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Add support for Schnorr crypto (BCH variant)

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Support Schnorr signature and verification defined in
https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/2019-05-15-schnorr.md.

The implementation is based on https://github.com/Bitcoin-ABC/secp256k1
as well as the test vectors.
This commit is contained in:
Fabien 2019-04-20 17:01:04 +03:00 committed by Pavol Rusnak
parent d6d1cd7b4c
commit 9ef26c347e
5 changed files with 482 additions and 0 deletions
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1
crypto/Makefile
View File

@ -79,6 +79,7 @@ SRCS += shamir.c
SRCS += hmac_drbg.c
SRCS += rfc6979.c
SRCS += slip39.c
SRCS += schnorr.c
OBJS = $(SRCS:.c=.o)

1
crypto/README.md
View File

@ -12,6 +12,7 @@ These include:
- ECDSA signing/verifying (supports secp256k1 and nist256p1 curves,
uses RFC6979 for deterministic signatures)
- ECDSA public key derivation
- Schnorr (BCH variant) signing/verifying
- Base32 (RFC4648 and custom alphabets)
- Base58 address representation
- Ed25519 signing/verifying (also SHA3 and Keccak variants)

213
crypto/schnorr.c Normal file
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@ -0,0 +1,213 @@
/**
* Copyright (c) 2021 The Bitcoin ABC developers
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "schnorr.h"
#include "hmac_drbg.h"
#include "memzero.h"
#include "rfc6979.h"
#include <assert.h>
#include <stdio.h>
#include <string.h>
static int jacobi(const bignum256 *_n, const bignum256 *_k) {
assert(!bn_is_zero(_k) && bn_is_odd(_k));
bignum256 n_copy = {0};
bignum256 *n = &n_copy;
bn_copy(_n, n);
bignum256 k_copy = {0};
bignum256 *k = &k_copy;
bn_copy(_k, k);
int t = 0;
while (!bn_is_zero(n)) {
while (bn_is_even(n)) {
// jacobi(2 * n, k) = jacobi(n, k) if k = 1 (mod 8) or k = 7 (mod 8)
// jacobi(2 * n, k) = -jacobi(n, k) if k = 3 (mod 8) or k = 5 (mod 8)
uint32_t r = k->val[0] & 0x07;
t ^= (r == 3 || r == 5);
bn_rshift(n);
}
if (bn_is_less(n, k)) {
// jacobi(n, k) = jacobi(k, n) if k = n = 1 (mod 4)
// jacobi(n, k) = -jacobi(k, n) if k = n = 3 (mod 4)
t ^= ((n->val[0] & k->val[0] & 3) == 3);
bignum256 *temp = n;
n = k;
k = temp;
}
// jacobi(n, k) = jacobi(n - k, k)
bn_subtract(n, k, n);
}
int k_is_one = bn_is_one(k);
// Cleanup
memzero(&n_copy, sizeof(n_copy));
memzero(&k_copy, sizeof(k_copy));
// Map t: [0] => 1, [1] => -1
t = -2 * t + 1;
return k_is_one * t;
}
static int is_non_quad_residue(const bignum256 *n, const bignum256 *prime) {
return jacobi(n, prime) == -1;
}
static int generate_k_schnorr(const ecdsa_curve *curve, const uint8_t *priv_key,
const uint8_t *hash, bignum256 *k) {
rfc6979_state rng = {0};
uint8_t hmac_data[SHA256_DIGEST_LENGTH + 16] = {0};
/*
* Init the HMAC with additional data specific to Schnorr. This prevents from
* leaking the private key in the case the same message is signed with both
* Schnorr and ECDSA.
*/
memcpy(hmac_data, hash, SHA256_DIGEST_LENGTH);
memcpy(hmac_data + SHA256_DIGEST_LENGTH, "Schnorr+SHA256 ", 16);
hmac_drbg_init(&rng, priv_key, 32, hmac_data, SHA256_DIGEST_LENGTH + 16);
for (int i = 0; i < 10000; i++) {
generate_k_rfc6979(k, &rng);
// If k is too big or too small, we don't like it
if (bn_is_zero(k) || !bn_is_less(k, &curve->order)) {
continue;
}
memzero(&rng, sizeof(rng));
return 0;
}
memzero(&rng, sizeof(rng));
return 1;
}
// e = H(Rx, pub_key, msg_hash)
static void calc_e(const ecdsa_curve *curve, const bignum256 *Rx,
const uint8_t pub_key[33], const uint8_t *msg_hash,
bignum256 *e) {
uint8_t Rxbuf[32] = {0};
SHA256_CTX ctx = {0};
uint8_t digest[SHA256_DIGEST_LENGTH] = {0};
bn_write_be(Rx, Rxbuf);
sha256_Init(&ctx);
sha256_Update(&ctx, Rxbuf, sizeof(Rxbuf));
sha256_Update(&ctx, pub_key, 33);
sha256_Update(&ctx, msg_hash, SHA256_DIGEST_LENGTH);
sha256_Final(&ctx, digest);
bn_read_be(digest, e);
bn_fast_mod(e, &curve->order);
bn_mod(e, &curve->order);
}
int schnorr_sign_digest(const ecdsa_curve *curve, const uint8_t *priv_key,
const uint8_t *digest, uint8_t *sign) {
uint8_t pub_key[33] = {0};
curve_point R = {0};
bignum256 e = {0}, s = {0}, k = {0};
ecdsa_get_public_key33(curve, priv_key, pub_key);
// Compute k
if (generate_k_schnorr(curve, priv_key, digest, &k) != 0) {
memzero(&k, sizeof(k));
return 1;
}
// Compute R = k * G
scalar_multiply(curve, &k, &R);
// If R.y is not a quadratic residue, negate the nonce
bn_cnegate(is_non_quad_residue(&R.y, &curve->prime), &k, &curve->order);
bn_write_be(&R.x, sign);
// Compute e = H(Rx, pub_key, msg_hash)
calc_e(curve, &R.x, pub_key, digest, &e);
// Compute s = k + e * priv_key
bn_read_be(priv_key, &s);
bn_multiply(&e, &s, &curve->order);
bn_addmod(&s, &k, &curve->order);
memzero(&k, sizeof(k));
bn_mod(&s, &curve->order);
bn_write_be(&s, sign + 32);
return 0;
}
int schnorr_verify_digest(const ecdsa_curve *curve, const uint8_t *pub_key,
const uint8_t *digest, const uint8_t *sign) {
curve_point P = {0}, sG = {0}, R = {0};
bignum256 r = {0}, s = {0}, e = {0};
bn_read_be(sign, &r);
bn_read_be(sign + 32, &s);
// Signature is invalid if s >= n or r >= p.
if (!bn_is_less(&r, &curve->prime) || !bn_is_less(&s, &curve->order)) {
return 1;
}
if (!ecdsa_read_pubkey(curve, pub_key, &P)) {
return 2;
}
// Compute e
calc_e(curve, &r, pub_key, digest, &e);
if (bn_is_zero(&e)) {
return 3;
}
// Compute R = sG - eP
bn_subtract(&curve->order, &e, &e);
scalar_multiply(curve, &s, &sG);
point_multiply(curve, &e, &P, &R);
point_add(curve, &sG, &R);
if (point_is_infinity(&R)) {
return 4;
}
// Check r == Rx
if (!bn_is_equal(&r, &R.x)) {
return 5;
}
// Check Ry is a quadratic residue
if (is_non_quad_residue(&R.y, &curve->prime)) {
return 6;
}
return 0;
}

36
crypto/schnorr.h Normal file
View File

@ -0,0 +1,36 @@
/**
* Copyright (c) 2021 The Bitcoin ABC developers
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef __SCHNORR_H__
#define __SCHNORR_H__
#include "ecdsa.h"
/* A Schnorr signature is always 64 bytes */
#define SCHNORR_SIG_LENGTH 64
// sign/verify returns 0 if operation succeeded
int schnorr_sign_digest(const ecdsa_curve *curve, const uint8_t *priv_key,
const uint8_t *digest, uint8_t *result);
int schnorr_verify_digest(const ecdsa_curve *curve, const uint8_t *pub_key,
const uint8_t *msg_hash, const uint8_t *sign);
#endif

231
crypto/tests/test_check.c
View File

@ -63,6 +63,7 @@
#include "rand.h"
#include "rc4.h"
#include "rfc6979.h"
#include "schnorr.h"
#include "script.h"
#include "secp256k1.h"
#include "sha2.h"
@ -8656,6 +8657,231 @@ START_TEST(test_compress_coords) {
}
END_TEST
START_TEST(test_schnorr_sign_verify_digest) {
static struct {
const char *digest;
const char *priv_key;
const char *sig;
} tests[] = {
{
/* Very deterministic message */
"5255683DA567900BFD3E786ED8836A4E7763C221BF1AC20ECE2A5171B9199E8A",
"12B004FFF7F4B69EF8650E767F18F11EDE158148B425660723B9F9A66E61F747",
"2C56731AC2F7A7E7F11518FC7722A166B02438924CA9D8B4D111347B81D07175"
"71846DE67AD3D913A8FDF9D8F3F73161A4C48AE81CB183B214765FEB86E255CE",
},
};
const ecdsa_curve *curve = &secp256k1;
uint8_t digest[SHA256_DIGEST_LENGTH] = {0};
uint8_t priv_key[32] = {0};
uint8_t pub_key[33] = {0};
uint8_t result[SCHNORR_SIG_LENGTH] = {0};
uint8_t expected[SCHNORR_SIG_LENGTH] = {0};
int res = 0;
for (size_t i = 0; i < sizeof(tests) / sizeof(*tests); i++) {
memcpy(digest, fromhex(tests[i].digest), SHA256_DIGEST_LENGTH);
memcpy(priv_key, fromhex(tests[i].priv_key), 32);
memcpy(expected, fromhex(tests[i].sig), SCHNORR_SIG_LENGTH);
ecdsa_get_public_key33(curve, priv_key, pub_key);
schnorr_sign_digest(curve, priv_key, digest, result);
ck_assert_mem_eq(expected, result, SCHNORR_SIG_LENGTH);
res = schnorr_verify_digest(curve, pub_key, digest, result);
ck_assert_int_eq(res, 0);
}
}
END_TEST
START_TEST(test_schnorr_verify_digest) {
static struct {
const char *digest;
const char *pub_key;
const char *sig;
const int res;
} tests[] = {
{
/* Very deterministic message */
"5255683DA567900BFD3E786ED8836A4E7763C221BF1AC20ECE2A5171B9199E8A",
"030B4C866585DD868A9D62348A9CD008D6A312937048FFF31670E7E920CFC7A744",
"2C56731AC2F7A7E7F11518FC7722A166B02438924CA9D8B4D111347B81D07175"
"71846DE67AD3D913A8FDF9D8F3F73161A4C48AE81CB183B214765FEB86E255CE",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 1.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"0000000000000000000000000000000000000000000000000000000000000000",
"0279BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798",
"787A848E71043D280C50470E8E1532B2DD5D20EE912A45DBDD2BD1DFBF187EF6"
"7031A98831859DC34DFFEEDDA86831842CCD0079E1F92AF177F7F22CC1DCED05",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 2.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"2A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"1E51A22CCEC35599B8F266912281F8365FFC2D035A230434A1A64DC59F7013FD",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 3.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"5E2D58D8B3BCDF1ABADEC7829054F90DDA9805AAB56C77333024B9D0A508B75C",
"03FAC2114C2FBB091527EB7C64ECB11F8021CB45E8E7809D3C0938E4B8C0E5F84B",
"00DA9B08172A9B6F0466A2DEFD817F2D7AB437E0D253CB5395A963866B3574BE"
"00880371D01766935B92D2AB4CD5C8A2A5837EC57FED7660773A05F0DE142380",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 4.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"4DF3C3F68FCC83B27E9D42C90431A72499F17875C81A599B566C9889B9696703",
"03DEFDEA4CDB677750A420FEE807EACF21EB9898AE79B9768766E4FAA04A2D4A34",
"00000000000000000000003B78CE563F89A0ED9414F5AA28AD0D96D6795F9C63"
"02A8DC32E64E86A333F20EF56EAC9BA30B7246D6D25E22ADB8C6BE1AEB08D49D",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 4b.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"0000000000000000000000000000000000000000000000000000000000000000",
"031B84C5567B126440995D3ED5AABA0565D71E1834604819FF9C17F5E9D5DD078F",
"52818579ACA59767E3291D91B76B637BEF062083284992F2D95F564CA6CB4E35"
"30B1DA849C8E8304ADC0CFE870660334B3CFC18E825EF1DB34CFAE3DFC5D8187",
0, /* Success */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 6.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"2A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"FA16AEE06609280A19B67A24E1977E4697712B5FD2943914ECD5F730901B4AB7",
6, /* R.y is not a quadratic residue */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 7.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"5E2D58D8B3BCDF1ABADEC7829054F90DDA9805AAB56C77333024B9D0A508B75C",
"03FAC2114C2FBB091527EB7C64ECB11F8021CB45E8E7809D3C0938E4B8C0E5F84B",
"00DA9B08172A9B6F0466A2DEFD817F2D7AB437E0D253CB5395A963866B3574BE"
"D092F9D860F1776A1F7412AD8A1EB50DACCC222BC8C0E26B2056DF2F273EFDEC",
5, /* Negated message hash, R.x mismatch */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 8.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"0000000000000000000000000000000000000000000000000000000000000000",
"0279BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798",
"787A848E71043D280C50470E8E1532B2DD5D20EE912A45DBDD2BD1DFBF187EF6"
"8FCE5677CE7A623CB20011225797CE7A8DE1DC6CCD4F754A47DA6C600E59543C",
5, /* Negated s, R.x mismatch */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 9.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"03DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"2A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"1E51A22CCEC35599B8F266912281F8365FFC2D035A230434A1A64DC59F7013FD",
5, /* Negated P, R.x mismatch */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 10.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"2A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"8C3428869A663ED1E954705B020CBB3E7BB6AC31965B9EA4C73E227B17C5AF5A",
4, /* s * G = e * P, R = 0 */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 11.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"4A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"1E51A22CCEC35599B8F266912281F8365FFC2D035A230434A1A64DC59F7013FD",
5, /* R.x not on the curve, R.x mismatch */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 12.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFC2F"
"1E51A22CCEC35599B8F266912281F8365FFC2D035A230434A1A64DC59F7013FD",
1, /* r = p */
},
{
/*
* From Bitcoin ABC libsecp256k1, test vector 13.
* https://github.com/Bitcoin-ABC/secp256k1/blob/master/src/modules/schnorr/tests_impl.h
*/
"243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89",
"02DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659",
"2A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D"
"FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141",
1, /* s = n */
},
{
/* Very deterministic message */
"5255683DA567900BFD3E786ED8836A4E7763C221BF1AC20ECE2A5171B9199E8A",
"010B4C866585DD868A9D62348A9CD008D6A312937048FFF31670E7E920CFC7A744",
"2C56731AC2F7A7E7F11518FC7722A166B02438924CA9D8B4D111347B81D07175"
"71846DE67AD3D913A8FDF9D8F3F73161A4C48AE81CB183B214765FEB86E255CE",
2, /* Invalid public key */
},
};
const ecdsa_curve *curve = &secp256k1;
uint8_t digest[SHA256_DIGEST_LENGTH] = {0};
uint8_t pub_key[33] = {0};
uint8_t signature[SCHNORR_SIG_LENGTH] = {0};
int res = 0;
for (size_t i = 0; i < sizeof(tests) / sizeof(*tests); i++) {
memcpy(digest, fromhex(tests[i].digest), SHA256_DIGEST_LENGTH);
memcpy(pub_key, fromhex(tests[i].pub_key), 33);
memcpy(signature, fromhex(tests[i].sig), SCHNORR_SIG_LENGTH);
res = schnorr_verify_digest(curve, pub_key, digest, signature);
ck_assert_int_eq(res, tests[i].res);
}
}
END_TEST
static int my_strncasecmp(const char *s1, const char *s2, size_t n) {
size_t i = 0;
while (i < n) {
@ -8955,6 +9181,11 @@ Suite *test_suite(void) {
tcase_add_test(tc, test_compress_coords);
suite_add_tcase(s, tc);
tc = tcase_create("schnorr");
tcase_add_test(tc, test_schnorr_sign_verify_digest);
tcase_add_test(tc, test_schnorr_verify_digest);
suite_add_tcase(s, tc);
#if USE_CARDANO
tc = tcase_create("bip32-cardano");