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schnorrsig: add extra parameter struct for sign_custom

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This simplifies the interface of sign_custom and allows adding more parameters
later in a backward compatible way.
This commit is contained in:
Jonas Nick
2020-11-02 14:41:25 +00:00
parent a0c3fc177f
commit d8d806aaf3
4 changed files with 75 additions and 20 deletions
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46
include/secp256k1_schnorrsig.h
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@@ -63,6 +63,35 @@ typedef int (*secp256k1_nonce_function_hardened)(
*/
SECP256K1_API extern const secp256k1_nonce_function_hardened secp256k1_nonce_function_bip340;
/** Data structure that contains additional arguments for schnorrsig_sign_custom.
*
* A schnorrsig_extraparams structure object can be initialized correctly by
* setting it to SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT.
*
* Members:
* magic: set to SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC at initialization
* and has no other function than making sure the object is
* initialized.
* noncefp: pointer to a nonce generation function. If NULL,
* secp256k1_nonce_function_bip340 is used
* ndata: pointer to arbitrary data used by the nonce generation function
* (can be NULL). If it is non-NULL and
* secp256k1_nonce_function_bip340 is used, then ndata must be a
* pointer to 32-byte auxiliary randomness as per BIP-340.
*/
typedef struct {
unsigned char magic[4];
secp256k1_nonce_function_hardened noncefp;
void* ndata;
} secp256k1_schnorrsig_extraparams;
#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC "\xda\x6f\xb3\x8c"
#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT {\
SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC,\
NULL,\
NULL\
}
/** Create a Schnorr signature.
*
* Does _not_ strictly follow BIP-340 because it does not verify the resulting
@@ -97,17 +126,15 @@ SECP256K1_API int secp256k1_schnorrsig_sign(
/** Create a Schnorr signature with a more flexible API.
*
* Same arguments as secp256k1_schnorrsig_sign except that it allows signing
* variable length messages and allows providing a different nonce derivation
* function with its own data argument.
* variable length messages and accepts a pointer to an extraparams object that
* allows customizing signing by passing additional arguments.
*
* Creates the same signatures as schnorrsig_sign if msglen is 32 and the
* extraparams.ndata is the same as aux_rand32.
*
* In: msg: the message being signed. Can only be NULL if msglen is 0.
* msglen: length of the message
* noncefp: pointer to a nonce generation function. If NULL,
* secp256k1_nonce_function_bip340 is used.
* ndata: pointer to arbitrary data used by the nonce generation function
* (can be NULL). If it is non-NULL and
* secp256k1_nonce_function_bip340 is used, then ndata must be a
* pointer to 32-byte auxiliary randomness as per BIP-340.
* extraparams: pointer to a extraparams object (can be NULL)
*/
SECP256K1_API int secp256k1_schnorrsig_sign_custom(
const secp256k1_context* ctx,
@@ -115,8 +142,7 @@ SECP256K1_API int secp256k1_schnorrsig_sign_custom(
const unsigned char *msg,
size_t msglen,
const secp256k1_keypair *keypair,
secp256k1_nonce_function_hardened noncefp,
void *ndata
secp256k1_schnorrsig_extraparams *extraparams
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(5);
/** Verify a Schnorr signature.