctx, &sig, in));
+    CHECK(secp256k1_schnorrsig_serialize(ctx, out, &sig));
+    CHECK(memcmp(in, out, 64) == 0);
+}
+
+void test_schnorrsig_api(secp256k1_scratch_space *scratch) {
+    unsigned char sk1[32];
+    unsigned char sk2[32];
+    unsigned char sk3[32];
+    unsigned char msg[32];
+    unsigned char sig64[64];
+    secp256k1_pubkey pk[3];
+    secp256k1_schnorrsig sig;
+    const secp256k1_schnorrsig *sigptr = &sig;
+    const unsigned char *msgptr = msg;
+    const secp256k1_pubkey *pkptr = &pk[0];
+    int nonce_is_negated;
+
+    /** setup **/
+    secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
+    secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    secp256k1_context *both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+    int ecount;
+
+    secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(both, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(both, counting_illegal_callback_fn, &ecount);
+
+    secp256k1_rand256(sk1);
+    secp256k1_rand256(sk2);
+    secp256k1_rand256(sk3);
+    secp256k1_rand256(msg);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk[0], sk1) == 1);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk[1], sk2) == 1);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk[2], sk3) == 1);
+
+    /** main test body **/
+    ecount = 0;
+    CHECK(secp256k1_schnorrsig_sign(none, &sig, &nonce_is_negated, msg, sk1, NULL, NULL) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_schnorrsig_sign(vrfy, &sig, &nonce_is_negated, msg, sk1, NULL, NULL) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_sign(sign, &sig, &nonce_is_negated, msg, sk1, NULL, NULL) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_sign(sign, NULL, &nonce_is_negated, msg, sk1, NULL, NULL) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_schnorrsig_sign(sign, &sig, NULL, msg, sk1, NULL, NULL) == 1);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_schnorrsig_sign(sign, &sig, &nonce_is_negated, NULL, sk1, NULL, NULL) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_schnorrsig_sign(sign, &sig, &nonce_is_negated, msg, NULL, NULL, NULL) == 0);
+    CHECK(ecount == 5);
+
+    ecount = 0;
+    CHECK(secp256k1_schnorrsig_serialize(none, sig64, &sig) == 1);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_schnorrsig_serialize(none, NULL, &sig) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_schnorrsig_serialize(none, sig64, NULL) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_parse(none, &sig, sig64) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_parse(none, NULL, sig64) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_schnorrsig_parse(none, &sig, NULL) == 0);
+    CHECK(ecount == 4);
+
+    ecount = 0;
+    CHECK(secp256k1_schnorrsig_verify(none, &sig, msg, &pk[0]) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_schnorrsig_verify(sign, &sig, msg, &pk[0]) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_verify(vrfy, &sig, msg, &pk[0]) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_verify(vrfy, NULL, msg, &pk[0]) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_schnorrsig_verify(vrfy, &sig, NULL, &pk[0]) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_schnorrsig_verify(vrfy, &sig, msg, NULL) == 0);
+    CHECK(ecount == 5);
+
+    ecount = 0;
+    CHECK(secp256k1_schnorrsig_verify_batch(none, scratch, &sigptr, &msgptr, &pkptr, 1) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_schnorrsig_verify_batch(sign, scratch, &sigptr, &msgptr, &pkptr, 1) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, &sigptr, &msgptr, &pkptr, 1) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, NULL, NULL, NULL, 0) == 1);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, NULL, &msgptr, &pkptr, 1) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, &sigptr, NULL, &pkptr, 1) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, &sigptr, &msgptr, NULL, 1) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, &sigptr, &msgptr, &pkptr, (size_t)1 << (sizeof(size_t)*8-1)) == 0);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_schnorrsig_verify_batch(vrfy, scratch, &sigptr, &msgptr, &pkptr, 1 << 31) == 0);
+    CHECK(ecount == 7);
+
+    secp256k1_context_destroy(none);
+    secp256k1_context_destroy(sign);
+    secp256k1_context_destroy(vrfy);
+    secp256k1_context_destroy(both);
+}
+
+/* Helper function for schnorrsig_bip_vectors
+ * Signs the message and checks that it's the same as expected_sig. */
+void test_schnorrsig_bip_vectors_check_signing(const unsigned char *sk, const unsigned char *pk_serialized, const unsigned char *msg, const unsigned char *expected_sig, const int expected_nonce_is_negated) {
+    secp256k1_schnorrsig sig;
+    unsigned char serialized_sig[64];
+    secp256k1_pubkey pk;
+    int nonce_is_negated;
+
+    CHECK(secp256k1_schnorrsig_sign(ctx, &sig, &nonce_is_negated, msg, sk, NULL, NULL));
+    CHECK(nonce_is_negated == expected_nonce_is_negated);
+    CHECK(secp256k1_schnorrsig_serialize(ctx, serialized_sig, &sig));
+    CHECK(memcmp(serialized_sig, expected_sig, 64) == 0);
+
+    CHECK(secp256k1_ec_pubkey_parse(ctx, &pk, pk_serialized, 33));
+    CHECK(secp256k1_schnorrsig_verify(ctx, &sig, msg, &pk));
+}
+
+/* Helper function for schnorrsig_bip_vectors
+ * Checks that both verify and verify_batch return the same value as expected. */
+void test_schnorrsig_bip_vectors_check_verify(secp256k1_scratch_space *scratch, const unsigned char *pk_serialized, const unsigned char *msg32, const unsigned char *sig_serialized, int expected) {
+    const unsigned char *msg_arr[1];
+    const secp256k1_schnorrsig *sig_arr[1];
+    const secp256k1_pubkey *pk_arr[1];
+    secp256k1_pubkey pk;
+    secp256k1_schnorrsig sig;
+
+    CHECK(secp256k1_ec_pubkey_parse(ctx, &pk, pk_serialized, 33));
+    CHECK(secp256k1_schnorrsig_parse(ctx, &sig, sig_serialized));
+
+    sig_arr[0] = &sig;
+    msg_arr[0] = msg32;
+    pk_arr[0] = &pk;
+
+    CHECK(expected == secp256k1_schnorrsig_verify(ctx, &sig, msg32, &pk));
+    CHECK(expected == secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 1));
+}
+
+/* Test vectors according to BIP-schnorr
+ * (https://github.com/sipa/bips/blob/7f6a73e53c8bbcf2d008ea0546f76433e22094a8/bip-schnorr/test-vectors.csv).
+ */
+void test_schnorrsig_bip_vectors(secp256k1_scratch_space *scratch) {
+    {
+        /* Test vector 1 */
+        const unsigned char sk1[32] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01
+        };
+        const unsigned char pk1[33] = {
+            0x02, 0x79, 0xBE, 0x66, 0x7E, 0xF9, 0xDC, 0xBB,
+            0xAC, 0x55, 0xA0, 0x62, 0x95, 0xCE, 0x87, 0x0B,
+            0x07, 0x02, 0x9B, 0xFC, 0xDB, 0x2D, 0xCE, 0x28,
+            0xD9, 0x59, 0xF2, 0x81, 0x5B, 0x16, 0xF8, 0x17,
+            0x98
+        };
+        const unsigned char msg1[32] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+        };
+        const unsigned char sig1[64] = {
+            0x78, 0x7A, 0x84, 0x8E, 0x71, 0x04, 0x3D, 0x28,
+            0x0C, 0x50, 0x47, 0x0E, 0x8E, 0x15, 0x32, 0xB2,
+            0xDD, 0x5D, 0x20, 0xEE, 0x91, 0x2A, 0x45, 0xDB,
+            0xDD, 0x2B, 0xD1, 0xDF, 0xBF, 0x18, 0x7E, 0xF6,
+            0x70, 0x31, 0xA9, 0x88, 0x31, 0x85, 0x9D, 0xC3,
+            0x4D, 0xFF, 0xEE, 0xDD, 0xA8, 0x68, 0x31, 0x84,
+            0x2C, 0xCD, 0x00, 0x79, 0xE1, 0xF9, 0x2A, 0xF1,
+            0x77, 0xF7, 0xF2, 0x2C, 0xC1, 0xDC, 0xED, 0x05
+        };
+        test_schnorrsig_bip_vectors_check_signing(sk1, pk1, msg1, sig1, 1);
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk1, msg1, sig1, 1);
+    }
+    {
+        /* Test vector 2 */
+        const unsigned char sk2[32] = {
+            0xB7, 0xE1, 0x51, 0x62, 0x8A, 0xED, 0x2A, 0x6A,
+            0xBF, 0x71, 0x58, 0x80, 0x9C, 0xF4, 0xF3, 0xC7,
+            0x62, 0xE7, 0x16, 0x0F, 0x38, 0xB4, 0xDA, 0x56,
+            0xA7, 0x84, 0xD9, 0x04, 0x51, 0x90, 0xCF, 0xEF
+        };
+        const unsigned char pk2[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg2[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig2[64] = {
+            0x2A, 0x29, 0x8D, 0xAC, 0xAE, 0x57, 0x39, 0x5A,
+            0x15, 0xD0, 0x79, 0x5D, 0xDB, 0xFD, 0x1D, 0xCB,
+            0x56, 0x4D, 0xA8, 0x2B, 0x0F, 0x26, 0x9B, 0xC7,
+            0x0A, 0x74, 0xF8, 0x22, 0x04, 0x29, 0xBA, 0x1D,
+            0x1E, 0x51, 0xA2, 0x2C, 0xCE, 0xC3, 0x55, 0x99,
+            0xB8, 0xF2, 0x66, 0x91, 0x22, 0x81, 0xF8, 0x36,
+            0x5F, 0xFC, 0x2D, 0x03, 0x5A, 0x23, 0x04, 0x34,
+            0xA1, 0xA6, 0x4D, 0xC5, 0x9F, 0x70, 0x13, 0xFD
+        };
+        test_schnorrsig_bip_vectors_check_signing(sk2, pk2, msg2, sig2, 0);
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk2, msg2, sig2, 1);
+    }
+    {
+        /* Test vector 3 */
+        const unsigned char sk3[32] = {
+            0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34,
+            0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
+            0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74,
+            0x02, 0x0B, 0xBE, 0xA6, 0x3B, 0x14, 0xE5, 0xC7
+        };
+        const unsigned char pk3[33] = {
+            0x03, 0xFA, 0xC2, 0x11, 0x4C, 0x2F, 0xBB, 0x09,
+            0x15, 0x27, 0xEB, 0x7C, 0x64, 0xEC, 0xB1, 0x1F,
+            0x80, 0x21, 0xCB, 0x45, 0xE8, 0xE7, 0x80, 0x9D,
+            0x3C, 0x09, 0x38, 0xE4, 0xB8, 0xC0, 0xE5, 0xF8,
+            0x4B
+        };
+        const unsigned char msg3[32] = {
+            0x5E, 0x2D, 0x58, 0xD8, 0xB3, 0xBC, 0xDF, 0x1A,
+            0xBA, 0xDE, 0xC7, 0x82, 0x90, 0x54, 0xF9, 0x0D,
+            0xDA, 0x98, 0x05, 0xAA, 0xB5, 0x6C, 0x77, 0x33,
+            0x30, 0x24, 0xB9, 0xD0, 0xA5, 0x08, 0xB7, 0x5C
+        };
+        const unsigned char sig3[64] = {
+            0x00, 0xDA, 0x9B, 0x08, 0x17, 0x2A, 0x9B, 0x6F,
+            0x04, 0x66, 0xA2, 0xDE, 0xFD, 0x81, 0x7F, 0x2D,
+            0x7A, 0xB4, 0x37, 0xE0, 0xD2, 0x53, 0xCB, 0x53,
+            0x95, 0xA9, 0x63, 0x86, 0x6B, 0x35, 0x74, 0xBE,
+            0x00, 0x88, 0x03, 0x71, 0xD0, 0x17, 0x66, 0x93,
+            0x5B, 0x92, 0xD2, 0xAB, 0x4C, 0xD5, 0xC8, 0xA2,
+            0xA5, 0x83, 0x7E, 0xC5, 0x7F, 0xED, 0x76, 0x60,
+            0x77, 0x3A, 0x05, 0xF0, 0xDE, 0x14, 0x23, 0x80
+        };
+        test_schnorrsig_bip_vectors_check_signing(sk3, pk3, msg3, sig3, 0);
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk3, msg3, sig3, 1);
+    }
+    {
+        /* Test vector 4 */
+        const unsigned char pk4[33] = {
+            0x03, 0xDE, 0xFD, 0xEA, 0x4C, 0xDB, 0x67, 0x77,
+            0x50, 0xA4, 0x20, 0xFE, 0xE8, 0x07, 0xEA, 0xCF,
+            0x21, 0xEB, 0x98, 0x98, 0xAE, 0x79, 0xB9, 0x76,
+            0x87, 0x66, 0xE4, 0xFA, 0xA0, 0x4A, 0x2D, 0x4A,
+            0x34
+        };
+        const unsigned char msg4[32] = {
+            0x4D, 0xF3, 0xC3, 0xF6, 0x8F, 0xCC, 0x83, 0xB2,
+            0x7E, 0x9D, 0x42, 0xC9, 0x04, 0x31, 0xA7, 0x24,
+            0x99, 0xF1, 0x78, 0x75, 0xC8, 0x1A, 0x59, 0x9B,
+            0x56, 0x6C, 0x98, 0x89, 0xB9, 0x69, 0x67, 0x03
+        };
+        const unsigned char sig4[64] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x3B, 0x78, 0xCE, 0x56, 0x3F,
+            0x89, 0xA0, 0xED, 0x94, 0x14, 0xF5, 0xAA, 0x28,
+            0xAD, 0x0D, 0x96, 0xD6, 0x79, 0x5F, 0x9C, 0x63,
+            0x02, 0xA8, 0xDC, 0x32, 0xE6, 0x4E, 0x86, 0xA3,
+            0x33, 0xF2, 0x0E, 0xF5, 0x6E, 0xAC, 0x9B, 0xA3,
+            0x0B, 0x72, 0x46, 0xD6, 0xD2, 0x5E, 0x22, 0xAD,
+            0xB8, 0xC6, 0xBE, 0x1A, 0xEB, 0x08, 0xD4, 0x9D
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk4, msg4, sig4, 1);
+    }
+    {
+        /* Test vector 5 */
+        const unsigned char pk5[33] = {
+            0x03, 0x1B, 0x84, 0xC5, 0x56, 0x7B, 0x12, 0x64,
+            0x40, 0x99, 0x5D, 0x3E, 0xD5, 0xAA, 0xBA, 0x05,
+            0x65, 0xD7, 0x1E, 0x18, 0x34, 0x60, 0x48, 0x19,
+            0xFF, 0x9C, 0x17, 0xF5, 0xE9, 0xD5, 0xDD, 0x07,
+            0x8F
+        };
+        const unsigned char msg5[32] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+        };
+        const unsigned char sig5[64] = {
+            0x52, 0x81, 0x85, 0x79, 0xAC, 0xA5, 0x97, 0x67,
+            0xE3, 0x29, 0x1D, 0x91, 0xB7, 0x6B, 0x63, 0x7B,
+            0xEF, 0x06, 0x20, 0x83, 0x28, 0x49, 0x92, 0xF2,
+            0xD9, 0x5F, 0x56, 0x4C, 0xA6, 0xCB, 0x4E, 0x35,
+            0x30, 0xB1, 0xDA, 0x84, 0x9C, 0x8E, 0x83, 0x04,
+            0xAD, 0xC0, 0xCF, 0xE8, 0x70, 0x66, 0x03, 0x34,
+            0xB3, 0xCF, 0xC1, 0x8E, 0x82, 0x5E, 0xF1, 0xDB,
+            0x34, 0xCF, 0xAE, 0x3D, 0xFC, 0x5D, 0x81, 0x87
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk5, msg5, sig5, 1);
+    }
+    {
+        /* Test vector 6 */
+        const unsigned char pk6[33] = {
+            0x03, 0xFA, 0xC2, 0x11, 0x4C, 0x2F, 0xBB, 0x09,
+            0x15, 0x27, 0xEB, 0x7C, 0x64, 0xEC, 0xB1, 0x1F,
+            0x80, 0x21, 0xCB, 0x45, 0xE8, 0xE7, 0x80, 0x9D,
+            0x3C, 0x09, 0x38, 0xE4, 0xB8, 0xC0, 0xE5, 0xF8,
+            0x4B
+        };
+        const unsigned char msg6[32] = {
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
+        };
+        const unsigned char sig6[64] = {
+            0x57, 0x0D, 0xD4, 0xCA, 0x83, 0xD4, 0xE6, 0x31,
+            0x7B, 0x8E, 0xE6, 0xBA, 0xE8, 0x34, 0x67, 0xA1,
+            0xBF, 0x41, 0x9D, 0x07, 0x67, 0x12, 0x2D, 0xE4,
+            0x09, 0x39, 0x44, 0x14, 0xB0, 0x50, 0x80, 0xDC,
+            0xE9, 0xEE, 0x5F, 0x23, 0x7C, 0xBD, 0x10, 0x8E,
+            0xAB, 0xAE, 0x1E, 0x37, 0x75, 0x9A, 0xE4, 0x7F,
+            0x8E, 0x42, 0x03, 0xDA, 0x35, 0x32, 0xEB, 0x28,
+            0xDB, 0x86, 0x0F, 0x33, 0xD6, 0x2D, 0x49, 0xBD
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk6, msg6, sig6, 1);
+    }
+    {
+        /* Test vector 7 */
+        const unsigned char pk7[33] = {
+            0x03, 0xEE, 0xFD, 0xEA, 0x4C, 0xDB, 0x67, 0x77,
+            0x50, 0xA4, 0x20, 0xFE, 0xE8, 0x07, 0xEA, 0xCF,
+            0x21, 0xEB, 0x98, 0x98, 0xAE, 0x79, 0xB9, 0x76,
+            0x87, 0x66, 0xE4, 0xFA, 0xA0, 0x4A, 0x2D, 0x4A,
+            0x34
+        };
+        secp256k1_pubkey pk7_parsed;
+        /* No need to check the signature of the test vector as parsing the pubkey already fails */
+        CHECK(!secp256k1_ec_pubkey_parse(ctx, &pk7_parsed, pk7, 33));
+    }
+    {
+        /* Test vector 8 */
+        const unsigned char pk8[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg8[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig8[64] = {
+            0x2A, 0x29, 0x8D, 0xAC, 0xAE, 0x57, 0x39, 0x5A,
+            0x15, 0xD0, 0x79, 0x5D, 0xDB, 0xFD, 0x1D, 0xCB,
+            0x56, 0x4D, 0xA8, 0x2B, 0x0F, 0x26, 0x9B, 0xC7,
+            0x0A, 0x74, 0xF8, 0x22, 0x04, 0x29, 0xBA, 0x1D,
+            0xFA, 0x16, 0xAE, 0xE0, 0x66, 0x09, 0x28, 0x0A,
+            0x19, 0xB6, 0x7A, 0x24, 0xE1, 0x97, 0x7E, 0x46,
+            0x97, 0x71, 0x2B, 0x5F, 0xD2, 0x94, 0x39, 0x14,
+            0xEC, 0xD5, 0xF7, 0x30, 0x90, 0x1B, 0x4A, 0xB7
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk8, msg8, sig8, 0);
+    }
+    {
+        /* Test vector 9 */
+        const unsigned char pk9[33] = {
+            0x03, 0xFA, 0xC2, 0x11, 0x4C, 0x2F, 0xBB, 0x09,
+            0x15, 0x27, 0xEB, 0x7C, 0x64, 0xEC, 0xB1, 0x1F,
+            0x80, 0x21, 0xCB, 0x45, 0xE8, 0xE7, 0x80, 0x9D,
+            0x3C, 0x09, 0x38, 0xE4, 0xB8, 0xC0, 0xE5, 0xF8,
+            0x4B
+        };
+        const unsigned char msg9[32] = {
+            0x5E, 0x2D, 0x58, 0xD8, 0xB3, 0xBC, 0xDF, 0x1A,
+            0xBA, 0xDE, 0xC7, 0x82, 0x90, 0x54, 0xF9, 0x0D,
+            0xDA, 0x98, 0x05, 0xAA, 0xB5, 0x6C, 0x77, 0x33,
+            0x30, 0x24, 0xB9, 0xD0, 0xA5, 0x08, 0xB7, 0x5C
+        };
+        const unsigned char sig9[64] = {
+            0x00, 0xDA, 0x9B, 0x08, 0x17, 0x2A, 0x9B, 0x6F,
+            0x04, 0x66, 0xA2, 0xDE, 0xFD, 0x81, 0x7F, 0x2D,
+            0x7A, 0xB4, 0x37, 0xE0, 0xD2, 0x53, 0xCB, 0x53,
+            0x95, 0xA9, 0x63, 0x86, 0x6B, 0x35, 0x74, 0xBE,
+            0xD0, 0x92, 0xF9, 0xD8, 0x60, 0xF1, 0x77, 0x6A,
+            0x1F, 0x74, 0x12, 0xAD, 0x8A, 0x1E, 0xB5, 0x0D,
+            0xAC, 0xCC, 0x22, 0x2B, 0xC8, 0xC0, 0xE2, 0x6B,
+            0x20, 0x56, 0xDF, 0x2F, 0x27, 0x3E, 0xFD, 0xEC
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk9, msg9, sig9, 0);
+    }
+    {
+        /* Test vector 10 */
+        const unsigned char pk10[33] = {
+            0x02, 0x79, 0xBE, 0x66, 0x7E, 0xF9, 0xDC, 0xBB,
+            0xAC, 0x55, 0xA0, 0x62, 0x95, 0xCE, 0x87, 0x0B,
+            0x07, 0x02, 0x9B, 0xFC, 0xDB, 0x2D, 0xCE, 0x28,
+            0xD9, 0x59, 0xF2, 0x81, 0x5B, 0x16, 0xF8, 0x17,
+            0x98
+        };
+        const unsigned char msg10[32] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+        };
+        const unsigned char sig10[64] = {
+            0x78, 0x7A, 0x84, 0x8E, 0x71, 0x04, 0x3D, 0x28,
+            0x0C, 0x50, 0x47, 0x0E, 0x8E, 0x15, 0x32, 0xB2,
+            0xDD, 0x5D, 0x20, 0xEE, 0x91, 0x2A, 0x45, 0xDB,
+            0xDD, 0x2B, 0xD1, 0xDF, 0xBF, 0x18, 0x7E, 0xF6,
+            0x8F, 0xCE, 0x56, 0x77, 0xCE, 0x7A, 0x62, 0x3C,
+            0xB2, 0x00, 0x11, 0x22, 0x57, 0x97, 0xCE, 0x7A,
+            0x8D, 0xE1, 0xDC, 0x6C, 0xCD, 0x4F, 0x75, 0x4A,
+            0x47, 0xDA, 0x6C, 0x60, 0x0E, 0x59, 0x54, 0x3C
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk10, msg10, sig10, 0);
+    }
+    {
+        /* Test vector 11 */
+        const unsigned char pk11[33] = {
+            0x03, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg11[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig11[64] = {
+            0x2A, 0x29, 0x8D, 0xAC, 0xAE, 0x57, 0x39, 0x5A,
+            0x15, 0xD0, 0x79, 0x5D, 0xDB, 0xFD, 0x1D, 0xCB,
+            0x56, 0x4D, 0xA8, 0x2B, 0x0F, 0x26, 0x9B, 0xC7,
+            0x0A, 0x74, 0xF8, 0x22, 0x04, 0x29, 0xBA, 0x1D,
+            0x1E, 0x51, 0xA2, 0x2C, 0xCE, 0xC3, 0x55, 0x99,
+            0xB8, 0xF2, 0x66, 0x91, 0x22, 0x81, 0xF8, 0x36,
+            0x5F, 0xFC, 0x2D, 0x03, 0x5A, 0x23, 0x04, 0x34,
+            0xA1, 0xA6, 0x4D, 0xC5, 0x9F, 0x70, 0x13, 0xFD
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk11, msg11, sig11, 0);
+    }
+    {
+        /* Test vector 12 */
+        const unsigned char pk12[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg12[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig12[64] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x9E, 0x9D, 0x01, 0xAF, 0x98, 0x8B, 0x5C, 0xED,
+            0xCE, 0x47, 0x22, 0x1B, 0xFA, 0x9B, 0x22, 0x27,
+            0x21, 0xF3, 0xFA, 0x40, 0x89, 0x15, 0x44, 0x4A,
+            0x4B, 0x48, 0x90, 0x21, 0xDB, 0x55, 0x77, 0x5F
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk12, msg12, sig12, 0);
+    }
+    {
+        /* Test vector 13 */
+        const unsigned char pk13[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg13[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig13[64] = {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+            0xD3, 0x7D, 0xDF, 0x02, 0x54, 0x35, 0x18, 0x36,
+            0xD8, 0x4B, 0x1B, 0xD6, 0xA7, 0x95, 0xFD, 0x5D,
+            0x52, 0x30, 0x48, 0xF2, 0x98, 0xC4, 0x21, 0x4D,
+            0x18, 0x7F, 0xE4, 0x89, 0x29, 0x47, 0xF7, 0x28
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk13, msg13, sig13, 0);
+    }
+    {
+        /* Test vector 14 */
+        const unsigned char pk14[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg14[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x14, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig14[64] = {
+            0x4A, 0x29, 0x8D, 0xAC, 0xAE, 0x57, 0x39, 0x5A,
+            0x15, 0xD0, 0x79, 0x5D, 0xDB, 0xFD, 0x1D, 0xCB,
+            0x56, 0x4D, 0xA8, 0x2B, 0x0F, 0x26, 0x9B, 0xC7,
+            0x0A, 0x74, 0xF8, 0x22, 0x04, 0x29, 0xBA, 0x1D,
+            0x1E, 0x51, 0xA2, 0x2C, 0xCE, 0xC3, 0x55, 0x99,
+            0xB8, 0xF2, 0x66, 0x91, 0x22, 0x81, 0xF8, 0x36,
+            0x5F, 0xFC, 0x2D, 0x03, 0x5A, 0x23, 0x04, 0x34,
+            0xA1, 0xA6, 0x4D, 0xC5, 0x9F, 0x70, 0x13, 0xFD
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk14, msg14, sig14, 0);
+    }
+    {
+        /* Test vector 15 */
+        const unsigned char pk15[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg15[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig15[64] = {
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFC, 0x2F,
+            0x1E, 0x51, 0xA2, 0x2C, 0xCE, 0xC3, 0x55, 0x99,
+            0xB8, 0xF2, 0x66, 0x91, 0x22, 0x81, 0xF8, 0x36,
+            0x5F, 0xFC, 0x2D, 0x03, 0x5A, 0x23, 0x04, 0x34,
+            0xA1, 0xA6, 0x4D, 0xC5, 0x9F, 0x70, 0x13, 0xFD
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk15, msg15, sig15, 0);
+    }
+    {
+        /* Test vector 16 */
+        const unsigned char pk16[33] = {
+            0x02, 0xDF, 0xF1, 0xD7, 0x7F, 0x2A, 0x67, 0x1C,
+            0x5F, 0x36, 0x18, 0x37, 0x26, 0xDB, 0x23, 0x41,
+            0xBE, 0x58, 0xFE, 0xAE, 0x1D, 0xA2, 0xDE, 0xCE,
+            0xD8, 0x43, 0x24, 0x0F, 0x7B, 0x50, 0x2B, 0xA6,
+            0x59
+        };
+        const unsigned char msg16[32] = {
+            0x24, 0x3F, 0x6A, 0x88, 0x85, 0xA3, 0x08, 0xD3,
+            0x13, 0x19, 0x8A, 0x2E, 0x03, 0x70, 0x73, 0x44,
+            0xA4, 0x09, 0x38, 0x22, 0x29, 0x9F, 0x31, 0xD0,
+            0x08, 0x2E, 0xFA, 0x98, 0xEC, 0x4E, 0x6C, 0x89
+        };
+        const unsigned char sig16[64] = {
+            0x2A, 0x29, 0x8D, 0xAC, 0xAE, 0x57, 0x39, 0x5A,
+            0x15, 0xD0, 0x79, 0x5D, 0xDB, 0xFD, 0x1D, 0xCB,
+            0x56, 0x4D, 0xA8, 0x2B, 0x0F, 0x26, 0x9B, 0xC7,
+            0x0A, 0x74, 0xF8, 0x22, 0x04, 0x29, 0xBA, 0x1D,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFE,
+            0xBA, 0xAE, 0xDC, 0xE6, 0xAF, 0x48, 0xA0, 0x3B,
+            0xBF, 0xD2, 0x5E, 0x8C, 0xD0, 0x36, 0x41, 0x41
+        };
+        test_schnorrsig_bip_vectors_check_verify(scratch, pk16, msg16, sig16, 0);
+    }
+}
+
+/* Nonce function that returns constant 0 */
+static int nonce_function_failing(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
+    (void) msg32;
+    (void) key32;
+    (void) algo16;
+    (void) data;
+    (void) counter;
+    (void) nonce32;
+    return 0;
+}
+
+/* Nonce function that sets nonce to 0 */
+static int nonce_function_0(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
+    (void) msg32;
+    (void) key32;
+    (void) algo16;
+    (void) data;
+    (void) counter;
+
+    memset(nonce32, 0, 32);
+    return 1;
+}
+
+void test_schnorrsig_sign(void) {
+    unsigned char sk[32];
+    const unsigned char msg[32] = "this is a msg for a schnorrsig..";
+    secp256k1_schnorrsig sig;
+
+    memset(sk, 23, sizeof(sk));
+    CHECK(secp256k1_schnorrsig_sign(ctx, &sig, NULL, msg, sk, NULL, NULL) == 1);
+
+    /* Overflowing secret key */
+    memset(sk, 0xFF, sizeof(sk));
+    CHECK(secp256k1_schnorrsig_sign(ctx, &sig, NULL, msg, sk, NULL, NULL) == 0);
+    memset(sk, 23, sizeof(sk));
+
+    CHECK(secp256k1_schnorrsig_sign(ctx, &sig, NULL, msg, sk, nonce_function_failing, NULL) == 0);
+    CHECK(secp256k1_schnorrsig_sign(ctx, &sig, NULL, msg, sk, nonce_function_0, NULL) == 0);
+}
+
+#define N_SIGS  200
+/* Creates N_SIGS valid signatures and verifies them with verify and verify_batch. Then flips some
+ * bits and checks that verification now fails. */
+void test_schnorrsig_sign_verify(secp256k1_scratch_space *scratch) {
+    const unsigned char sk[32] = "shhhhhhhh! this key is a secret.";
+    unsigned char msg[N_SIGS][32];
+    secp256k1_schnorrsig sig[N_SIGS];
+    size_t i;
+    const secp256k1_schnorrsig *sig_arr[N_SIGS];
+    const unsigned char *msg_arr[N_SIGS];
+    const secp256k1_pubkey *pk_arr[N_SIGS];
+    secp256k1_pubkey pk;
+
+    CHECK(secp256k1_ec_pubkey_create(ctx, &pk, sk));
+
+    CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, NULL, NULL, NULL, 0));
+
+    for (i = 0; i < N_SIGS; i++) {
+        secp256k1_rand256(msg[i]);
+        CHECK(secp256k1_schnorrsig_sign(ctx, &sig[i], NULL, msg[i], sk, NULL, NULL));
+        CHECK(secp256k1_schnorrsig_verify(ctx, &sig[i], msg[i], &pk));
+        sig_arr[i] = &sig[i];
+        msg_arr[i] = msg[i];
+        pk_arr[i] = &pk;
+    }
+
+    CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 1));
+    CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 2));
+    CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 4));
+    CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, N_SIGS));
+
+    {
+        /* Flip a few bits in the signature and in the message and check that
+         * verify and verify_batch fail */
+        size_t sig_idx = secp256k1_rand_int(4);
+        size_t byte_idx = secp256k1_rand_int(32);
+        unsigned char xorbyte = secp256k1_rand_int(254)+1;
+        sig[sig_idx].data[byte_idx] ^= xorbyte;
+        CHECK(!secp256k1_schnorrsig_verify(ctx, &sig[sig_idx], msg[sig_idx], &pk));
+        CHECK(!secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 4));
+        sig[sig_idx].data[byte_idx] ^= xorbyte;
+
+        byte_idx = secp256k1_rand_int(32);
+        sig[sig_idx].data[32+byte_idx] ^= xorbyte;
+        CHECK(!secp256k1_schnorrsig_verify(ctx, &sig[sig_idx], msg[sig_idx], &pk));
+        CHECK(!secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 4));
+        sig[sig_idx].data[32+byte_idx] ^= xorbyte;
+
+        byte_idx = secp256k1_rand_int(32);
+        msg[sig_idx][byte_idx] ^= xorbyte;
+        CHECK(!secp256k1_schnorrsig_verify(ctx, &sig[sig_idx], msg[sig_idx], &pk));
+        CHECK(!secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 4));
+        msg[sig_idx][byte_idx] ^= xorbyte;
+
+        /* Check that above bitflips have been reversed correctly */
+        CHECK(secp256k1_schnorrsig_verify(ctx, &sig[sig_idx], msg[sig_idx], &pk));
+        CHECK(secp256k1_schnorrsig_verify_batch(ctx, scratch, sig_arr, msg_arr, pk_arr, 4));
+    }
+}
+#undef N_SIGS
+
+void run_schnorrsig_tests(void) {
+    secp256k1_scratch_space *scratch = secp256k1_scratch_space_create(ctx, 1024 * 1024);
+
+    test_schnorrsig_serialize();
+    test_schnorrsig_api(scratch);
+    test_schnorrsig_bip_vectors(scratch);
+    test_schnorrsig_sign();
+    test_schnorrsig_sign_verify(scratch);
+
+    secp256k1_scratch_space_destroy(scratch);
+}
+
+#endif

src/modules/surjection/Makefile.am.include

@@ -0,0 +1,6 @@
+include_HEADERS += include/secp256k1_surjectionproof.h
+noinst_HEADERS += src/modules/surjection/main_impl.h
+noinst_HEADERS += src/modules/surjection/surjection.h
+noinst_HEADERS += src/modules/surjection/surjection_impl.h
+noinst_HEADERS += src/modules/surjection/tests_impl.h
+

src/modules/surjection/main_impl.h

@@ -0,0 +1,380 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+#ifndef SECP256K1_MODULE_SURJECTION_MAIN
+#define SECP256K1_MODULE_SURJECTION_MAIN
+
+#include <assert.h>
+#include <string.h>
+
+#include "modules/rangeproof/borromean.h"
+#include "modules/surjection/surjection_impl.h"
+#include "hash.h"
+#include "include/secp256k1_rangeproof.h"
+#include "include/secp256k1_surjectionproof.h"
+
+static size_t secp256k1_count_bits_set(const unsigned char* data, size_t count) {
+    size_t ret = 0;
+    size_t i;
+    for (i = 0; i < count; i++) {
+#ifdef HAVE_BUILTIN_POPCOUNT
+	ret += __builtin_popcount(data[i]);
+#else
+        ret += !!(data[i] & 0x1);
+        ret += !!(data[i] & 0x2);
+        ret += !!(data[i] & 0x4);
+        ret += !!(data[i] & 0x8);
+        ret += !!(data[i] & 0x10);
+        ret += !!(data[i] & 0x20);
+        ret += !!(data[i] & 0x40);
+        ret += !!(data[i] & 0x80);
+#endif
+    }
+    return ret;
+}
+
+int secp256k1_surjectionproof_parse(const secp256k1_context* ctx, secp256k1_surjectionproof *proof, const unsigned char *input, size_t inputlen) {
+    size_t n_inputs;
+    size_t signature_len;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(input != NULL);
+    (void) ctx;
+
+    if (inputlen < 2) {
+        return 0;
+    }
+    n_inputs = ((size_t) (input[1] << 8)) + input[0];
+    if (n_inputs > SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS) {
+        return 0;
+    }
+    if (inputlen < 2 + (n_inputs + 7) / 8) {
+        return 0;
+    }
+
+    signature_len = 32 * (1 + secp256k1_count_bits_set(&input[2], (n_inputs + 7) / 8));
+    if (inputlen != 2 + (n_inputs + 7) / 8 + signature_len) {
+        return 0;
+    }
+    proof->n_inputs = n_inputs;
+    memcpy(proof->used_inputs, &input[2], (n_inputs + 7) / 8);
+    memcpy(proof->data, &input[2 + (n_inputs + 7) / 8], signature_len);
+
+    return 1;
+}
+
+int secp256k1_surjectionproof_serialize(const secp256k1_context* ctx, unsigned char *output, size_t *outputlen, const secp256k1_surjectionproof *proof) {
+    size_t signature_len;
+    size_t serialized_len;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(output != NULL);
+    ARG_CHECK(outputlen != NULL);
+    ARG_CHECK(proof != NULL);
+    (void) ctx;
+
+    signature_len = 32 * (1 + secp256k1_count_bits_set(proof->used_inputs, (proof->n_inputs + 7) / 8));
+    serialized_len = 2 + (proof->n_inputs + 7) / 8 + signature_len;
+    if (*outputlen < serialized_len) {
+        return 0;
+    }
+
+    output[0] = proof->n_inputs % 0x100;
+    output[1] = proof->n_inputs / 0x100;
+    memcpy(&output[2], proof->used_inputs, (proof->n_inputs + 7) / 8);
+    memcpy(&output[2 + (proof->n_inputs + 7) / 8], proof->data, signature_len);
+    *outputlen = serialized_len;
+
+    return 1;
+}
+
+size_t secp256k1_surjectionproof_n_total_inputs(const secp256k1_context* ctx, const secp256k1_surjectionproof* proof) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    (void) ctx;
+    return proof->n_inputs;
+}
+
+size_t secp256k1_surjectionproof_n_used_inputs(const secp256k1_context* ctx, const secp256k1_surjectionproof* proof) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    (void) ctx;
+    return secp256k1_count_bits_set(proof->used_inputs, (proof->n_inputs + 7) / 8);
+}
+
+size_t secp256k1_surjectionproof_serialized_size(const secp256k1_context* ctx, const secp256k1_surjectionproof* proof) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    return 2 + (proof->n_inputs + 7) / 8 + 32 * (1 + secp256k1_surjectionproof_n_used_inputs(ctx, proof));
+}
+
+typedef struct {
+    unsigned char state[32];
+    size_t state_i;
+} secp256k1_surjectionproof_csprng;
+
+static void secp256k1_surjectionproof_csprng_init(secp256k1_surjectionproof_csprng *csprng, const unsigned char* state) {
+    memcpy(csprng->state, state, 32);
+    csprng->state_i = 0;
+}
+
+static size_t secp256k1_surjectionproof_csprng_next(secp256k1_surjectionproof_csprng *csprng, size_t rand_max) {
+    /* The number of random bytes to read for each random sample */
+    const size_t increment = rand_max > 256 ? 2 : 1;
+    /* The maximum value expressable by the number of random bytes we read */
+    const size_t selection_range = rand_max > 256 ? 0xffff : 0xff;
+    /* The largest multiple of rand_max that fits within selection_range */
+    const size_t limit = ((selection_range + 1) / rand_max) * rand_max;
+
+    while (1) {
+        size_t val;
+        if (csprng->state_i + increment >= 32) {
+            secp256k1_sha256 sha;
+            secp256k1_sha256_initialize(&sha);
+            secp256k1_sha256_write(&sha, csprng->state, 32);
+            secp256k1_sha256_finalize(&sha, csprng->state);
+            csprng->state_i = 0;
+        }
+        val = csprng->state[csprng->state_i];
+        if (increment > 1) {
+            val = (val << 8) + csprng->state[csprng->state_i + 1];
+        }
+        csprng->state_i += increment;
+        /* Accept only values below our limit. Values equal to or above the limit are
+         * biased because they comprise only a subset of the range (0, rand_max - 1) */
+        if (val < limit) {
+            return val % rand_max;
+        }
+    }
+}
+
+/* While '_allocate_initialized' may be a wordy suffix for this function, and '_create'
+ * may have been more appropriate, '_create' could be confused with '_generate',
+ * as the meanings for the words are close. Therefore, more wordy, but less
+ * ambiguous suffix was chosen. */
+int secp256k1_surjectionproof_allocate_initialized(const secp256k1_context* ctx, secp256k1_surjectionproof** proof_out_p, size_t *input_index, const secp256k1_fixed_asset_tag* fixed_input_tags, const size_t n_input_tags, const size_t n_input_tags_to_use, const secp256k1_fixed_asset_tag* fixed_output_tag, const size_t n_max_iterations, const unsigned char *random_seed32) {
+    int ret = 0;
+    secp256k1_surjectionproof* proof;
+
+    VERIFY_CHECK(ctx != NULL);
+
+    ARG_CHECK(proof_out_p != NULL);
+    *proof_out_p = 0;
+
+    proof = (secp256k1_surjectionproof*)checked_malloc(&ctx->error_callback, sizeof(secp256k1_surjectionproof));
+    if (proof != NULL) {
+        ret = secp256k1_surjectionproof_initialize(ctx, proof, input_index, fixed_input_tags, n_input_tags, n_input_tags_to_use, fixed_output_tag, n_max_iterations, random_seed32);
+        if (ret) {
+            *proof_out_p = proof;
+        }
+        else {
+            free(proof);
+        }
+    }
+    return ret;
+}
+
+/* secp256k1_surjectionproof structure may also be allocated on the stack,
+ * and initialized explicitly via secp256k1_surjectionproof_initialize().
+ * Supplying stack-allocated struct to _destroy() will result in calling
+ * free() with the pointer that points at the stack, with disasterous
+ * consequences. Thus, it is not advised to mix heap- and stack-allocating
+ * approaches to working with this struct. It is possible to detect this
+ * situation by using additional field in the struct that can be set to
+ * special value depending on the allocation path, and check it here.
+ * But currently, it is not seen as big enough concern to warrant this extra code .*/
+void secp256k1_surjectionproof_destroy(secp256k1_surjectionproof* proof) {
+    if (proof != NULL) {
+        VERIFY_CHECK(proof->n_inputs <= SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS);
+        free(proof);
+    }
+}
+
+int secp256k1_surjectionproof_initialize(const secp256k1_context* ctx, secp256k1_surjectionproof* proof, size_t *input_index, const secp256k1_fixed_asset_tag* fixed_input_tags, const size_t n_input_tags, const size_t n_input_tags_to_use, const secp256k1_fixed_asset_tag* fixed_output_tag, const size_t n_max_iterations, const unsigned char *random_seed32) {
+    secp256k1_surjectionproof_csprng csprng;
+    size_t n_iterations = 0;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(input_index != NULL);
+    ARG_CHECK(fixed_input_tags != NULL);
+    ARG_CHECK(fixed_output_tag != NULL);
+    ARG_CHECK(random_seed32 != NULL);
+    ARG_CHECK(n_input_tags <= SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS);
+    ARG_CHECK(n_input_tags_to_use <= n_input_tags);
+    (void) ctx;
+
+    secp256k1_surjectionproof_csprng_init(&csprng, random_seed32);
+    memset(proof->data, 0, sizeof(proof->data));
+    proof->n_inputs = n_input_tags;
+
+    while (1) {
+        int has_output_tag = 0;
+        size_t i;
+
+        /* obtain a random set of indices */
+        memset(proof->used_inputs, 0, sizeof(proof->used_inputs));
+        for (i = 0; i < n_input_tags_to_use; i++) {
+            while (1) {
+                size_t next_input_index;
+                next_input_index = secp256k1_surjectionproof_csprng_next(&csprng, n_input_tags);
+                if (memcmp(&fixed_input_tags[next_input_index], fixed_output_tag, sizeof(*fixed_output_tag)) == 0) {
+                    *input_index = next_input_index;
+                    has_output_tag = 1;
+                }
+
+                if (!(proof->used_inputs[next_input_index / 8] & (1 << (next_input_index  % 8)))) {
+                    proof->used_inputs[next_input_index / 8] |= (1 << (next_input_index % 8));
+                    break;
+                }
+            }
+        }
+
+        /* Check if we succeeded */
+        n_iterations++;
+        if (has_output_tag) {
+#ifdef VERIFY
+            proof->initialized = 1;
+#endif
+            return n_iterations;
+        }
+        if (n_iterations >= n_max_iterations) {
+#ifdef VERIFY
+            proof->initialized = 0;
+#endif
+            return 0;
+        }
+    }
+}
+
+int secp256k1_surjectionproof_generate(const secp256k1_context* ctx, secp256k1_surjectionproof* proof, const secp256k1_generator* ephemeral_input_tags, size_t n_ephemeral_input_tags, const secp256k1_generator* ephemeral_output_tag, size_t input_index, const unsigned char *input_blinding_key, const unsigned char *output_blinding_key) {
+    secp256k1_scalar blinding_key;
+    secp256k1_scalar tmps;
+    secp256k1_scalar nonce;
+    int overflow = 0;
+    size_t rsizes[1];    /* array needed for borromean sig API */
+    size_t indices[1];   /* array needed for borromean sig API */
+    size_t i;
+    size_t n_total_pubkeys;
+    size_t n_used_pubkeys;
+    size_t ring_input_index = 0;
+    secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_ge inputs[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_ge output;
+    unsigned char msg32[32];
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(ephemeral_input_tags != NULL);
+    ARG_CHECK(ephemeral_output_tag != NULL);
+    ARG_CHECK(input_blinding_key != NULL);
+    ARG_CHECK(output_blinding_key != NULL);
+#ifdef VERIFY
+    CHECK(proof->initialized == 1);
+#endif
+
+    /* Compute secret key */
+    secp256k1_scalar_set_b32(&tmps, input_blinding_key, &overflow);
+    if (overflow) {
+        return 0;
+    }
+    secp256k1_scalar_set_b32(&blinding_key, output_blinding_key, &overflow);
+    if (overflow) {
+        return 0;
+    }
+    /* The only time the input may equal the output is if neither one was blinded in the first place,
+     * i.e. both blinding keys are zero. Otherwise this is a privacy leak. */
+    if (secp256k1_scalar_eq(&tmps, &blinding_key) && !secp256k1_scalar_is_zero(&blinding_key)) {
+        return 0;
+    }
+    secp256k1_scalar_negate(&tmps, &tmps);
+    secp256k1_scalar_add(&blinding_key, &blinding_key, &tmps);
+
+    /* Compute public keys */
+    n_total_pubkeys = secp256k1_surjectionproof_n_total_inputs(ctx, proof);
+    n_used_pubkeys = secp256k1_surjectionproof_n_used_inputs(ctx, proof);
+    if (n_used_pubkeys > n_total_pubkeys || n_total_pubkeys != n_ephemeral_input_tags) {
+        return 0;
+    }
+
+    secp256k1_generator_load(&output, ephemeral_output_tag);
+    for (i = 0; i < n_total_pubkeys; i++) {
+        secp256k1_generator_load(&inputs[i], &ephemeral_input_tags[i]);
+    }
+
+    secp256k1_surjection_compute_public_keys(ring_pubkeys, n_used_pubkeys, inputs, n_total_pubkeys, proof->used_inputs, &output, input_index, &ring_input_index);
+
+    /* Produce signature */
+    rsizes[0] = (int) n_used_pubkeys;
+    indices[0] = (int) ring_input_index;
+    secp256k1_surjection_genmessage(msg32, inputs, n_total_pubkeys, &output);
+    if (secp256k1_surjection_genrand(borromean_s, n_used_pubkeys, &blinding_key) == 0) {
+        return 0;
+    }
+    /* Borromean sign will overwrite one of the s values we just generated, so use
+     * it as a nonce instead. This avoids extra random generation and also is an
+     * homage to the rangeproof code which does this very cleverly to encode messages. */
+    nonce = borromean_s[ring_input_index];
+    secp256k1_scalar_clear(&borromean_s[ring_input_index]);
+    if (secp256k1_borromean_sign(&ctx->ecmult_ctx, &ctx->ecmult_gen_ctx, &proof->data[0], borromean_s, ring_pubkeys, &nonce, &blinding_key, rsizes, indices, 1, msg32, 32) == 0) {
+        return 0;
+    }
+    for (i = 0; i < n_used_pubkeys; i++) {
+        secp256k1_scalar_get_b32(&proof->data[32 + 32 * i], &borromean_s[i]);
+    }
+    return 1;
+}
+
+int secp256k1_surjectionproof_verify(const secp256k1_context* ctx, const secp256k1_surjectionproof* proof, const secp256k1_generator* ephemeral_input_tags, size_t n_ephemeral_input_tags, const secp256k1_generator* ephemeral_output_tag) {
+    size_t rsizes[1];    /* array needed for borromean sig API */
+    size_t i;
+    size_t n_total_pubkeys;
+    size_t n_used_pubkeys;
+    secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_ge inputs[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
+    secp256k1_ge output;
+    unsigned char msg32[32];
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(proof != NULL);
+    ARG_CHECK(ephemeral_input_tags != NULL);
+    ARG_CHECK(ephemeral_output_tag != NULL);
+
+    /* Compute public keys */
+    n_total_pubkeys = secp256k1_surjectionproof_n_total_inputs(ctx, proof);
+    n_used_pubkeys = secp256k1_surjectionproof_n_used_inputs(ctx, proof);
+    if (n_used_pubkeys == 0 || n_used_pubkeys > n_total_pubkeys || n_total_pubkeys != n_ephemeral_input_tags) {
+        return 0;
+    }
+
+    secp256k1_generator_load(&output, ephemeral_output_tag);
+    for (i = 0; i < n_total_pubkeys; i++) {
+        secp256k1_generator_load(&inputs[i], &ephemeral_input_tags[i]);
+    }
+
+    if (secp256k1_surjection_compute_public_keys(ring_pubkeys, n_used_pubkeys, inputs, n_total_pubkeys, proof->used_inputs, &output, 0, NULL) == 0) {
+        return 0;
+    }
+
+    /* Verify signature */
+    rsizes[0] = (int) n_used_pubkeys;
+    for (i = 0; i < n_used_pubkeys; i++) {
+        int overflow = 0;
+        secp256k1_scalar_set_b32(&borromean_s[i], &proof->data[32 + 32 * i], &overflow);
+        if (overflow == 1) {
+            return 0;
+        }
+    }
+    secp256k1_surjection_genmessage(msg32, inputs, n_total_pubkeys, &output);
+    return secp256k1_borromean_verify(&ctx->ecmult_ctx, NULL, &proof->data[0], borromean_s, ring_pubkeys, rsizes, 1, msg32, 32);
+}
+
+#endif

src/modules/surjection/surjection.h

@@ -0,0 +1,19 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_SURJECTION_H_
+#define _SECP256K1_SURJECTION_H_
+
+#include "group.h"
+#include "scalar.h"
+
+SECP256K1_INLINE static int secp256k1_surjection_genmessage(unsigned char *msg32, secp256k1_ge *ephemeral_input_tags, size_t n_input_tags, secp256k1_ge *ephemeral_output_tag);
+
+SECP256K1_INLINE static int secp256k1_surjection_genrand(secp256k1_scalar *s, size_t ns, const secp256k1_scalar *blinding_key);
+
+SECP256K1_INLINE static int secp256k1_surjection_compute_public_keys(secp256k1_gej *pubkeys, size_t n_pubkeys, const secp256k1_ge *input_tags, size_t n_input_tags, const unsigned char *used_tags, const secp256k1_ge *output_tag, size_t input_index, size_t *ring_input_index);
+
+#endif

src/modules/surjection/surjection.md

@@ -0,0 +1,108 @@
+Surjection Proof Module
+===========================
+
+This module implements a scheme by which a given point can be proven to be
+equal to one of a set of points, plus a known difference. This is used in
+Confidential Assets when reblinding "asset commitments", which are NUMS
+points, to prove that the underlying NUMS point does not change during
+reblinding.
+
+Assets are represented, in general, by a 32-byte seed (a hash of some
+transaction data) which is hashed to form a NUMS generator, which appears
+on the blockchain only in blinded form. We refer to the seed as an
+"asset ID" and the blinded generator as an "(ephemeral) asset commitment".
+These asset commitments are unique per-output, and their NUMS components
+are in general known only to the holder of the output.
+
+The result is that within a transaction, all outputs are able to have
+a new uniformly-random asset commitment which cannot be associated with
+any individual input asset id, but verifiers are nonetheless assured that
+all assets coming out of a transaction are ones that went in.
+
+### Terminology
+
+Assets are identified by a 32-byte "asset ID". In this library these IDs
+are used as input to a point-valued hash function `H`. We usually refer
+to the hash output as `A`, since this output is the only thing that appears
+in the algebra.
+
+Then transaction outputs have "asset commitments", which are curvepoints
+of the form `A + rG`, where `A` is the hash of the asset ID and `r` is
+some random "blinding factor".
+
+### Design Rationale
+
+Confidential Assets essentially works by replacing the second NUMS generator
+`H` in Confidental Transactions with a per-asset unique NUMS generator. This
+allows the same verification equation (the sum of all blinded inputs must
+equal the sum of all blinded outputs) to imply that quantity of *every* asset
+type is preserved in each transaction.
+
+It turns out that even if outputs are reblinded by the addition of `rG` for
+some known `r`, this verification equation has the same meaning, with one
+caveat: verifiers must be assured that the reblinding preserves the original
+generators (and does not, for example, negate them).
+
+This assurance is what surjection proofs provide.
+
+### Limitations
+
+The naive scheme works as follows: every output asset is shown to have come
+from some input asset. However, the proofs scale with the number of input
+assets, so for all outputs the total size of all surjection proofs is `O(mn)`
+for `m`, `n` the number of inputs and outputs.
+
+We therefore restrict the number of inputs that each output may have come
+from to 3 (well, some fixed number, which is passed into the API), which
+provides a weaker form of blinding, but gives `O(n)` scaling. Over many
+transactions, the privacy afforded by this increases exponentially.
+
+### Our Scheme
+
+Our scheme works as follows. Proofs are generated in two steps, "initialization"
+which selects a subset of inputs and "generation" which does the mathematical
+part of proof generation.
+
+Every input has an asset commitment for which we know the blinding key and
+underlying asset ID.
+
+#### Initialization
+
+The initialization function takes a list of input asset IDs and one output
+asset ID. It chooses an input subset of some fixed size repeatedly until it
+the output ID appears at least once in its subset.
+
+It stores a bitmap representing this subset in the proof object and returns
+the number of iterations it needed to choose the subset. The reciprocal of
+this represents the probability that a uniformly random input-output
+mapping would correspond to the actual input-output mapping, and therefore
+gives a measure of privacy. (Lower iteration counts are better.)
+
+It also informs the caller the index of the input whose ID matches the output.
+
+As the API works on only a single output at a time, the total probability
+should be computed by multiplying together the counts for each output.
+
+#### Generation
+
+The generation function takes a list of input asset commitments, an output
+asset commitment, the input index returned by the initialization step, and
+blinding keys for (a) the output commitment, (b) the input commitment. Here
+"the input commitment" refers specifically to the input whose index was
+chosen during initialization.
+
+Next, it computes a ring signature over the differences between the output
+commitment and every input commitment chosen during initialization. Since
+the discrete log of one of these is the difference between the output and
+input blinding keys, it is possible to create a ring signature over every
+differences will be the blinding factor of the output. We create such a
+signature, which completes the proof.
+
+#### Verification
+
+Verification takes a surjection proof object, a list of input commitments,
+and an output commitment. The proof object contains a ring signature and
+a bitmap describing which input commitments to use, and verification
+succeeds iff the signature verifies.
+
+

src/modules/surjection/surjection_impl.h

@@ -0,0 +1,86 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_SURJECTION_IMPL_H_
+#define _SECP256K1_SURJECTION_IMPL_H_
+
+#include <assert.h>
+#include <string.h>
+
+#include "eckey.h"
+#include "group.h"
+#include "scalar.h"
+#include "hash.h"
+
+SECP256K1_INLINE static void secp256k1_surjection_genmessage(unsigned char *msg32, secp256k1_ge *ephemeral_input_tags, size_t n_input_tags, secp256k1_ge *ephemeral_output_tag) {
+    /* compute message */
+    size_t i;
+    unsigned char pk_ser[33];
+    size_t pk_len = sizeof(pk_ser);
+    secp256k1_sha256 sha256_en;
+
+    secp256k1_sha256_initialize(&sha256_en);
+    for (i = 0; i < n_input_tags; i++) {
+        secp256k1_eckey_pubkey_serialize(&ephemeral_input_tags[i], pk_ser, &pk_len, 1);
+        assert(pk_len == sizeof(pk_ser));
+        secp256k1_sha256_write(&sha256_en, pk_ser, pk_len);
+    }
+    secp256k1_eckey_pubkey_serialize(ephemeral_output_tag, pk_ser, &pk_len, 1);
+    assert(pk_len == sizeof(pk_ser));
+    secp256k1_sha256_write(&sha256_en, pk_ser, pk_len);
+    secp256k1_sha256_finalize(&sha256_en, msg32);
+}
+
+SECP256K1_INLINE static int secp256k1_surjection_genrand(secp256k1_scalar *s, size_t ns, const secp256k1_scalar *blinding_key) {
+    size_t i;
+    unsigned char sec_input[36];
+    secp256k1_sha256 sha256_en;
+
+    /* compute s values */
+    secp256k1_scalar_get_b32(&sec_input[4], blinding_key);
+    for (i = 0; i < ns; i++) {
+        int overflow = 0;
+        sec_input[0] = i;
+        sec_input[1] = i >> 8;
+        sec_input[2] = i >> 16;
+        sec_input[3] = i >> 24;
+
+        secp256k1_sha256_initialize(&sha256_en);
+        secp256k1_sha256_write(&sha256_en, sec_input, 36);
+        secp256k1_sha256_finalize(&sha256_en, sec_input);
+        secp256k1_scalar_set_b32(&s[i], sec_input, &overflow);
+        if (overflow == 1) {
+            memset(sec_input, 0, 32);
+            return 0;
+        }
+    }
+    memset(sec_input, 0, 32);
+    return 1;
+}
+
+SECP256K1_INLINE static int secp256k1_surjection_compute_public_keys(secp256k1_gej *pubkeys, size_t n_pubkeys, const secp256k1_ge *input_tags, size_t n_input_tags, const unsigned char *used_tags, const secp256k1_ge *output_tag, size_t input_index, size_t *ring_input_index) {
+    size_t i;
+    size_t j = 0;
+    for (i = 0; i < n_input_tags; i++) {
+        if (used_tags[i / 8] & (1 << (i % 8))) {
+            secp256k1_ge tmpge;
+            secp256k1_ge_neg(&tmpge, &input_tags[i]);
+            secp256k1_gej_set_ge(&pubkeys[j], &tmpge);
+            secp256k1_gej_add_ge_var(&pubkeys[j], &pubkeys[j], output_tag, NULL);
+            if (ring_input_index != NULL && input_index == i) {
+                *ring_input_index = j;
+            }
+            j++;
+            if (j > n_pubkeys) {
+                return 0;
+            }
+        }
+    }
+    return 1;
+}
+
+
+#endif

src/modules/surjection/tests_impl.h

@@ -0,0 +1,535 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_SURJECTIONPROOF_TESTS
+#define SECP256K1_MODULE_SURJECTIONPROOF_TESTS
+
+#include "testrand.h"
+#include "group.h"
+#include "include/secp256k1_generator.h"
+#include "include/secp256k1_rangeproof.h"
+#include "include/secp256k1_surjectionproof.h"
+
+static void test_surjectionproof_api(void) {
+    unsigned char seed[32];
+    secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
+    secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    secp256k1_context *both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+    secp256k1_fixed_asset_tag fixed_input_tags[10];
+    secp256k1_fixed_asset_tag fixed_output_tag;
+    secp256k1_generator ephemeral_input_tags[10];
+    secp256k1_generator ephemeral_output_tag;
+    unsigned char input_blinding_key[10][32];
+    unsigned char output_blinding_key[32];
+    unsigned char serialized_proof[SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX];
+    size_t  serialized_len;
+    secp256k1_surjectionproof proof;
+    secp256k1_surjectionproof* proof_on_heap;
+    size_t n_inputs = sizeof(fixed_input_tags) / sizeof(fixed_input_tags[0]);
+    size_t input_index;
+    int32_t ecount = 0;
+    size_t i;
+
+    secp256k1_rand256(seed);
+    secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_error_callback(both, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(none, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(sign, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(both, counting_illegal_callback_fn, &ecount);
+
+    for (i = 0; i < n_inputs; i++) {
+        secp256k1_rand256(input_blinding_key[i]);
+        secp256k1_rand256(fixed_input_tags[i].data);
+        CHECK(secp256k1_generator_generate_blinded(ctx, &ephemeral_input_tags[i], fixed_input_tags[i].data, input_blinding_key[i]));
+    }
+    secp256k1_rand256(output_blinding_key);
+    memcpy(&fixed_output_tag, &fixed_input_tags[0], sizeof(fixed_input_tags[0]));
+    CHECK(secp256k1_generator_generate_blinded(ctx, &ephemeral_output_tag, fixed_output_tag.data, output_blinding_key));
+
+    /* check allocate_initialized */
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) != 0);
+    CHECK(proof_on_heap != 0);
+    secp256k1_surjectionproof_destroy(proof_on_heap);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, NULL, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, NULL, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, NULL, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS + 1, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, n_inputs, &fixed_input_tags[0], 100, seed) != 0);
+    CHECK(proof_on_heap != 0);
+    secp256k1_surjectionproof_destroy(proof_on_heap);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, n_inputs + 1, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, 3, NULL, 100, seed) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 6);
+    CHECK((secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 0, seed) & 1) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_surjectionproof_allocate_initialized(none, &proof_on_heap, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 100, NULL) == 0);
+    CHECK(proof_on_heap == 0);
+    CHECK(ecount == 7);
+
+    /* we are now going to test essentially the same functions, just without heap allocation.
+     * reset ecount. */
+    ecount = 0;
+
+    /* check initialize */
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) != 0);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_surjectionproof_initialize(none, NULL, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, NULL, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, NULL, n_inputs, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS + 1, 3, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, n_inputs, &fixed_input_tags[0], 100, seed) != 0);
+    CHECK(ecount == 4);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, n_inputs + 1, &fixed_input_tags[0], 100, seed) == 0);
+    CHECK(ecount == 5);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 3, NULL, 100, seed) == 0);
+    CHECK(ecount == 6);
+    CHECK((secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 0, seed) & 1) == 0);
+    CHECK(ecount == 6);
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], 100, NULL) == 0);
+    CHECK(ecount == 7);
+
+    CHECK(secp256k1_surjectionproof_initialize(none, &proof, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[0], 100, seed) != 0);
+    /* check generate */
+    CHECK(secp256k1_surjectionproof_generate(none, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 8);
+    CHECK(secp256k1_surjectionproof_generate(vrfy, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 9);
+
+    CHECK(secp256k1_surjectionproof_generate(sign, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 10);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) != 0);
+    CHECK(ecount == 10);
+
+    CHECK(secp256k1_surjectionproof_generate(both, NULL, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 11);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, NULL, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 12);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs + 1, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 12);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs - 1, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 12);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, 0, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 12);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, NULL, 0, input_blinding_key[0], output_blinding_key) == 0);
+    CHECK(ecount == 13);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 1, input_blinding_key[0], output_blinding_key) != 0);
+    CHECK(ecount == 13);  /* the above line "succeeds" but generates an invalid proof as the input_index is wrong. it is fairly expensive to detect this. should we? */
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, n_inputs + 1, input_blinding_key[0], output_blinding_key) != 0);
+    CHECK(ecount == 13);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, NULL, output_blinding_key) == 0);
+    CHECK(ecount == 14);
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], NULL) == 0);
+    CHECK(ecount == 15);
+
+    CHECK(secp256k1_surjectionproof_generate(both, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag, 0, input_blinding_key[0], output_blinding_key) != 0);
+    /* check verify */
+    CHECK(secp256k1_surjectionproof_verify(none, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 16);
+    CHECK(secp256k1_surjectionproof_verify(sign, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 17);
+    CHECK(secp256k1_surjectionproof_verify(vrfy, &proof, ephemeral_input_tags, n_inputs, &ephemeral_output_tag) != 0);
+    CHECK(ecount == 17);
+
+    CHECK(secp256k1_surjectionproof_verify(vrfy, NULL, ephemeral_input_tags, n_inputs, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 18);
+    CHECK(secp256k1_surjectionproof_verify(vrfy, &proof, NULL, n_inputs, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 19);
+    CHECK(secp256k1_surjectionproof_verify(vrfy, &proof, ephemeral_input_tags, n_inputs - 1, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 19);
+    CHECK(secp256k1_surjectionproof_verify(vrfy, &proof, ephemeral_input_tags, n_inputs + 1, &ephemeral_output_tag) == 0);
+    CHECK(ecount == 19);
+    CHECK(secp256k1_surjectionproof_verify(vrfy, &proof, ephemeral_input_tags, n_inputs, NULL) == 0);
+    CHECK(ecount == 20);
+
+    /* Check serialize */
+    serialized_len = sizeof(serialized_proof);
+    CHECK(secp256k1_surjectionproof_serialize(none, serialized_proof, &serialized_len, &proof) != 0);
+    CHECK(ecount == 20);
+    serialized_len = sizeof(serialized_proof);
+    CHECK(secp256k1_surjectionproof_serialize(none, NULL, &serialized_len, &proof) == 0);
+    CHECK(ecount == 21);
+    serialized_len = sizeof(serialized_proof);
+    CHECK(secp256k1_surjectionproof_serialize(none, serialized_proof, NULL, &proof) == 0);
+    CHECK(ecount == 22);
+    serialized_len = sizeof(serialized_proof);
+    CHECK(secp256k1_surjectionproof_serialize(none, serialized_proof, &serialized_len, NULL) == 0);
+    CHECK(ecount == 23);
+
+    serialized_len = sizeof(serialized_proof);
+    CHECK(secp256k1_surjectionproof_serialize(none, serialized_proof, &serialized_len, &proof) != 0);
+    /* Check parse */
+    CHECK(secp256k1_surjectionproof_parse(none, &proof, serialized_proof, serialized_len) != 0);
+    CHECK(ecount == 23);
+    CHECK(secp256k1_surjectionproof_parse(none, NULL, serialized_proof, serialized_len) == 0);
+    CHECK(ecount == 24);
+    CHECK(secp256k1_surjectionproof_parse(none, &proof, NULL, serialized_len) == 0);
+    CHECK(ecount == 25);
+    CHECK(secp256k1_surjectionproof_parse(none, &proof, serialized_proof, 0) == 0);
+    CHECK(ecount == 25);
+
+    secp256k1_context_destroy(none);
+    secp256k1_context_destroy(sign);
+    secp256k1_context_destroy(vrfy);
+    secp256k1_context_destroy(both);
+}
+
+static void test_input_selection(size_t n_inputs) {
+    unsigned char seed[32];
+    size_t i;
+    size_t result;
+    size_t input_index;
+    size_t try_count = n_inputs * 100;
+    secp256k1_surjectionproof proof;
+    secp256k1_fixed_asset_tag fixed_input_tags[1000];
+    const size_t max_n_inputs = sizeof(fixed_input_tags) / sizeof(fixed_input_tags[0]) - 1;
+
+    CHECK(n_inputs < max_n_inputs);
+    secp256k1_rand256(seed);
+
+    for (i = 0; i < n_inputs + 1; i++) {
+        secp256k1_rand256(fixed_input_tags[i].data);
+    }
+
+    /* cannot match output when told to use zero keys */
+    result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, 0, &fixed_input_tags[0], try_count, seed);
+    CHECK(result == 0);
+    CHECK(secp256k1_surjectionproof_n_used_inputs(ctx, &proof) == 0);
+    CHECK(secp256k1_surjectionproof_n_total_inputs(ctx, &proof) == n_inputs);
+    CHECK(secp256k1_surjectionproof_serialized_size(ctx, &proof) == 34 + (n_inputs + 7) / 8);
+    if (n_inputs > 0) {
+        /* succeed in 100*n_inputs tries (probability of failure e^-100) */
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, 1, &fixed_input_tags[0], try_count, seed);
+        CHECK(result > 0);
+        CHECK(result < n_inputs * 10);
+        CHECK(secp256k1_surjectionproof_n_used_inputs(ctx, &proof) == 1);
+        CHECK(secp256k1_surjectionproof_n_total_inputs(ctx, &proof) == n_inputs);
+        CHECK(secp256k1_surjectionproof_serialized_size(ctx, &proof) == 66 + (n_inputs + 7) / 8);
+        CHECK(input_index == 0);
+    }
+
+    if (n_inputs >= 3) {
+        /* succeed in 10*n_inputs tries (probability of failure e^-10) */
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[1], try_count, seed);
+        CHECK(result > 0);
+        CHECK(secp256k1_surjectionproof_n_used_inputs(ctx, &proof) == 3);
+        CHECK(secp256k1_surjectionproof_n_total_inputs(ctx, &proof) == n_inputs);
+        CHECK(secp256k1_surjectionproof_serialized_size(ctx, &proof) == 130 + (n_inputs + 7) / 8);
+        CHECK(input_index == 1);
+
+        /* fail, key not found */
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, 3, &fixed_input_tags[n_inputs], try_count, seed);
+        CHECK(result == 0);
+
+        /* succeed on first try when told to use all keys */
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, n_inputs, &fixed_input_tags[0], try_count, seed);
+        CHECK(result == 1);
+        CHECK(secp256k1_surjectionproof_n_used_inputs(ctx, &proof) == n_inputs);
+        CHECK(secp256k1_surjectionproof_n_total_inputs(ctx, &proof) == n_inputs);
+        CHECK(secp256k1_surjectionproof_serialized_size(ctx, &proof) == 2 + 32 * (n_inputs + 1) + (n_inputs + 7) / 8);
+        CHECK(input_index == 0);
+
+        /* succeed in less than 64 tries when told to use half keys. (probability of failure 2^-64) */
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, n_inputs / 2, &fixed_input_tags[0], 64, seed);
+        CHECK(result > 0);
+        CHECK(result < 64);
+        CHECK(secp256k1_surjectionproof_n_used_inputs(ctx, &proof) == n_inputs / 2);
+        CHECK(secp256k1_surjectionproof_n_total_inputs(ctx, &proof) == n_inputs);
+        CHECK(secp256k1_surjectionproof_serialized_size(ctx, &proof) == 2 + 32 * (n_inputs / 2 + 1) + (n_inputs + 7) / 8);
+        CHECK(input_index == 0);
+    }
+}
+
+/** Runs surjectionproof_initilize multiple times and records the number of times each input was used.
+ */
+static void test_input_selection_distribution_helper(const secp256k1_fixed_asset_tag* fixed_input_tags, const size_t n_input_tags, const size_t n_input_tags_to_use, size_t *used_inputs) {
+    secp256k1_surjectionproof proof;
+    size_t input_index;
+    size_t i;
+    size_t j;
+    unsigned char seed[32];
+    size_t result;
+    for (i = 0; i < n_input_tags; i++) {
+        used_inputs[i] = 0;
+    }
+    for(j = 0; j < 10000; j++) {
+        secp256k1_rand256(seed);
+        result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_input_tags, n_input_tags_to_use, &fixed_input_tags[0], 64, seed);
+        CHECK(result > 0);
+
+        for (i = 0; i < n_input_tags; i++) {
+            if (proof.used_inputs[i / 8] & (1 << (i % 8))) {
+                used_inputs[i] += 1;
+            }
+        }
+    }
+}
+
+/** Probabilistic test of the distribution of used_inputs after surjectionproof_initialize.
+ * Each confidence interval assertion fails incorrectly with a probability of 2^-128.
+ */
+static void test_input_selection_distribution(void) {
+    size_t i;
+    size_t n_input_tags_to_use;
+    const size_t n_inputs = 4;
+    secp256k1_fixed_asset_tag fixed_input_tags[4];
+    size_t used_inputs[4];
+
+    for (i = 0; i < n_inputs; i++) {
+        secp256k1_rand256(fixed_input_tags[i].data);
+    }
+
+    /* If there is one input tag to use, initialize must choose the one equal to fixed_output_tag. */
+    n_input_tags_to_use = 1;
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] == 10000);
+    CHECK(used_inputs[1] == 0);
+    CHECK(used_inputs[2] == 0);
+    CHECK(used_inputs[3] == 0);
+
+    n_input_tags_to_use = 2;
+    /* The input equal to the fixed_output_tag must be included in all used_inputs sets.
+     * For each fixed_input_tag != fixed_output_tag the probability that it's included
+     * in the used_inputs set is P(used_input|not fixed_output_tag) = 1/3.
+     */
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] == 10000);
+    CHECK(used_inputs[1] > 2725 && used_inputs[1] < 3961);
+    CHECK(used_inputs[2] > 2725 && used_inputs[2] < 3961);
+    CHECK(used_inputs[3] > 2725 && used_inputs[3] < 3961);
+
+    n_input_tags_to_use = 3;
+    /* P(used_input|not fixed_output_tag) = 2/3 */
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] == 10000);
+    CHECK(used_inputs[1] > 6039 && used_inputs[1] < 7275);
+    CHECK(used_inputs[2] > 6039 && used_inputs[2] < 7275);
+    CHECK(used_inputs[3] > 6039 && used_inputs[3] < 7275);
+
+
+    n_input_tags_to_use = 1;
+    /* Create second input tag that is equal to the output tag. Therefore, when using only
+     * one input we have P(used_input|fixed_output_tag) = 1/2 and P(used_input|not fixed_output_tag) = 0
+     */
+    memcpy(fixed_input_tags[0].data, fixed_input_tags[1].data, 32);
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] > 4345 && used_inputs[0] < 5655);
+    CHECK(used_inputs[1] > 4345 && used_inputs[1] < 5655);
+    CHECK(used_inputs[2] == 0);
+    CHECK(used_inputs[3] == 0);
+
+    n_input_tags_to_use = 2;
+    /* When choosing 2 inputs in initialization there are 5 possible combinations of
+     * input indexes {(0, 1), (1, 2), (0, 3), (1, 3), (0, 2)}. Therefore we have
+     * P(used_input|fixed_output_tag) = 3/5 and P(used_input|not fixed_output_tag) = 2/5.
+     */
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] > 5352 && used_inputs[0] < 6637);
+    CHECK(used_inputs[1] > 5352 && used_inputs[1] < 6637);
+    CHECK(used_inputs[2] > 3363 && used_inputs[2] < 4648);
+    CHECK(used_inputs[3] > 3363 && used_inputs[3] < 4648);
+
+    n_input_tags_to_use = 3;
+    /* There are 4 combinations, each with all inputs except one. Therefore we have
+     * P(used_input|fixed_output_tag) = 3/4 and P(used_input|not fixed_output_tag) = 3/4.
+     */
+    test_input_selection_distribution_helper(fixed_input_tags, n_inputs, n_input_tags_to_use, used_inputs);
+    CHECK(used_inputs[0] > 6918 && used_inputs[0] < 8053);
+    CHECK(used_inputs[1] > 6918 && used_inputs[1] < 8053);
+    CHECK(used_inputs[2] > 6918 && used_inputs[2] < 8053);
+    CHECK(used_inputs[3] > 6918 && used_inputs[3] < 8053);
+}
+
+static void test_gen_verify(size_t n_inputs, size_t n_used) {
+    unsigned char seed[32];
+    secp256k1_surjectionproof proof;
+    unsigned char serialized_proof[SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX];
+    unsigned char serialized_proof_trailing[SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX + 1];
+    size_t serialized_len = SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX;
+    secp256k1_fixed_asset_tag fixed_input_tags[1000];
+    secp256k1_generator ephemeral_input_tags[1000];
+    unsigned char *input_blinding_key[1000];
+    const size_t max_n_inputs = sizeof(fixed_input_tags) / sizeof(fixed_input_tags[0]) - 1;
+    size_t try_count = n_inputs * 100;
+    size_t key_index;
+    size_t input_index;
+    size_t i;
+    int result;
+
+    /* setup */
+    CHECK(n_used <= n_inputs);
+    CHECK(n_inputs < max_n_inputs);
+    secp256k1_rand256(seed);
+
+    key_index = (((size_t) seed[0] << 8) + seed[1]) % n_inputs;
+
+    for (i = 0; i < n_inputs + 1; i++) {
+        input_blinding_key[i] = malloc(32);
+        secp256k1_rand256(input_blinding_key[i]);
+        /* choose random fixed tag, except that for the output one copy from the key_index */
+        if (i < n_inputs) {
+            secp256k1_rand256(fixed_input_tags[i].data);
+        } else {
+            memcpy(&fixed_input_tags[i], &fixed_input_tags[key_index], sizeof(fixed_input_tags[i]));
+        }
+        CHECK(secp256k1_generator_generate_blinded(ctx, &ephemeral_input_tags[i], fixed_input_tags[i].data, input_blinding_key[i]));
+    }
+
+    /* test */
+    result = secp256k1_surjectionproof_initialize(ctx, &proof, &input_index, fixed_input_tags, n_inputs, n_used, &fixed_input_tags[key_index], try_count, seed);
+    if (n_used == 0) {
+        CHECK(result == 0);
+        return;
+    }
+    CHECK(result > 0);
+    CHECK(input_index == key_index);
+
+    result = secp256k1_surjectionproof_generate(ctx, &proof, ephemeral_input_tags, n_inputs, &ephemeral_input_tags[n_inputs], input_index, input_blinding_key[input_index], input_blinding_key[n_inputs]);
+    CHECK(result == 1);
+
+    CHECK(secp256k1_surjectionproof_serialize(ctx, serialized_proof, &serialized_len, &proof));
+    CHECK(serialized_len == secp256k1_surjectionproof_serialized_size(ctx, &proof));
+    CHECK(serialized_len == SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES(n_inputs, n_used));
+
+    /* trailing garbage */
+    memcpy(&serialized_proof_trailing, &serialized_proof, serialized_len);
+    serialized_proof_trailing[serialized_len] = seed[0];
+    CHECK(secp256k1_surjectionproof_parse(ctx, &proof, serialized_proof, serialized_len + 1) == 0);
+
+    CHECK(secp256k1_surjectionproof_parse(ctx, &proof, serialized_proof, serialized_len));
+    result = secp256k1_surjectionproof_verify(ctx, &proof, ephemeral_input_tags, n_inputs, &ephemeral_input_tags[n_inputs]);
+    CHECK(result == 1);
+    /* various fail cases */
+    if (n_inputs > 1) {
+        result = secp256k1_surjectionproof_verify(ctx, &proof, ephemeral_input_tags, n_inputs, &ephemeral_input_tags[n_inputs - 1]);
+        CHECK(result == 0);
+
+        /* number of entries in ephemeral_input_tags array is less than proof.n_inputs */
+        n_inputs -= 1;
+        result = secp256k1_surjectionproof_generate(ctx, &proof, ephemeral_input_tags, n_inputs, &ephemeral_input_tags[n_inputs], input_index, input_blinding_key[input_index], input_blinding_key[n_inputs]);
+        CHECK(result == 0);
+        result = secp256k1_surjectionproof_verify(ctx, &proof, ephemeral_input_tags, n_inputs, &ephemeral_input_tags[n_inputs - 1]);
+        CHECK(result == 0);
+        n_inputs += 1;
+    }
+
+    /* cleanup */
+    for (i = 0; i < n_inputs + 1; i++) {
+        free(input_blinding_key[i]);
+    }
+}
+
+/* check that a proof with empty n_used_inputs is invalid */
+static void test_no_used_inputs_verify(void) {
+    secp256k1_surjectionproof proof;
+    secp256k1_fixed_asset_tag fixed_input_tag;
+    secp256k1_fixed_asset_tag fixed_output_tag;
+    secp256k1_generator ephemeral_input_tags[1];
+    size_t n_ephemeral_input_tags = 1;
+    secp256k1_generator ephemeral_output_tag;
+    unsigned char blinding_key[32];
+    secp256k1_ge inputs[1];
+    secp256k1_ge output;
+    secp256k1_sha256 sha256_e0;
+    int result;
+
+    /* Create proof that doesn't use inputs. secp256k1_surjectionproof_initialize
+     * will not work here since it insists on selecting an input that matches the output. */
+    proof.n_inputs = 1;
+    memset(proof.used_inputs, 0, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS / 8);
+
+    /* create different fixed input and output tags */
+    secp256k1_rand256(fixed_input_tag.data);
+    secp256k1_rand256(fixed_output_tag.data);
+
+    /* blind fixed output tags with random blinding key */
+    secp256k1_rand256(blinding_key);
+    CHECK(secp256k1_generator_generate_blinded(ctx, &ephemeral_input_tags[0], fixed_input_tag.data, blinding_key));
+    CHECK(secp256k1_generator_generate_blinded(ctx, &ephemeral_output_tag, fixed_output_tag.data, blinding_key));
+
+    /* create "borromean signature" which is just a hash of metadata (pubkeys, etc) in this case */
+    secp256k1_generator_load(&output, &ephemeral_output_tag);
+    secp256k1_generator_load(&inputs[0], &ephemeral_input_tags[0]);
+    secp256k1_surjection_genmessage(proof.data, inputs, 1, &output);
+    secp256k1_sha256_initialize(&sha256_e0);
+    secp256k1_sha256_write(&sha256_e0, proof.data, 32);
+    secp256k1_sha256_finalize(&sha256_e0, proof.data);
+
+    result = secp256k1_surjectionproof_verify(ctx, &proof, ephemeral_input_tags, n_ephemeral_input_tags, &ephemeral_output_tag);
+    CHECK(result == 0);
+}
+
+void test_bad_serialize(void) {
+    secp256k1_surjectionproof proof;
+    unsigned char serialized_proof[SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX];
+    size_t serialized_len;
+
+    proof.n_inputs = 0;
+    serialized_len = 2 + 31;
+    /* e0 is one byte too short */
+    CHECK(secp256k1_surjectionproof_serialize(ctx, serialized_proof, &serialized_len, &proof) == 0);
+}
+
+void test_bad_parse(void) {
+    secp256k1_surjectionproof proof;
+    unsigned char serialized_proof0[] = { 0x00 };
+    unsigned char serialized_proof1[] = { 0x01, 0x00 };
+    unsigned char serialized_proof2[33] = { 0 };
+
+    /* Missing total input count */
+    CHECK(secp256k1_surjectionproof_parse(ctx, &proof, serialized_proof0, sizeof(serialized_proof0)) == 0);
+    /* Missing bitmap */
+    CHECK(secp256k1_surjectionproof_parse(ctx, &proof, serialized_proof1, sizeof(serialized_proof1)) == 0);
+    /* Missing e0 value */
+    CHECK(secp256k1_surjectionproof_parse(ctx, &proof, serialized_proof2, sizeof(serialized_proof2)) == 0);
+}
+
+void run_surjection_tests(void) {
+    int i;
+    for (i = 0; i < count; i++) {
+        test_surjectionproof_api();
+    }
+
+    test_input_selection(0);
+    test_input_selection(1);
+    test_input_selection(5);
+    test_input_selection(100);
+    test_input_selection(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS);
+
+    test_input_selection_distribution();
+    test_gen_verify(10, 3);
+    test_gen_verify(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS);
+    test_no_used_inputs_verify();
+    test_bad_serialize();
+    test_bad_parse();
+}
+
+#endif

src/modules/whitelist/Makefile.am.include

@@ -0,0 +1,10 @@
+include_HEADERS += include/secp256k1_whitelist.h
+noinst_HEADERS += src/modules/whitelist/whitelist_impl.h
+noinst_HEADERS += src/modules/whitelist/main_impl.h
+noinst_HEADERS += src/modules/whitelist/tests_impl.h
+if USE_BENCHMARK
+noinst_PROGRAMS += bench_whitelist
+bench_whitelist_SOURCES = src/bench_whitelist.c
+bench_whitelist_LDADD = libsecp256k1.la $(SECP_LIBS)
+bench_generator_LDFLAGS = -static
+endif

src/modules/whitelist/main_impl.h

@@ -0,0 +1,174 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_WHITELIST_MAIN
+#define SECP256K1_MODULE_WHITELIST_MAIN
+
+#include "include/secp256k1_whitelist.h"
+#include "modules/whitelist/whitelist_impl.h"
+
+#define MAX_KEYS SECP256K1_WHITELIST_MAX_N_KEYS  /* shorter alias */
+
+int secp256k1_whitelist_sign(const secp256k1_context* ctx, secp256k1_whitelist_signature *sig, const secp256k1_pubkey *online_pubkeys, const secp256k1_pubkey *offline_pubkeys, const size_t n_keys, const secp256k1_pubkey *sub_pubkey, const unsigned char *online_seckey, const unsigned char *summed_seckey, const size_t index, secp256k1_nonce_function noncefp, const void *noncedata) {
+    secp256k1_gej pubs[MAX_KEYS];
+    secp256k1_scalar s[MAX_KEYS];
+    secp256k1_scalar sec, non;
+    unsigned char msg32[32];
+    int ret;
+
+    if (noncefp == NULL) {
+        noncefp = secp256k1_nonce_function_default;
+    }
+
+    /* Sanity checks */
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(online_pubkeys != NULL);
+    ARG_CHECK(offline_pubkeys != NULL);
+    ARG_CHECK(n_keys <= MAX_KEYS);
+    ARG_CHECK(sub_pubkey != NULL);
+    ARG_CHECK(online_seckey != NULL);
+    ARG_CHECK(summed_seckey != NULL);
+    ARG_CHECK(index < n_keys);
+
+    /* Compute pubkeys: online_pubkey + tweaked(offline_pubkey + address), and message */
+    ret = secp256k1_whitelist_compute_keys_and_message(ctx, msg32, pubs, online_pubkeys, offline_pubkeys, n_keys, sub_pubkey);
+
+    /* Compute signing key: online_seckey + tweaked(summed_seckey) */
+    if (ret) {
+        ret = secp256k1_whitelist_compute_tweaked_privkey(ctx, &sec, online_seckey, summed_seckey);
+    }
+    /* Compute nonce and random s-values */
+    if (ret) {
+        unsigned char seckey32[32];
+        unsigned int count = 0;
+        int overflow = 0;
+
+        secp256k1_scalar_get_b32(seckey32, &sec);
+        while (1) {
+            size_t i;
+            unsigned char nonce32[32];
+            int done;
+            ret = noncefp(nonce32, msg32, seckey32, NULL, (void*)noncedata, count);
+            if (!ret) {
+                break;
+            }
+            secp256k1_scalar_set_b32(&non, nonce32, &overflow);
+            memset(nonce32, 0, 32);
+            if (overflow || secp256k1_scalar_is_zero(&non)) {
+                count++;
+                continue;
+            }
+            done = 1;
+            for (i = 0; i < n_keys; i++) {
+                msg32[0] ^= i + 1;
+                msg32[1] ^= (i + 1) / 0x100;
+                ret = noncefp(&sig->data[32 * (i + 1)], msg32, seckey32, NULL, (void*)noncedata, count);
+                if (!ret) {
+                    break;
+                }
+                secp256k1_scalar_set_b32(&s[i], &sig->data[32 * (i + 1)], &overflow);
+                msg32[0] ^= i + 1;
+                msg32[1] ^= (i + 1) / 0x100;
+                if (overflow || secp256k1_scalar_is_zero(&s[i])) {
+                    count++;
+                    done = 0;
+                    break;
+                }
+            }
+            if (done) {
+                break;
+            }
+        }
+        memset(seckey32, 0, 32);
+    }
+    /* Actually sign */
+    if (ret) {
+        sig->n_keys = n_keys;
+        ret = secp256k1_borromean_sign(&ctx->ecmult_ctx, &ctx->ecmult_gen_ctx, &sig->data[0], s, pubs, &non, &sec, &n_keys, &index, 1, msg32, 32);
+        /* Signing will change s[index], so update in the sig structure */
+        secp256k1_scalar_get_b32(&sig->data[32 * (index + 1)], &s[index]);
+    }
+
+    secp256k1_scalar_clear(&non);
+    secp256k1_scalar_clear(&sec);
+    return ret;
+}
+
+int secp256k1_whitelist_verify(const secp256k1_context* ctx, const secp256k1_whitelist_signature *sig, const secp256k1_pubkey *online_pubkeys, const secp256k1_pubkey *offline_pubkeys, const size_t n_keys, const secp256k1_pubkey *sub_pubkey) {
+    secp256k1_scalar s[MAX_KEYS];
+    secp256k1_gej pubs[MAX_KEYS];
+    unsigned char msg32[32];
+    size_t i;
+
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(secp256k1_ecmult_context_is_built(&ctx->ecmult_ctx));
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(online_pubkeys != NULL);
+    ARG_CHECK(offline_pubkeys != NULL);
+    ARG_CHECK(sub_pubkey != NULL);
+
+    if (sig->n_keys > MAX_KEYS || sig->n_keys != n_keys) {
+        return 0;
+    }
+    for (i = 0; i < sig->n_keys; i++) {
+        int overflow = 0;
+        secp256k1_scalar_set_b32(&s[i], &sig->data[32 * (i + 1)], &overflow);
+        if (overflow || secp256k1_scalar_is_zero(&s[i])) {
+            return 0;
+        }
+    }
+
+    /* Compute pubkeys: online_pubkey + tweaked(offline_pubkey + address), and message */
+    if (!secp256k1_whitelist_compute_keys_and_message(ctx, msg32, pubs, online_pubkeys, offline_pubkeys, sig->n_keys, sub_pubkey)) {
+        return 0;
+    }
+    /* Do verification */
+    return secp256k1_borromean_verify(&ctx->ecmult_ctx, NULL, &sig->data[0], s, pubs, &sig->n_keys, 1, msg32, 32);
+}
+
+size_t secp256k1_whitelist_signature_n_keys(const secp256k1_whitelist_signature *sig) {
+    return sig->n_keys;
+}
+
+int secp256k1_whitelist_signature_parse(const secp256k1_context* ctx, secp256k1_whitelist_signature *sig, const unsigned char *input, size_t input_len) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(sig != NULL);
+    ARG_CHECK(input != NULL);
+
+    if (input_len == 0) {
+        return 0;
+    }
+
+    sig->n_keys = input[0];
+    if (sig->n_keys >= MAX_KEYS || input_len != 1 + 32 * (sig->n_keys + 1)) {
+        return 0;
+    }
+    memcpy(&sig->data[0], &input[1], 32 * (sig->n_keys + 1));
+
+    return 1;
+}
+
+int secp256k1_whitelist_signature_serialize(const secp256k1_context* ctx, unsigned char *output, size_t *output_len, const secp256k1_whitelist_signature *sig) {
+    VERIFY_CHECK(ctx != NULL);
+    ARG_CHECK(output != NULL);
+    ARG_CHECK(output_len != NULL);
+    ARG_CHECK(sig != NULL);
+
+    if (*output_len < 1 + 32 * (sig->n_keys + 1)) {
+        return 0;
+    }
+
+    output[0] = sig->n_keys;
+    memcpy(&output[1], &sig->data[0], 32 * (sig->n_keys + 1));
+    *output_len = 1 + 32 * (sig->n_keys + 1);
+
+    return 1;
+}
+
+#endif

src/modules/whitelist/tests_impl.h

@@ -0,0 +1,151 @@
+/**********************************************************************
+ * Copyright (c) 2014-2016 Pieter Wuille, Andrew Poelstra             *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_MODULE_WHITELIST_TESTS
+#define SECP256K1_MODULE_WHITELIST_TESTS
+
+#include "include/secp256k1_whitelist.h"
+
+void test_whitelist_end_to_end(const size_t n_keys) {
+    unsigned char **online_seckey = (unsigned char **) malloc(n_keys * sizeof(*online_seckey));
+    unsigned char **summed_seckey = (unsigned char **) malloc(n_keys * sizeof(*summed_seckey));
+    secp256k1_pubkey *online_pubkeys = (secp256k1_pubkey *) malloc(n_keys * sizeof(*online_pubkeys));
+    secp256k1_pubkey *offline_pubkeys = (secp256k1_pubkey *) malloc(n_keys * sizeof(*offline_pubkeys));
+
+    secp256k1_scalar ssub;
+    unsigned char csub[32];
+    secp256k1_pubkey sub_pubkey;
+
+    /* Generate random keys */
+    size_t i;
+    /* Start with subkey */
+    random_scalar_order_test(&ssub);
+    secp256k1_scalar_get_b32(csub, &ssub);
+    CHECK(secp256k1_ec_seckey_verify(ctx, csub) == 1);
+    CHECK(secp256k1_ec_pubkey_create(ctx, &sub_pubkey, csub) == 1);
+    /* Then offline and online whitelist keys */
+    for (i = 0; i < n_keys; i++) {
+        secp256k1_scalar son, soff;
+
+        online_seckey[i] = (unsigned char *) malloc(32);
+        summed_seckey[i] = (unsigned char *) malloc(32);
+
+        /* Create two keys */
+        random_scalar_order_test(&son);
+        secp256k1_scalar_get_b32(online_seckey[i], &son);
+        CHECK(secp256k1_ec_seckey_verify(ctx, online_seckey[i]) == 1);
+        CHECK(secp256k1_ec_pubkey_create(ctx, &online_pubkeys[i], online_seckey[i]) == 1);
+
+        random_scalar_order_test(&soff);
+        secp256k1_scalar_get_b32(summed_seckey[i], &soff);
+        CHECK(secp256k1_ec_seckey_verify(ctx, summed_seckey[i]) == 1);
+        CHECK(secp256k1_ec_pubkey_create(ctx, &offline_pubkeys[i], summed_seckey[i]) == 1);
+
+        /* Make summed_seckey correspond to the sum of offline_pubkey and sub_pubkey */
+        secp256k1_scalar_add(&soff, &soff, &ssub);
+        secp256k1_scalar_get_b32(summed_seckey[i], &soff);
+        CHECK(secp256k1_ec_seckey_verify(ctx, summed_seckey[i]) == 1);
+    }
+
+    /* Sign/verify with each one */
+    for (i = 0; i < n_keys; i++) {
+        unsigned char serialized[32 + 4 + 32 * SECP256K1_WHITELIST_MAX_N_KEYS] = {0};
+        size_t slen = sizeof(serialized);
+        secp256k1_whitelist_signature sig;
+        secp256k1_whitelist_signature sig1;
+
+        CHECK(secp256k1_whitelist_sign(ctx, &sig, online_pubkeys, offline_pubkeys, n_keys, &sub_pubkey, online_seckey[i], summed_seckey[i], i, NULL, NULL));
+        CHECK(secp256k1_whitelist_verify(ctx, &sig, online_pubkeys, offline_pubkeys, n_keys, &sub_pubkey) == 1);
+        /* Check that exchanging keys causes a failure */
+        CHECK(secp256k1_whitelist_verify(ctx, &sig, offline_pubkeys, online_pubkeys, n_keys, &sub_pubkey) != 1);
+        /* Serialization round trip */
+        CHECK(secp256k1_whitelist_signature_serialize(ctx, serialized, &slen, &sig) == 1);
+        CHECK(slen == 33 + 32 * n_keys);
+        CHECK(secp256k1_whitelist_signature_parse(ctx, &sig1, serialized, slen) == 1);
+        /* (Check various bad-length conditions) */
+        CHECK(secp256k1_whitelist_signature_parse(ctx, &sig1, serialized, slen + 32) == 0);
+        CHECK(secp256k1_whitelist_signature_parse(ctx, &sig1, serialized, slen + 1) == 0);
+        CHECK(secp256k1_whitelist_signature_parse(ctx, &sig1, serialized, slen - 1) == 0);
+        CHECK(secp256k1_whitelist_signature_parse(ctx, &sig1, serialized, 0) == 0);
+        CHECK(secp256k1_whitelist_verify(ctx, &sig1, online_pubkeys, offline_pubkeys, n_keys, &sub_pubkey) == 1);
+        CHECK(secp256k1_whitelist_verify(ctx, &sig1, offline_pubkeys, online_pubkeys, n_keys, &sub_pubkey) != 1);
+
+        /* Test n_keys */
+        CHECK(secp256k1_whitelist_signature_n_keys(&sig) == n_keys);
+        CHECK(secp256k1_whitelist_signature_n_keys(&sig1) == n_keys);
+
+        /* Test bad number of keys in signature */
+        sig.n_keys = n_keys + 1;
+        CHECK(secp256k1_whitelist_verify(ctx, &sig, offline_pubkeys, online_pubkeys, n_keys, &sub_pubkey) != 1);
+        sig.n_keys = n_keys;
+    }
+
+    for (i = 0; i < n_keys; i++) {
+        free(online_seckey[i]);
+        free(summed_seckey[i]);
+    }
+    free(online_seckey);
+    free(summed_seckey);
+    free(online_pubkeys);
+    free(offline_pubkeys);
+}
+
+void test_whitelist_bad_parse(void) {
+    secp256k1_whitelist_signature sig;
+
+    const unsigned char serialized0[] = { 1+32*(0+1) };
+    const unsigned char serialized1[] = {
+        0x00,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06
+    };
+    const unsigned char serialized2[] = {
+        0x01,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07
+    };
+
+    /* Empty input */
+    CHECK(secp256k1_whitelist_signature_parse(ctx, &sig, serialized0, 0) == 0);
+    /* Misses one byte of e0 */
+    CHECK(secp256k1_whitelist_signature_parse(ctx, &sig, serialized1, sizeof(serialized1)) == 0);
+    /* Enough bytes for e0, but there is no s value */
+    CHECK(secp256k1_whitelist_signature_parse(ctx, &sig, serialized2, sizeof(serialized2)) == 0);
+}
+
+void test_whitelist_bad_serialize(void) {
+    unsigned char serialized[] = {
+        0x00,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07
+    };
+    size_t serialized_len;
+    secp256k1_whitelist_signature sig;
+
+    CHECK(secp256k1_whitelist_signature_parse(ctx, &sig, serialized, sizeof(serialized)) == 1);
+    serialized_len = sizeof(serialized) - 1;
+    /* Output buffer is one byte too short */
+    CHECK(secp256k1_whitelist_signature_serialize(ctx, serialized, &serialized_len, &sig) == 0);
+}
+
+void run_whitelist_tests(void) {
+    int i;
+    test_whitelist_bad_parse();
+    test_whitelist_bad_serialize();
+    for (i = 0; i < count; i++) {
+        test_whitelist_end_to_end(1);
+        test_whitelist_end_to_end(10);
+        test_whitelist_end_to_end(50);
+    }
+}
+
+#endif

src/modules/whitelist/whitelist.md

@@ -0,0 +1,107 @@
+Address Whitelisting Module
+===========================
+
+This module implements a scheme by which members of some group, having fixed
+signing keys, can prove control of an arbitrary other key without associating
+their own identity (only that they belong to the group) to the new key. The
+application is to patch ring-signature-like behaviour onto systems such as
+Bitcoin or PGP which do not directly support this.
+
+We refer to such delegation as "whitelisting" because we expect it to be used
+to build a dynamic whitelist of authorized keys.
+
+For example, imagine a private sidechain with a fixed membership set but
+stronger privacy properties than Bitcoin. When moving coins from this system
+to Bitcoin, it is desirable that the destination Bitcoin addresses be provably
+in control of some user of the sidechain. This prevents malicious or erroneous
+behaviour on the sidechain, which can likely be resolved by its participants,
+from translating to theft on the wider Bitcoin network, which is irreversible.
+
+### Unused Schemes and Design Rationale
+
+#### Direct Signing
+
+An obvious scheme for such delegation is to simply have participants sign the
+key they want to whitelist. To avoid revealing their specific identity, they
+could use a ring signature. The problem with this is that it really only proves
+that a participant *signed off* on a key, not that they control it. Thus any
+security failure that allows text substitution could be used to subvert this
+and redirect coins to an attacker-controlled address.
+
+#### Signing with Difference-of-Keys
+
+A less obvious scheme is to have a participant sign an arbitrary message with
+the sum of her key `P` and the whitelisted key `W`. Such a signature with the key
+`P + W` proves knowledge of either (a) discrete logarithms of both `P` and `W`;
+or (b) neither. This makes directly attacking participants' signing schemes much
+harder, but allows an attacker to whitelist arbitrary "cancellation" keys by
+computing `W` as the difference between an attacker-controlled key and `P`.
+Because to spend the funds the attacker must produce a signature with `W`, the
+coins will be unspendable until attacker and the legitimate participant owning
+`P` cooperate.
+
+In an important sense, this "cancellation" attack is a good thing: it enables
+*offline delegation*. That is, the key `P` does not need to be available at the
+time of delegation. Instead, participants could choose `S = P + W`, sign with
+this to delegate, and only later compute the discrete logarithm of `W = P - S`.
+This allows `P` to be in cold storage or be otherwise inaccessible, improving
+the overall system security.
+
+#### Signing with Tweaked-Difference-of-Keys
+
+A modification of this scheme, which prevents this "cancellation" attack, is to
+instead have participants sign some message with the key `P + H(W)W`, for `H`
+some random-oracle hash that maps group elements to scalars. This key, and its
+discrete logarithm, cannot be known until after `W` is chosen, so `W` cannot
+be selected as the difference between it and `P`. (Note that `P` could still
+be some chosen difference; however `P` is a fixed key and must be verified
+out-of-band to have come from a legitimate participant anyway.)
+
+This scheme is almost what we want, but it no longer supports offline
+delegation. However, we can get this back by introducing a new key, `P'`,
+and signing with the key `P + H(W + P')(W + P')`. This gives us the best
+of both worlds: `P'` does not need to be online to delegate, allowing it
+to be securely stored and preventing real-time attacks; `P` does need to
+be online, but its compromise only allows an attacker to whitelist keys he does
+not control alone.
+
+### Our Scheme
+
+Our scheme works as follows: each participant `i` chooses two keys, `P_i` and `Q_i`.
+We refer to `P_i` as the "online key" and `Q_i` as the "offline key". To whitelist
+a key `W`, the participant computes the key `L_j = P_j + H(W + Q_j)(W + Q_j)` for
+every participant `j`. Then she will know the discrete logarithm of `L_i` for her
+own `i`.
+
+Next, she signs a message containing every `P_i` and `Q_i` as well as `W` with
+a ring signature over all the keys `L_j`. This proves that she knows the discrete
+logarithm of some `L_i` (though it is zero-knowledge which one), and therefore
+knows:
+1. The discrete logarithms of all of `W`, `P_i` and `Q_i`; or
+2. The discrete logarithm of `P_i` but of *neither* `W` nor `Q_i`.
+In other words, compromise of the online key `P_i` allows an attacker to whitelist
+"cancellation keys" for which the attacker alone does not know the discrete logarithm;
+to whitelist an attacker-controlled key, he must compromise both `P_i` and `Q_i`. This is difficult
+because by design, only the sum `S = W + Q_i` is used when signing; then by choosing
+`S` freely, a participant can delegate without the secret key to `Q_i` ever being online.
+(Later, when she wants to actually use `W`, she will need to compute its key as the
+difference between `S` and `Q_i`; but this can be done offline and much later
+and with more expensive security requirements.)
+
+The message to be signed contains all public keys to prevent a class of attacks
+centered around choosing keys to match pre-computed signatures. In our proposed
+use case, whitelisted keys already must be computed before they are signed, and
+the remaining public keys are verified out-of-band when setting up the system,
+so there is no direct benefit to this. We do it only to reduce fragility and
+increase safety of unforeseen uses.
+
+Having to access the offline key `Q_i` to compute the secret to the sum `W +
+Q_i` for every authorization is onerous.  Instead, if the whitelisted keys are
+created using
+[BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki)
+unhardened derivation, the sum can be computed on an online machine. In order
+to achieve that, the offline key `Q_j` is set to the negated last hardened
+BIP32 derived parent key (typically, the public key corresponding to the xpub).
+As a result `W + Q_i = I_L*G` where `I_L` is the public tweak used
+to derive `W` and can be easily computed online using the extended public key
+and the derivation path.

src/modules/whitelist/whitelist_impl.h

@@ -0,0 +1,129 @@
+/**********************************************************************
+ * Copyright (c) 2016 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_WHITELIST_IMPL_H_
+#define _SECP256K1_WHITELIST_IMPL_H_
+
+static int secp256k1_whitelist_hash_pubkey(secp256k1_scalar* output, secp256k1_gej* pubkey) {
+    unsigned char h[32];
+    unsigned char c[33];
+    secp256k1_sha256 sha;
+    int overflow = 0;
+    size_t size = 33;
+    secp256k1_ge ge;
+
+    secp256k1_ge_set_gej(&ge, pubkey);
+
+    secp256k1_sha256_initialize(&sha);
+    if (!secp256k1_eckey_pubkey_serialize(&ge, c, &size, SECP256K1_EC_COMPRESSED)) {
+        return 0;
+    }
+    secp256k1_sha256_write(&sha, c, size);
+    secp256k1_sha256_finalize(&sha, h);
+
+    secp256k1_scalar_set_b32(output, h, &overflow);
+    if (overflow || secp256k1_scalar_is_zero(output)) {
+        /* This return path is mathematically impossible to hit */
+        secp256k1_scalar_clear(output);
+        return 0;
+    }
+    return 1;
+}
+
+static int secp256k1_whitelist_tweak_pubkey(const secp256k1_context* ctx, secp256k1_gej* pub_tweaked) {
+    secp256k1_scalar tweak;
+    secp256k1_scalar zero;
+    int ret;
+
+    secp256k1_scalar_set_int(&zero, 0);
+
+    ret = secp256k1_whitelist_hash_pubkey(&tweak, pub_tweaked);
+    if (ret) {
+        secp256k1_ecmult(&ctx->ecmult_ctx, pub_tweaked, pub_tweaked, &tweak, &zero);
+    }
+    return ret;
+}
+
+static int secp256k1_whitelist_compute_tweaked_privkey(const secp256k1_context* ctx, secp256k1_scalar* skey, const unsigned char *online_key, const unsigned char *summed_key) {
+    secp256k1_scalar tweak;
+    int ret = 1;
+    int overflow = 0;
+
+    secp256k1_scalar_set_b32(skey, summed_key, &overflow);
+    if (overflow || secp256k1_scalar_is_zero(skey)) {
+        ret = 0;
+    }
+    if (ret) {
+        secp256k1_gej pkeyj;
+        secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &pkeyj, skey);
+        ret = secp256k1_whitelist_hash_pubkey(&tweak, &pkeyj);
+    }
+    if (ret) {
+        secp256k1_scalar sonline;
+        secp256k1_scalar_mul(skey, skey, &tweak);
+
+        secp256k1_scalar_set_b32(&sonline, online_key, &overflow);
+        if (overflow || secp256k1_scalar_is_zero(&sonline)) {
+            ret = 0;
+        }
+        secp256k1_scalar_add(skey, skey, &sonline);
+        secp256k1_scalar_clear(&sonline);
+        secp256k1_scalar_clear(&tweak);
+    }
+
+    if (!ret) {
+        secp256k1_scalar_clear(skey);
+    }
+    return ret;
+}
+
+/* Takes a list of pubkeys and combines them to form the public keys needed
+ * for the ring signature; also produce a commitment to every one that will
+ * be our "message". */
+static int secp256k1_whitelist_compute_keys_and_message(const secp256k1_context* ctx, unsigned char *msg32, secp256k1_gej *keys, const secp256k1_pubkey *online_pubkeys, const secp256k1_pubkey *offline_pubkeys, const int n_keys, const secp256k1_pubkey *sub_pubkey) {
+    unsigned char c[33];
+    size_t size = 33;
+    secp256k1_sha256 sha;
+    int i;
+    secp256k1_ge subkey_ge;
+
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_pubkey_load(ctx, &subkey_ge, sub_pubkey);
+
+    /* commit to sub-key */
+    if (!secp256k1_eckey_pubkey_serialize(&subkey_ge, c, &size, SECP256K1_EC_COMPRESSED)) {
+        return 0;
+    }
+    secp256k1_sha256_write(&sha, c, size);
+    for (i = 0; i < n_keys; i++) {
+        secp256k1_ge offline_ge;
+        secp256k1_ge online_ge;
+        secp256k1_gej tweaked_gej;
+
+        /* commit to fixed keys */
+        secp256k1_pubkey_load(ctx, &offline_ge, &offline_pubkeys[i]);
+        if (!secp256k1_eckey_pubkey_serialize(&offline_ge, c, &size, SECP256K1_EC_COMPRESSED)) {
+            return 0;
+        }
+        secp256k1_sha256_write(&sha, c, size);
+        secp256k1_pubkey_load(ctx, &online_ge, &online_pubkeys[i]);
+        if (!secp256k1_eckey_pubkey_serialize(&online_ge, c, &size, SECP256K1_EC_COMPRESSED)) {
+            return 0;
+        }
+        secp256k1_sha256_write(&sha, c, size);
+
+        /* compute tweaked keys */
+        secp256k1_gej_set_ge(&tweaked_gej, &offline_ge);
+        secp256k1_gej_add_ge_var(&tweaked_gej, &tweaked_gej, &subkey_ge, NULL);
+        secp256k1_whitelist_tweak_pubkey(ctx, &tweaked_gej);
+        secp256k1_gej_add_ge_var(&keys[i], &tweaked_gej, &online_ge, NULL);
+    }
+    secp256k1_sha256_finalize(&sha, msg32);
+    return 1;
+}
+
+
+#endif

src/scalar.h

@@ -38,6 +38,9 @@ static void secp256k1_scalar_set_b32(secp256k1_scalar *r, const unsigned char *b
 /** Set a scalar to an unsigned integer. */
 static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsigned int v);
 
+/** Set a scalar to an unsigned 64-bit integer */
+static void secp256k1_scalar_set_u64(secp256k1_scalar *r, uint64_t v);
+
 /** Convert a scalar to a byte array. */
 static void secp256k1_scalar_get_b32(unsigned char *bin, const secp256k1_scalar* a);
 
@@ -103,4 +106,7 @@ static void secp256k1_scalar_split_lambda(secp256k1_scalar *r1, secp256k1_scalar
 /** Multiply a and b (without taking the modulus!), divide by 2**shift, and round to the nearest integer. Shift must be at least 256. */
 static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b, unsigned int shift);
 
+/** Generate two scalars from a 32-byte seed and an integer using the chacha20 stream cipher */
+static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx);
+
 #endif /* SECP256K1_SCALAR_H */

src/scalar_4x64_impl.h

@@ -7,6 +7,9 @@
 #ifndef SECP256K1_SCALAR_REPR_IMPL_H
 #define SECP256K1_SCALAR_REPR_IMPL_H
 
+#include "scalar.h"
+#include <string.h>
+
 /* Limbs of the secp256k1 order. */
 #define SECP256K1_N_0 ((uint64_t)0xBFD25E8CD0364141ULL)
 #define SECP256K1_N_1 ((uint64_t)0xBAAEDCE6AF48A03BULL)
@@ -38,6 +41,13 @@ SECP256K1_INLINE static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsig
     r->d[3] = 0;
 }
 
+SECP256K1_INLINE static void secp256k1_scalar_set_u64(secp256k1_scalar *r, uint64_t v) {
+    r->d[0] = v;
+    r->d[1] = 0;
+    r->d[2] = 0;
+    r->d[3] = 0;
+}
+
 SECP256K1_INLINE static unsigned int secp256k1_scalar_get_bits(const secp256k1_scalar *a, unsigned int offset, unsigned int count) {
     VERIFY_CHECK((offset + count - 1) >> 6 == offset >> 6);
     return (a->d[offset >> 6] >> (offset & 0x3F)) & ((((uint64_t)1) << count) - 1);
@@ -946,4 +956,94 @@ SECP256K1_INLINE static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r,
     secp256k1_scalar_cadd_bit(r, 0, (l[(shift - 1) >> 6] >> ((shift - 1) & 0x3f)) & 1);
 }
 
+#define ROTL32(x,n) ((x) << (n) | (x) >> (32-(n)))
+#define QUARTERROUND(a,b,c,d) \
+  a += b; d = ROTL32(d ^ a, 16); \
+  c += d; b = ROTL32(b ^ c, 12); \
+  a += b; d = ROTL32(d ^ a, 8); \
+  c += d; b = ROTL32(b ^ c, 7);
+
+#ifdef WORDS_BIGENDIAN
+#define LE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
+#define BE32(p) (p)
+#else
+#define BE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
+#define LE32(p) (p)
+#endif
+
+static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx) {
+    size_t n;
+    size_t over_count = 0;
+    uint32_t seed32[8];
+    uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+    int over1, over2;
+
+    memcpy((void *) seed32, (const void *) seed, 32);
+    do {
+        x0 = 0x61707865;
+        x1 = 0x3320646e;
+        x2 = 0x79622d32;
+        x3 = 0x6b206574;
+        x4 = LE32(seed32[0]);
+        x5 = LE32(seed32[1]);
+        x6 = LE32(seed32[2]);
+        x7 = LE32(seed32[3]);
+        x8 = LE32(seed32[4]);
+        x9 = LE32(seed32[5]);
+        x10 = LE32(seed32[6]);
+        x11 = LE32(seed32[7]);
+        x12 = idx;
+        x13 = idx >> 32;
+        x14 = 0;
+        x15 = over_count;
+
+        n = 10;
+        while (n--) {
+            QUARTERROUND(x0, x4, x8,x12)
+            QUARTERROUND(x1, x5, x9,x13)
+            QUARTERROUND(x2, x6,x10,x14)
+            QUARTERROUND(x3, x7,x11,x15)
+            QUARTERROUND(x0, x5,x10,x15)
+            QUARTERROUND(x1, x6,x11,x12)
+            QUARTERROUND(x2, x7, x8,x13)
+            QUARTERROUND(x3, x4, x9,x14)
+        }
+
+        x0 += 0x61707865;
+        x1 += 0x3320646e;
+        x2 += 0x79622d32;
+        x3 += 0x6b206574;
+        x4 += LE32(seed32[0]);
+        x5 += LE32(seed32[1]);
+        x6 += LE32(seed32[2]);
+        x7 += LE32(seed32[3]);
+        x8 += LE32(seed32[4]);
+        x9 += LE32(seed32[5]);
+        x10 += LE32(seed32[6]);
+        x11 += LE32(seed32[7]);
+        x12 += idx;
+        x13 += idx >> 32;
+        x14 += 0;
+        x15 += over_count;
+
+        r1->d[3] = LE32((uint64_t) x0) << 32 | LE32(x1);
+        r1->d[2] = LE32((uint64_t) x2) << 32 | LE32(x3);
+        r1->d[1] = LE32((uint64_t) x4) << 32 | LE32(x5);
+        r1->d[0] = LE32((uint64_t) x6) << 32 | LE32(x7);
+        r2->d[3] = LE32((uint64_t) x8) << 32 | LE32(x9);
+        r2->d[2] = LE32((uint64_t) x10) << 32 | LE32(x11);
+        r2->d[1] = LE32((uint64_t) x12) << 32 | LE32(x13);
+        r2->d[0] = LE32((uint64_t) x14) << 32 | LE32(x15);
+
+        over1 = secp256k1_scalar_check_overflow(r1);
+        over2 = secp256k1_scalar_check_overflow(r2);
+        over_count++;
+   } while (over1 | over2);
+}
+
+#undef ROTL32
+#undef QUARTERROUND
+#undef BE32
+#undef LE32
+
 #endif /* SECP256K1_SCALAR_REPR_IMPL_H */

src/scalar_8x32_impl.h

@@ -7,6 +7,8 @@
 #ifndef SECP256K1_SCALAR_REPR_IMPL_H
 #define SECP256K1_SCALAR_REPR_IMPL_H
 
+#include <string.h>
+
 /* Limbs of the secp256k1 order. */
 #define SECP256K1_N_0 ((uint32_t)0xD0364141UL)
 #define SECP256K1_N_1 ((uint32_t)0xBFD25E8CUL)
@@ -56,6 +58,17 @@ SECP256K1_INLINE static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsig
     r->d[7] = 0;
 }
 
+SECP256K1_INLINE static void secp256k1_scalar_set_u64(secp256k1_scalar *r, uint64_t v) {
+    r->d[0] = v;
+    r->d[1] = v >> 32;
+    r->d[2] = 0;
+    r->d[3] = 0;
+    r->d[4] = 0;
+    r->d[5] = 0;
+    r->d[6] = 0;
+    r->d[7] = 0;
+}
+
 SECP256K1_INLINE static unsigned int secp256k1_scalar_get_bits(const secp256k1_scalar *a, unsigned int offset, unsigned int count) {
     VERIFY_CHECK((offset + count - 1) >> 5 == offset >> 5);
     return (a->d[offset >> 5] >> (offset & 0x1F)) & ((1 << count) - 1);
@@ -718,4 +731,102 @@ SECP256K1_INLINE static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r,
     secp256k1_scalar_cadd_bit(r, 0, (l[(shift - 1) >> 5] >> ((shift - 1) & 0x1f)) & 1);
 }
 
+#define ROTL32(x,n) ((x) << (n) | (x) >> (32-(n)))
+#define QUARTERROUND(a,b,c,d) \
+  a += b; d = ROTL32(d ^ a, 16); \
+  c += d; b = ROTL32(b ^ c, 12); \
+  a += b; d = ROTL32(d ^ a, 8); \
+  c += d; b = ROTL32(b ^ c, 7);
+
+#ifdef WORDS_BIGENDIAN
+#define LE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
+#define BE32(p) (p)
+#else
+#define BE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
+#define LE32(p) (p)
+#endif
+
+static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx) {
+    size_t n;
+    size_t over_count = 0;
+    uint32_t seed32[8];
+    uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+    int over1, over2;
+
+    memcpy((void *) seed32, (const void *) seed, 32);
+    do {
+        x0 = 0x61707865;
+        x1 = 0x3320646e;
+        x2 = 0x79622d32;
+        x3 = 0x6b206574;
+        x4 = LE32(seed32[0]);
+        x5 = LE32(seed32[1]);
+        x6 = LE32(seed32[2]);
+        x7 = LE32(seed32[3]);
+        x8 = LE32(seed32[4]);
+        x9 = LE32(seed32[5]);
+        x10 = LE32(seed32[6]);
+        x11 = LE32(seed32[7]);
+        x12 = idx;
+        x13 = idx >> 32;
+        x14 = 0;
+        x15 = over_count;
+
+        n = 10;
+        while (n--) {
+            QUARTERROUND(x0, x4, x8,x12)
+            QUARTERROUND(x1, x5, x9,x13)
+            QUARTERROUND(x2, x6,x10,x14)
+            QUARTERROUND(x3, x7,x11,x15)
+            QUARTERROUND(x0, x5,x10,x15)
+            QUARTERROUND(x1, x6,x11,x12)
+            QUARTERROUND(x2, x7, x8,x13)
+            QUARTERROUND(x3, x4, x9,x14)
+        }
+
+        x0 += 0x61707865;
+        x1 += 0x3320646e;
+        x2 += 0x79622d32;
+        x3 += 0x6b206574;
+        x4 += LE32(seed32[0]);
+        x5 += LE32(seed32[1]);
+        x6 += LE32(seed32[2]);
+        x7 += LE32(seed32[3]);
+        x8 += LE32(seed32[4]);
+        x9 += LE32(seed32[5]);
+        x10 += LE32(seed32[6]);
+        x11 += LE32(seed32[7]);
+        x12 += idx;
+        x13 += idx >> 32;
+        x14 += 0;
+        x15 += over_count;
+
+        r1->d[7] = LE32(x0);
+        r1->d[6] = LE32(x1);
+        r1->d[5] = LE32(x2);
+        r1->d[4] = LE32(x3);
+        r1->d[3] = LE32(x4);
+        r1->d[2] = LE32(x5);
+        r1->d[1] = LE32(x6);
+        r1->d[0] = LE32(x7);
+        r2->d[7] = LE32(x8);
+        r2->d[6] = LE32(x9);
+        r2->d[5] = LE32(x10);
+        r2->d[4] = LE32(x11);
+        r2->d[3] = LE32(x12);
+        r2->d[2] = LE32(x13);
+        r2->d[1] = LE32(x14);
+        r2->d[0] = LE32(x15);
+
+        over1 = secp256k1_scalar_check_overflow(r1);
+        over2 = secp256k1_scalar_check_overflow(r2);
+        over_count++;
+   } while (over1 | over2);
+}
+
+#undef ROTL32
+#undef QUARTERROUND
+#undef BE32
+#undef LE32
+
 #endif /* SECP256K1_SCALAR_REPR_IMPL_H */

src/scalar_low_impl.h

@@ -17,6 +17,7 @@ SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a)
 
 SECP256K1_INLINE static void secp256k1_scalar_clear(secp256k1_scalar *r) { *r = 0; }
 SECP256K1_INLINE static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsigned int v) { *r = v; }
+SECP256K1_INLINE static void secp256k1_scalar_set_u64(secp256k1_scalar *r, uint64_t v) { *r = v % EXHAUSTIVE_TEST_ORDER; }
 
 SECP256K1_INLINE static unsigned int secp256k1_scalar_get_bits(const secp256k1_scalar *a, unsigned int offset, unsigned int count) {
     if (offset < 32)
@@ -111,4 +112,9 @@ SECP256K1_INLINE static int secp256k1_scalar_eq(const secp256k1_scalar *a, const
     return *a == *b;
 }
 
+SECP256K1_INLINE static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t n) {
+    *r1 = (seed[0] + n) % EXHAUSTIVE_TEST_ORDER;
+    *r2 = (seed[1] + n) % EXHAUSTIVE_TEST_ORDER;
+}
+
 #endif /* SECP256K1_SCALAR_REPR_IMPL_H */

src/secp256k1.c

@@ -20,6 +20,16 @@
 #include "hash_impl.h"
 #include "scratch_impl.h"
 
+#ifdef ENABLE_MODULE_GENERATOR
+# include "include/secp256k1_generator.h"
+#endif
+
+#ifdef ENABLE_MODULE_RANGEPROOF
+# include "include/secp256k1_rangeproof.h"
+# include "modules/rangeproof/pedersen.h"
+# include "modules/rangeproof/rangeproof.h"
+#endif
+
 #define ARG_CHECK(cond) do { \
     if (EXPECT(!(cond), 0)) { \
         secp256k1_callback_call(&ctx->illegal_callback, #cond); \
@@ -413,6 +423,27 @@ static SECP256K1_INLINE void buffer_append(unsigned char *buf, unsigned int *off
     *offset += len;
 }
 
+/* This nonce function is described in BIP-schnorr
+ * (https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki) */
+static int secp256k1_nonce_function_bipschnorr(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
+    secp256k1_sha256 sha;
+    (void) data;
+    (void) counter;
+    VERIFY_CHECK(counter == 0);
+
+    /* Hash x||msg as per the spec */
+    secp256k1_sha256_initialize(&sha);
+    secp256k1_sha256_write(&sha, key32, 32);
+    secp256k1_sha256_write(&sha, msg32, 32);
+    /* Hash in algorithm, which is not in the spec, but may be critical to
+     * users depending on it to avoid nonce reuse across algorithms. */
+    if (algo16 != NULL) {
+        secp256k1_sha256_write(&sha, algo16, 16);
+    }
+    secp256k1_sha256_finalize(&sha, nonce32);
+    return 1;
+}
+
 static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
    unsigned char keydata[112];
    unsigned int offset = 0;
@@ -685,6 +716,30 @@ int secp256k1_ec_pubkey_combine(const secp256k1_context* ctx, secp256k1_pubkey *
 # include "modules/ecdh/main_impl.h"
 #endif
 
+#ifdef ENABLE_MODULE_SCHNORRSIG
+# include "modules/schnorrsig/main_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_MUSIG
+# include "modules/musig/main_impl.h"
+#endif
+
 #ifdef ENABLE_MODULE_RECOVERY
 # include "modules/recovery/main_impl.h"
 #endif
+
+#ifdef ENABLE_MODULE_GENERATOR
+# include "modules/generator/main_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_RANGEPROOF
+# include "modules/rangeproof/main_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_WHITELIST
+# include "modules/whitelist/main_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_SURJECTIONPROOF
+# include "modules/surjection/main_impl.h"
+#endif

src/testrand.h

@@ -35,4 +35,7 @@ static void secp256k1_rand256_test(unsigned char *b32);
 /** Generate pseudorandom bytes with long sequences of zero and one bits. */
 static void secp256k1_rand_bytes_test(unsigned char *bytes, size_t len);
 
+/** Generate a pseudorandom 64-bit integer in the range min..max, inclusive. */
+static int64_t secp256k1_rands64(uint64_t min, uint64_t max);
+
 #endif /* SECP256K1_TESTRAND_H */

src/testrand_impl.h

@@ -1,5 +1,5 @@
 /**********************************************************************
- * Copyright (c) 2013-2015 Pieter Wuille                              *
+ * Copyright (c) 2013-2015 Pieter Wuille, Gregory Maxwell             *
  * Distributed under the MIT software license, see the accompanying   *
  * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
  **********************************************************************/
@@ -107,4 +107,21 @@ static void secp256k1_rand256_test(unsigned char *b32) {
     secp256k1_rand_bytes_test(b32, 32);
 }
 
+SECP256K1_INLINE static int64_t secp256k1_rands64(uint64_t min, uint64_t max) {
+    uint64_t range;
+    uint64_t r;
+    uint64_t clz;
+    VERIFY_CHECK(max >= min);
+    if (max == min) {
+        return min;
+    }
+    range = max - min;
+    clz = secp256k1_clz64_var(range);
+    do {
+        r = ((uint64_t)secp256k1_rand32() << 32) | secp256k1_rand32();
+        r >>= clz;
+    } while (r > range);
+    return min + (int64_t)r;
+}
+
 #endif /* SECP256K1_TESTRAND_IMPL_H */

src/tests.c

@@ -1,5 +1,5 @@
 /**********************************************************************
- * Copyright (c) 2013, 2014, 2015 Pieter Wuille, Gregory Maxwell      *
+ * Copyright (c) 2013-2015 Pieter Wuille, Gregory Maxwell             *
  * Distributed under the MIT software license, see the accompanying   *
  * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
  **********************************************************************/
@@ -140,6 +140,52 @@ void random_scalar_order(secp256k1_scalar *num) {
     } while(1);
 }
 
+void run_util_tests(void) {
+    int i;
+    uint64_t r;
+    uint64_t r2;
+    uint64_t r3;
+    int64_t s;
+    CHECK(secp256k1_clz64_var(0) == 64);
+    CHECK(secp256k1_clz64_var(1) == 63);
+    CHECK(secp256k1_clz64_var(2) == 62);
+    CHECK(secp256k1_clz64_var(3) == 62);
+    CHECK(secp256k1_clz64_var(~0ULL) == 0);
+    CHECK(secp256k1_clz64_var((~0ULL) - 1) == 0);
+    CHECK(secp256k1_clz64_var((~0ULL) >> 1) == 1);
+    CHECK(secp256k1_clz64_var((~0ULL) >> 2) == 2);
+    CHECK(secp256k1_sign_and_abs64(&r, INT64_MAX) == 0);
+    CHECK(r == INT64_MAX);
+    CHECK(secp256k1_sign_and_abs64(&r, INT64_MAX - 1) == 0);
+    CHECK(r == INT64_MAX - 1);
+    CHECK(secp256k1_sign_and_abs64(&r, INT64_MIN) == 1);
+    CHECK(r == (uint64_t)INT64_MAX + 1);
+    CHECK(secp256k1_sign_and_abs64(&r, INT64_MIN + 1) == 1);
+    CHECK(r == (uint64_t)INT64_MAX);
+    CHECK(secp256k1_sign_and_abs64(&r, 0) == 0);
+    CHECK(r == 0);
+    CHECK(secp256k1_sign_and_abs64(&r, 1) == 0);
+    CHECK(r == 1);
+    CHECK(secp256k1_sign_and_abs64(&r, -1) == 1);
+    CHECK(r == 1);
+    CHECK(secp256k1_sign_and_abs64(&r, 2) == 0);
+    CHECK(r == 2);
+    CHECK(secp256k1_sign_and_abs64(&r, -2) == 1);
+    CHECK(r == 2);
+    for (i = 0; i < 10; i++) {
+        CHECK(secp256k1_clz64_var((~0ULL) - secp256k1_rand32()) == 0);
+        r = ((uint64_t)secp256k1_rand32() << 32) | secp256k1_rand32();
+        r2 = secp256k1_rands64(0, r);
+        CHECK(r2 <= r);
+        r3 = secp256k1_rands64(r2, r);
+        CHECK((r3 >= r2) && (r3 <= r));
+        r = secp256k1_rands64(0, INT64_MAX);
+        s = (int64_t)r * (secp256k1_rand32()&1?-1:1);
+        CHECK(secp256k1_sign_and_abs64(&r2, s) == (s < 0));
+        CHECK(r2 == r);
+    }
+}
+
 void run_context_tests(int use_prealloc) {
     secp256k1_pubkey pubkey;
     secp256k1_pubkey zero_pubkey;
@@ -1077,12 +1123,122 @@ void scalar_test(void) {
 
 }
 
+void scalar_chacha_tests(void) {
+    /* Test vectors 1 to 4 from https://tools.ietf.org/html/rfc8439#appendix-A
+     * Note that scalar_set_b32 and scalar_get_b32 represent integers
+     * underlying the scalar in big-endian format. */
+    unsigned char expected1[64] = {
+        0xad, 0xe0, 0xb8, 0x76, 0x90, 0x3d, 0xf1, 0xa0,
+        0xe5, 0x6a, 0x5d, 0x40, 0x28, 0xbd, 0x86, 0x53,
+        0xb8, 0x19, 0xd2, 0xbd, 0x1a, 0xed, 0x8d, 0xa0,
+        0xcc, 0xef, 0x36, 0xa8, 0xc7, 0x0d, 0x77, 0x8b,
+        0x7c, 0x59, 0x41, 0xda, 0x8d, 0x48, 0x57, 0x51,
+        0x3f, 0xe0, 0x24, 0x77, 0x37, 0x4a, 0xd8, 0xb8,
+        0xf4, 0xb8, 0x43, 0x6a, 0x1c, 0xa1, 0x18, 0x15,
+        0x69, 0xb6, 0x87, 0xc3, 0x86, 0x65, 0xee, 0xb2
+    };
+    unsigned char expected2[64] = {
+        0xbe, 0xe7, 0x07, 0x9f, 0x7a, 0x38, 0x51, 0x55,
+        0x7c, 0x97, 0xba, 0x98, 0x0d, 0x08, 0x2d, 0x73,
+        0xa0, 0x29, 0x0f, 0xcb, 0x69, 0x65, 0xe3, 0x48,
+        0x3e, 0x53, 0xc6, 0x12, 0xed, 0x7a, 0xee, 0x32,
+        0x76, 0x21, 0xb7, 0x29, 0x43, 0x4e, 0xe6, 0x9c,
+        0xb0, 0x33, 0x71, 0xd5, 0xd5, 0x39, 0xd8, 0x74,
+        0x28, 0x1f, 0xed, 0x31, 0x45, 0xfb, 0x0a, 0x51,
+        0x1f, 0x0a, 0xe1, 0xac, 0x6f, 0x4d, 0x79, 0x4b
+    };
+    unsigned char seed3[32] = {
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01
+    };
+    unsigned char expected3[64] = {
+        0x24, 0x52, 0xeb, 0x3a, 0x92, 0x49, 0xf8, 0xec,
+        0x8d, 0x82, 0x9d, 0x9b, 0xdd, 0xd4, 0xce, 0xb1,
+        0xe8, 0x25, 0x20, 0x83, 0x60, 0x81, 0x8b, 0x01,
+        0xf3, 0x84, 0x22, 0xb8, 0x5a, 0xaa, 0x49, 0xc9,
+        0xbb, 0x00, 0xca, 0x8e, 0xda, 0x3b, 0xa7, 0xb4,
+        0xc4, 0xb5, 0x92, 0xd1, 0xfd, 0xf2, 0x73, 0x2f,
+        0x44, 0x36, 0x27, 0x4e, 0x25, 0x61, 0xb3, 0xc8,
+        0xeb, 0xdd, 0x4a, 0xa6, 0xa0, 0x13, 0x6c, 0x00
+    };
+    unsigned char seed4[32] = {
+        0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+    };
+    unsigned char expected4[64] = {
+        0xfb, 0x4d, 0xd5, 0x72, 0x4b, 0xc4, 0x2e, 0xf1,
+        0xdf, 0x92, 0x26, 0x36, 0x32, 0x7f, 0x13, 0x94,
+        0xa7, 0x8d, 0xea, 0x8f, 0x5e, 0x26, 0x90, 0x39,
+        0xa1, 0xbe, 0xbb, 0xc1, 0xca, 0xf0, 0x9a, 0xae,
+        0xa2, 0x5a, 0xb2, 0x13, 0x48, 0xa6, 0xb4, 0x6c,
+        0x1b, 0x9d, 0x9b, 0xcb, 0x09, 0x2c, 0x5b, 0xe6,
+        0x54, 0x6c, 0xa6, 0x24, 0x1b, 0xec, 0x45, 0xd5,
+        0x87, 0xf4, 0x74, 0x73, 0x96, 0xf0, 0x99, 0x2e
+    };
+    unsigned char seed5[32] = {
+        0x32, 0x56, 0x56, 0xf4, 0x29, 0x02, 0xc2, 0xf8,
+        0xa3, 0x4b, 0x96, 0xf5, 0xa7, 0xf7, 0xe3, 0x6c,
+        0x92, 0xad, 0xa5, 0x18, 0x1c, 0xe3, 0x41, 0xae,
+        0xc3, 0xf3, 0x18, 0xd0, 0xfa, 0x5b, 0x72, 0x53
+    };
+    unsigned char expected5[64] = {
+        0xe7, 0x56, 0xd3, 0x28, 0xe9, 0xc6, 0x19, 0x5c,
+        0x6f, 0x17, 0x8e, 0x21, 0x8c, 0x1e, 0x72, 0x11,
+        0xe7, 0xbd, 0x17, 0x0d, 0xac, 0x14, 0xad, 0xe9,
+        0x3d, 0x9f, 0xb6, 0x92, 0xd6, 0x09, 0x20, 0xfb,
+        0x43, 0x8e, 0x3b, 0x6d, 0xe3, 0x33, 0xdc, 0xc7,
+        0x6c, 0x07, 0x6f, 0xbb, 0x1f, 0xb4, 0xc8, 0xb5,
+        0xe3, 0x6c, 0xe5, 0x12, 0xd9, 0xd7, 0x64, 0x0c,
+        0xf5, 0xa7, 0x0d, 0xab, 0x79, 0x03, 0xf1, 0x81
+    };
+
+    secp256k1_scalar exp_r1, exp_r2;
+    secp256k1_scalar r1, r2;
+    unsigned char seed0[32] = { 0 };
+
+    secp256k1_scalar_chacha20(&r1, &r2, seed0, 0);
+    secp256k1_scalar_set_b32(&exp_r1, &expected1[0], NULL);
+    secp256k1_scalar_set_b32(&exp_r2, &expected1[32], NULL);
+    CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
+    CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
+
+    secp256k1_scalar_chacha20(&r1, &r2, seed0, 1);
+    secp256k1_scalar_set_b32(&exp_r1, &expected2[0], NULL);
+    secp256k1_scalar_set_b32(&exp_r2, &expected2[32], NULL);
+    CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
+    CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
+
+    secp256k1_scalar_chacha20(&r1, &r2, seed3, 1);
+    secp256k1_scalar_set_b32(&exp_r1, &expected3[0], NULL);
+    secp256k1_scalar_set_b32(&exp_r2, &expected3[32], NULL);
+    CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
+    CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
+
+    secp256k1_scalar_chacha20(&r1, &r2, seed4, 2);
+    secp256k1_scalar_set_b32(&exp_r1, &expected4[0], NULL);
+    secp256k1_scalar_set_b32(&exp_r2, &expected4[32], NULL);
+    CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
+    CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
+
+    secp256k1_scalar_chacha20(&r1, &r2, seed5, 0x6ff8602a7a78e2f2ULL);
+    secp256k1_scalar_set_b32(&exp_r1, &expected5[0], NULL);
+    secp256k1_scalar_set_b32(&exp_r2, &expected5[32], NULL);
+    CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
+    CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
+}
+
 void run_scalar_tests(void) {
     int i;
     for (i = 0; i < 128 * count; i++) {
         scalar_test();
     }
 
+    scalar_chacha_tests();
+
     {
         /* (-1)+1 should be zero. */
         secp256k1_scalar s, o;
@@ -5162,10 +5318,34 @@ void run_ecdsa_openssl(void) {
 # include "modules/ecdh/tests_impl.h"
 #endif
 
+#ifdef ENABLE_MODULE_SCHNORRSIG
+# include "modules/schnorrsig/tests_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_MUSIG
+# include "modules/musig/tests_impl.h"
+#endif
+
 #ifdef ENABLE_MODULE_RECOVERY
 # include "modules/recovery/tests_impl.h"
 #endif
 
+#ifdef ENABLE_MODULE_GENERATOR
+# include "modules/generator/tests_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_RANGEPROOF
+# include "modules/rangeproof/tests_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_WHITELIST
+# include "modules/whitelist/tests_impl.h"
+#endif
+
+#ifdef ENABLE_MODULE_SURJECTIONPROOF
+# include "modules/surjection/tests_impl.h"
+#endif
+
 int main(int argc, char **argv) {
     unsigned char seed16[16] = {0};
     unsigned char run32[32] = {0};
@@ -5223,6 +5403,7 @@ int main(int argc, char **argv) {
 
     run_rand_bits();
     run_rand_int();
+    run_util_tests();
 
     run_sha256_tests();
     run_hmac_sha256_tests();
@@ -5275,6 +5456,15 @@ int main(int argc, char **argv) {
     run_ecdh_tests();
 #endif
 
+#ifdef ENABLE_MODULE_SCHNORRSIG
+    /* Schnorrsig tests */
+    run_schnorrsig_tests();
+#endif
+
+#ifdef ENABLE_MODULE_MUSIG
+    run_musig_tests();
+#endif
+
     /* ecdsa tests */
     run_random_pubkeys();
     run_ecdsa_der_parse();
@@ -5290,6 +5480,23 @@ int main(int argc, char **argv) {
     run_recovery_tests();
 #endif
 
+#ifdef ENABLE_MODULE_GENERATOR
+    run_generator_tests();
+#endif
+
+#ifdef ENABLE_MODULE_RANGEPROOF
+    run_rangeproof_tests();
+#endif
+
+#ifdef ENABLE_MODULE_WHITELIST
+    /* Key whitelisting tests */
+    run_whitelist_tests();
+#endif
+
+#ifdef ENABLE_MODULE_SURJECTIONPROOF
+    run_surjection_tests();
+#endif
+
     secp256k1_rand256(run32);
     printf("random run = %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n", run32[0], run32[1], run32[2], run32[3], run32[4], run32[5], run32[6], run32[7], run32[8], run32[9], run32[10], run32[11], run32[12], run32[13], run32[14], run32[15]);
 

src/util.h

@@ -1,5 +1,5 @@
 /**********************************************************************
- * Copyright (c) 2013, 2014 Pieter Wuille                             *
+ * Copyright (c) 2013-2015 Pieter Wuille, Gregory Maxwell             *
  * Distributed under the MIT software license, see the accompanying   *
  * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
  **********************************************************************/
@@ -125,6 +125,32 @@ static SECP256K1_INLINE void *manual_alloc(void** prealloc_ptr, size_t alloc_siz
     return ret;
 }
 
+/* Extract the sign of an int64, take the abs and return a uint64, constant time. */
+SECP256K1_INLINE static int secp256k1_sign_and_abs64(uint64_t *out, int64_t in) {
+    uint64_t mask0, mask1;
+    int ret;
+    ret = in < 0;
+    mask0 = ret + ~((uint64_t)0);
+    mask1 = ~mask0;
+    *out = (uint64_t)in;
+    *out = (*out & mask0) | ((~*out + 1) & mask1);
+    return ret;
+}
+
+SECP256K1_INLINE static int secp256k1_clz64_var(uint64_t x) {
+    int ret;
+    if (!x) {
+        return 64;
+    }
+# if defined(HAVE_BUILTIN_CLZLL)
+    ret = __builtin_clzll(x);
+# else
+    /*FIXME: debruijn fallback. */
+    for (ret = 0; ((x & (1ULL << 63)) == 0); x <<= 1, ret++);
+# endif
+    return ret;
+}
+
 /* Macro for restrict, when available and not in a VERIFY build. */
 #if defined(SECP256K1_BUILD) && defined(VERIFY)
 # define SECP256K1_RESTRICT