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schnorrsig: remove noncefp args from sign; add sign_custom function 

This makes the default sign function easier to use while allowing more granular
control through sign_custom.

Tests for sign_custom follow in a later commit.
This commit is contained in:
Jonas Nick 2020-10-30 17:48:16 +00:00
parent 442cee5baf
commit b6c0b72fb0
6 changed files with 52 additions and 31 deletions
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32
include/secp256k1_schnorrsig.h
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@ -66,22 +66,38 @@ SECP256K1_API extern const secp256k1_nonce_function_hardened secp256k1_nonce_fun
* signature. Instead, you can manually use secp256k1_schnorrsig_verify and
* abort if it fails.
*
* Otherwise BIP-340 compliant if the noncefp argument is NULL or
* secp256k1_nonce_function_bip340 and the ndata argument is 32-byte auxiliary
* randomness.
*
* Returns 1 on success, 0 on failure.
* Args: ctx: pointer to a context object, initialized for signing (cannot be NULL)
* Out: sig64: pointer to a 64-byte array to store the serialized signature (cannot be NULL)
* In: msg32: the 32-byte message being signed (cannot be NULL)
* keypair: pointer to an initialized keypair (cannot be NULL)
* 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
* aux_rand32: 32 bytes of fresh randomness. While recommended to provide
* this, it is only supplemental to security and can be NULL. See
* BIP-340 "Default Signing" for a full explanation of this
* argument and for guidance if randomness is expensive.
*/
SECP256K1_API int secp256k1_schnorrsig_sign(
const secp256k1_context* ctx,
unsigned char *sig64,
const unsigned char *msg32,
const secp256k1_keypair *keypair,
unsigned char *aux_rand32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Create a Schnorr signature with a more flexible API.
*
* Same arguments as secp256k1_schnorrsig_sign except that it misses aux_rand32
* and instead allows allows providing a different nonce derivation function
* with its own data argument.
*
* In: 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.
*/
SECP256K1_API int secp256k1_schnorrsig_sign(
SECP256K1_API int secp256k1_schnorrsig_sign_custom(
const secp256k1_context* ctx,
unsigned char *sig64,
const unsigned char *msg32,

4
src/bench_schnorrsig.c
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@ -32,7 +32,7 @@ void bench_schnorrsig_sign(void* arg, int iters) {
for (i = 0; i < iters; i++) {
msg[0] = i;
msg[1] = i >> 8;
CHECK(secp256k1_schnorrsig_sign(data->ctx, sig, msg, data->keypairs[i], NULL, NULL));
CHECK(secp256k1_schnorrsig_sign(data->ctx, sig, msg, data->keypairs[i], NULL));
}
}
@ -78,7 +78,7 @@ int main(void) {
data.sigs[i] = sig;
CHECK(secp256k1_keypair_create(data.ctx, keypair, sk));
CHECK(secp256k1_schnorrsig_sign(data.ctx, sig, msg, keypair, NULL, NULL));
CHECK(secp256k1_schnorrsig_sign(data.ctx, sig, msg, keypair, NULL));
CHECK(secp256k1_keypair_xonly_pub(data.ctx, &pk, NULL, keypair));
CHECK(secp256k1_xonly_pubkey_serialize(data.ctx, pk_char, &pk) == 1);
}

7
src/modules/schnorrsig/main_impl.h
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@ -120,7 +120,12 @@ static void secp256k1_schnorrsig_challenge(secp256k1_scalar* e, const unsigned c
secp256k1_scalar_set_b32(e, buf, NULL);
}
int secp256k1_schnorrsig_sign(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg32, const secp256k1_keypair *keypair, secp256k1_nonce_function_hardened noncefp, void *ndata) {
int secp256k1_schnorrsig_sign(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg32, const secp256k1_keypair *keypair, unsigned char *aux_rand32) {
return secp256k1_schnorrsig_sign_custom(ctx, sig64, msg32, keypair, NULL, aux_rand32);
}
int secp256k1_schnorrsig_sign_custom(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg32, const secp256k1_keypair *keypair, secp256k1_nonce_function_hardened noncefp, void *ndata) {
secp256k1_scalar sk;
secp256k1_scalar e;
secp256k1_scalar k;

2
src/modules/schnorrsig/tests_exhaustive_impl.h
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@ -163,7 +163,7 @@ static void test_exhaustive_schnorrsig_sign(const secp256k1_context *ctx, unsign
unsigned char expected_s_bytes[32];
secp256k1_scalar_get_b32(expected_s_bytes, &expected_s);
/* Invoke the real function to construct a signature. */
CHECK(secp256k1_schnorrsig_sign(ctx, sig64, msg32, &keypairs[d - 1], secp256k1_hardened_nonce_function_smallint, &k));
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig64, msg32, &keypairs[d - 1], secp256k1_hardened_nonce_function_smallint, &k));
/* The first 32 bytes must match the xonly pubkey for the specified k. */
CHECK(secp256k1_memcmp_var(sig64, xonly_pubkey_bytes[k - 1], 32) == 0);
/* The last 32 bytes must match the expected s value. */

34
src/modules/schnorrsig/tests_impl.h
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@ -143,23 +143,23 @@ void test_schnorrsig_api(void) {
/** main test body **/
ecount = 0;
CHECK(secp256k1_schnorrsig_sign(none, sig, msg, &keypairs[0], NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(none, sig, msg, &keypairs[0], NULL) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_schnorrsig_sign(vrfy, sig, msg, &keypairs[0], NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(vrfy, sig, msg, &keypairs[0], NULL) == 0);
CHECK(ecount == 2);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &keypairs[0], NULL, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &keypairs[0], NULL) == 1);
CHECK(ecount == 2);
CHECK(secp256k1_schnorrsig_sign(sign, NULL, msg, &keypairs[0], NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(sign, NULL, msg, &keypairs[0], NULL) == 0);
CHECK(ecount == 3);
CHECK(secp256k1_schnorrsig_sign(sign, sig, NULL, &keypairs[0], NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(sign, sig, NULL, &keypairs[0], NULL) == 0);
CHECK(ecount == 4);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, NULL, NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, NULL, NULL) == 0);
CHECK(ecount == 5);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &invalid_keypair, NULL, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &invalid_keypair, NULL) == 0);
CHECK(ecount == 6);
ecount = 0;
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &keypairs[0], NULL, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &keypairs[0], NULL) == 1);
CHECK(secp256k1_schnorrsig_verify(none, sig, msg, &pk[0]) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_schnorrsig_verify(sign, sig, msg, &pk[0]) == 0);
@ -201,7 +201,7 @@ void test_schnorrsig_bip_vectors_check_signing(const unsigned char *sk, const un
secp256k1_xonly_pubkey pk, pk_expected;
CHECK(secp256k1_keypair_create(ctx, &keypair, sk));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL, aux_rand));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, aux_rand));
CHECK(secp256k1_memcmp_var(sig, expected_sig, 64) == 0);
CHECK(secp256k1_xonly_pubkey_parse(ctx, &pk_expected, pk_serialized));
@ -685,16 +685,16 @@ void test_schnorrsig_sign(void) {
secp256k1_testrand256(sk);
CHECK(secp256k1_keypair_create(ctx, &keypair, sk));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL) == 1);
/* Test different nonce functions */
memset(sig, 1, sizeof(sig));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, nonce_function_failing, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_failing, NULL) == 0);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) == 0);
memset(&sig, 1, sizeof(sig));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, nonce_function_0, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_0, NULL) == 0);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) == 0);
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, nonce_function_overflowing, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_overflowing, NULL) == 1);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) != 0);
}
@ -717,7 +717,7 @@ void test_schnorrsig_sign_verify(void) {
for (i = 0; i < N_SIGS; i++) {
secp256k1_testrand256(msg[i]);
CHECK(secp256k1_schnorrsig_sign(ctx, sig[i], msg[i], &keypair, NULL, NULL));
CHECK(secp256k1_schnorrsig_sign(ctx, sig[i], msg[i], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[i], msg[i], &pk));
}
@ -746,13 +746,13 @@ void test_schnorrsig_sign_verify(void) {
}
/* Test overflowing s */
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL, NULL));
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
memset(&sig[0][32], 0xFF, 32);
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
/* Test negative s */
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL, NULL));
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
secp256k1_scalar_set_b32(&s, &sig[0][32], NULL);
secp256k1_scalar_negate(&s, &s);
@ -785,7 +785,7 @@ void test_schnorrsig_taproot(void) {
/* Key spend */
secp256k1_testrand256(msg);
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL) == 1);
/* Verify key spend */
CHECK(secp256k1_xonly_pubkey_parse(ctx, &output_pk, output_pk_bytes) == 1);
CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, &output_pk) == 1);

2
src/valgrind_ctime_test.c
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@ -166,7 +166,7 @@ void run_tests(secp256k1_context *ctx, unsigned char *key) {
ret = secp256k1_keypair_create(ctx, &keypair, key);
VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
CHECK(ret == 1);
ret = secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL, NULL);
ret = secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL);
VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
CHECK(ret == 1);
#endif