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Add utilities from uncompressed Bulletproofs PR

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Add a transcript module for doing a generic Fiat Shamir
This commit is contained in:
sanket1729 2022-11-21 19:31:24 -08:00
parent 48563c8c79
commit 17417d44f3
5 changed files with 109 additions and 7 deletions
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4
src/modules/bulletproofs/Makefile.am.include
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@ -1,6 +1,8 @@
include_HEADERS += include/secp256k1_bulletproofs.h
noinst_HEADERS += src/modules/bulletproofs/tests_impl.h
noinst_HEADERS += src/modules/bulletproofs/bulletproofs_util.h
noinst_HEADERS += src/modules/bulletproofs/main_impl.h
noinst_HEADERS += src/modules/bulletproofs/bulletproofs_pp_transcript_impl.h
noinst_HEADERS += src/modules/bulletproofs/tests_impl.h
if USE_BENCHMARK
noinst_PROGRAMS += bench_bulletproofs

40
src/modules/bulletproofs/bulletproofs_pp_transcript_impl.h Normal file
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@ -0,0 +1,40 @@
/**********************************************************************
* Copyright (c) 2022 Sanket Kanjalkar *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
**********************************************************************/
#ifndef _SECP256K1_MODULE_BULLETPROOFS_PP_TRANSCRIPT_IMPL_
#define _SECP256K1_MODULE_BULLETPROOFS_PP_TRANSCRIPT_IMPL_
#include "group.h"
#include "scalar.h"
#include "bulletproofs_util.h"
/* Initializes SHA256 with fixed midstate. This midstate was computed by applying
* SHA256 to SHA256("Bulletproofs_pp/v0/commitment")||SHA256("Bulletproofs_pp/v0/commitment").
*/
static void secp256k1_bulletproofs_pp_sha256_tagged_commitment_init(secp256k1_sha256 *sha) {
secp256k1_sha256_initialize(sha);
sha->s[0] = 0x52fc8185ul;
sha->s[1] = 0x0e7debf0ul;
sha->s[2] = 0xb0967270ul;
sha->s[3] = 0x6f5abfe1ul;
sha->s[4] = 0x822bdec0ul;
sha->s[5] = 0x36db8beful;
sha->s[6] = 0x03d9e1f1ul;
sha->s[7] = 0x8a5cef6ful;
sha->bytes = 64;
}
/* Obtain a challenge scalar from the current transcript.*/
static void secp256k1_bulletproofs_challenge_scalar(secp256k1_scalar* ch, const secp256k1_sha256 *transcript, uint64_t idx) {
unsigned char buf[32];
secp256k1_sha256 sha = *transcript;
secp256k1_bulletproofs_le64(buf, idx);
secp256k1_sha256_write(&sha, buf, 8);
secp256k1_sha256_finalize(&sha, buf);
secp256k1_scalar_set_b32(ch, buf, NULL);
}
#endif

42
src/modules/bulletproofs/bulletproofs_util.h Normal file
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@ -0,0 +1,42 @@
/**********************************************************************
* Copyright (c) 2020 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_BULLETPROOFS_UTIL_
#define _SECP256K1_MODULE_BULLETPROOFS_UTIL_
#include "field.h"
#include "group.h"
#include "hash.h"
/* Outputs a pair of points, amortizing the parity byte between them
* Assumes both points' coordinates have been normalized.
*/
static void secp256k1_bulletproofs_serialize_points(unsigned char *output, const secp256k1_ge *lpt, const secp256k1_ge *rpt) {
output[0] = (secp256k1_fe_is_odd(&lpt->y) << 1) + secp256k1_fe_is_odd(&rpt->y);
secp256k1_fe_get_b32(&output[1], &lpt->x);
secp256k1_fe_get_b32(&output[33], &rpt->x);
}
/* Outputs a serialized point in compressed form. Returns 0 at point at infinity.
*/
static int secp256k1_bulletproofs_serialize_pt(unsigned char *output, secp256k1_ge *lpt) {
size_t size;
return secp256k1_eckey_pubkey_serialize(lpt, output, &size, 1 /*compressed*/);
}
/* little-endian encodes a uint64 */
static void secp256k1_bulletproofs_le64(unsigned char *output, const uint64_t n) {
output[0] = n;
output[1] = n >> 8;
output[2] = n >> 16;
output[3] = n >> 24;
output[4] = n >> 32;
output[5] = n >> 40;
output[6] = n >> 48;
output[7] = n >> 56;
}
#endif

13
src/modules/bulletproofs/main_impl.h
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@ -7,18 +7,19 @@
#ifndef _SECP256K1_MODULE_BULLETPROOFS_MAIN_
#define _SECP256K1_MODULE_BULLETPROOFS_MAIN_
#include "include/secp256k1_bulletproofs.h"
#include "include/secp256k1_generator.h"
#include "modules/generator/main_impl.h" /* for generator_{load, save} */
#include "hash.h"
#include "util.h"
/* this type must be completed before any of the modules/bulletproofs includes */
struct secp256k1_bulletproofs_generators {
size_t n;
/* n total generators; includes both G_i and H_i */
secp256k1_ge* gens;
};
#include "include/secp256k1_bulletproofs.h"
#include "include/secp256k1_generator.h"
#include "modules/generator/main_impl.h" /* for generator_{load, save} */
#include "hash.h"
#include "util.h"
secp256k1_bulletproofs_generators *secp256k1_bulletproofs_generators_create(const secp256k1_context *ctx, size_t n) {
secp256k1_bulletproofs_generators *ret;
secp256k1_rfc6979_hmac_sha256 rng;

17
src/modules/bulletproofs/tests_impl.h
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@ -7,6 +7,8 @@
#ifndef _SECP256K1_MODULE_BULLETPROOFS_TEST_
#define _SECP256K1_MODULE_BULLETPROOFS_TEST_
#include "bulletproofs_pp_transcript_impl.h"
static void test_bulletproofs_generators_api(void) {
/* The BP generator API requires no precomp */
secp256k1_context *none = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
@ -114,9 +116,24 @@ static void test_bulletproofs_generators_fixed(void) {
secp256k1_bulletproofs_generators_destroy(ctx, gens);
}
static void test_bulletproofs_pp_tagged_hash(void) {
unsigned char tag_data[29] = "Bulletproofs_pp/v0/commitment";
secp256k1_sha256 sha;
secp256k1_sha256 sha_cached;
unsigned char output[32];
unsigned char output_cached[32];
secp256k1_sha256_initialize_tagged(&sha, tag_data, sizeof(tag_data));
secp256k1_bulletproofs_pp_sha256_tagged_commitment_init(&sha_cached);
secp256k1_sha256_finalize(&sha, output);
secp256k1_sha256_finalize(&sha_cached, output_cached);
CHECK(secp256k1_memcmp_var(output, output_cached, 32) == 0);
}
void run_bulletproofs_tests(void) {
test_bulletproofs_generators_api();
test_bulletproofs_generators_fixed();
test_bulletproofs_pp_tagged_hash();
}
#endif