/*********************************************************************** * 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.* **********************************************************************/ #if defined HAVE_CONFIG_H #include "libsecp256k1-config.h" #endif #include #include #include #undef USE_ECMULT_STATIC_PRECOMPUTATION #ifndef EXHAUSTIVE_TEST_ORDER /* see group_impl.h for allowable values */ #define EXHAUSTIVE_TEST_ORDER 13 #define EXHAUSTIVE_TEST_LAMBDA 9 /* cube root of 1 mod 13 */ #endif #include "include/secp256k1.h" #include "group.h" #include "secp256k1.c" #include "testrand_impl.h" #ifdef ENABLE_MODULE_RECOVERY #include "src/modules/recovery/main_impl.h" #include "include/secp256k1_recovery.h" #endif /** stolen from tests.c */ void ge_equals_ge(const secp256k1_ge *a, const secp256k1_ge *b) { CHECK(a->infinity == b->infinity); if (a->infinity) { return; } CHECK(secp256k1_fe_equal_var(&a->x, &b->x)); CHECK(secp256k1_fe_equal_var(&a->y, &b->y)); } void ge_equals_gej(const secp256k1_ge *a, const secp256k1_gej *b) { secp256k1_fe z2s; secp256k1_fe u1, u2, s1, s2; CHECK(a->infinity == b->infinity); if (a->infinity) { return; } /* Check a.x * b.z^2 == b.x && a.y * b.z^3 == b.y, to avoid inverses. */ secp256k1_fe_sqr(&z2s, &b->z); secp256k1_fe_mul(&u1, &a->x, &z2s); u2 = b->x; secp256k1_fe_normalize_weak(&u2); secp256k1_fe_mul(&s1, &a->y, &z2s); secp256k1_fe_mul(&s1, &s1, &b->z); s2 = b->y; secp256k1_fe_normalize_weak(&s2); CHECK(secp256k1_fe_equal_var(&u1, &u2)); CHECK(secp256k1_fe_equal_var(&s1, &s2)); } void random_fe(secp256k1_fe *x) { unsigned char bin[32]; do { secp256k1_rand256(bin); if (secp256k1_fe_set_b32(x, bin)) { return; } } while(1); } /** END stolen from tests.c */ int secp256k1_nonce_function_smallint(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int attempt) { secp256k1_scalar s; int *idata = data; (void)msg32; (void)key32; (void)algo16; /* Some nonces cannot be used because they'd cause s and/or r to be zero. * The signing function has retry logic here that just re-calls the nonce * function with an increased `attempt`. So if attempt > 0 this means we * need to change the nonce to avoid an infinite loop. */ if (attempt > 0) { *idata = (*idata + 1) % EXHAUSTIVE_TEST_ORDER; } secp256k1_scalar_set_int(&s, *idata); secp256k1_scalar_get_b32(nonce32, &s); return 1; } #ifdef USE_ENDOMORPHISM void test_exhaustive_endomorphism(const secp256k1_ge *group, int order) { int i; for (i = 0; i < order; i++) { secp256k1_ge res; secp256k1_ge_mul_lambda(&res, &group[i]); ge_equals_ge(&group[i * EXHAUSTIVE_TEST_LAMBDA % EXHAUSTIVE_TEST_ORDER], &res); } } #endif void test_exhaustive_addition(const secp256k1_ge *group, const secp256k1_gej *groupj, int order) { int i, j; /* Sanity-check (and check infinity functions) */ CHECK(secp256k1_ge_is_infinity(&group[0])); CHECK(secp256k1_gej_is_infinity(&groupj[0])); for (i = 1; i < order; i++) { CHECK(!secp256k1_ge_is_infinity(&group[i])); CHECK(!secp256k1_gej_is_infinity(&groupj[i])); } /* Check all addition formulae */ for (j = 0; j < order; j++) { secp256k1_fe fe_inv; secp256k1_fe_inv(&fe_inv, &groupj[j].z); for (i = 0; i < order; i++) { secp256k1_ge zless_gej; secp256k1_gej tmp; /* add_var */ secp256k1_gej_add_var(&tmp, &groupj[i], &groupj[j], NULL); ge_equals_gej(&group[(i + j) % order], &tmp); /* add_ge */ if (j > 0) { secp256k1_gej_add_ge(&tmp, &groupj[i], &group[j]); ge_equals_gej(&group[(i + j) % order], &tmp); } /* add_ge_var */ secp256k1_gej_add_ge_var(&tmp, &groupj[i], &group[j], NULL); ge_equals_gej(&group[(i + j) % order], &tmp); /* add_zinv_var */ zless_gej.infinity = groupj[j].infinity; zless_gej.x = groupj[j].x; zless_gej.y = groupj[j].y; secp256k1_gej_add_zinv_var(&tmp, &groupj[i], &zless_gej, &fe_inv); ge_equals_gej(&group[(i + j) % order], &tmp); } } /* Check doubling */ for (i = 0; i < order; i++) { secp256k1_gej tmp; if (i > 0) { secp256k1_gej_double_nonzero(&tmp, &groupj[i], NULL); ge_equals_gej(&group[(2 * i) % order], &tmp); } secp256k1_gej_double_var(&tmp, &groupj[i], NULL); ge_equals_gej(&group[(2 * i) % order], &tmp); } /* Check negation */ for (i = 1; i < order; i++) { secp256k1_ge tmp; secp256k1_gej tmpj; secp256k1_ge_neg(&tmp, &group[i]); ge_equals_ge(&group[order - i], &tmp); secp256k1_gej_neg(&tmpj, &groupj[i]); ge_equals_gej(&group[order - i], &tmpj); } } void test_exhaustive_ecmult(const secp256k1_context *ctx, const secp256k1_ge *group, const secp256k1_gej *groupj, int order) { int i, j, r_log; for (r_log = 1; r_log < order; r_log++) { for (j = 0; j < order; j++) { for (i = 0; i < order; i++) { secp256k1_gej tmp; secp256k1_scalar na, ng; secp256k1_scalar_set_int(&na, i); secp256k1_scalar_set_int(&ng, j); secp256k1_ecmult(&ctx->ecmult_ctx, &tmp, &groupj[r_log], &na, &ng); ge_equals_gej(&group[(i * r_log + j) % order], &tmp); if (i > 0) { secp256k1_ecmult_const(&tmp, &group[i], &ng); ge_equals_gej(&group[(i * j) % order], &tmp); } } } } } void r_from_k(secp256k1_scalar *r, const secp256k1_ge *group, int k) { secp256k1_fe x; unsigned char x_bin[32]; k %= EXHAUSTIVE_TEST_ORDER; x = group[k].x; secp256k1_fe_normalize(&x); secp256k1_fe_get_b32(x_bin, &x); secp256k1_scalar_set_b32(r, x_bin, NULL); } void test_exhaustive_verify(const secp256k1_context *ctx, const secp256k1_ge *group, int order) { int s, r, msg, key; for (s = 1; s < order; s++) { for (r = 1; r < order; r++) { for (msg = 1; msg < order; msg++) { for (key = 1; key < order; key++) { secp256k1_ge nonconst_ge; secp256k1_ecdsa_signature sig; secp256k1_pubkey pk; secp256k1_scalar sk_s, msg_s, r_s, s_s; secp256k1_scalar s_times_k_s, msg_plus_r_times_sk_s; int k, should_verify; unsigned char msg32[32]; secp256k1_scalar_set_int(&s_s, s); secp256k1_scalar_set_int(&r_s, r); secp256k1_scalar_set_int(&msg_s, msg); secp256k1_scalar_set_int(&sk_s, key); /* Verify by hand */ /* Run through every k value that gives us this r and check that *one* works. * Note there could be none, there could be multiple, ECDSA is weird. */ should_verify = 0; for (k = 0; k < order; k++) { secp256k1_scalar check_x_s; r_from_k(&check_x_s, group, k); if (r_s == check_x_s) { secp256k1_scalar_set_int(&s_times_k_s, k); secp256k1_scalar_mul(&s_times_k_s, &s_times_k_s, &s_s); secp256k1_scalar_mul(&msg_plus_r_times_sk_s, &r_s, &sk_s); secp256k1_scalar_add(&msg_plus_r_times_sk_s, &msg_plus_r_times_sk_s, &msg_s); should_verify |= secp256k1_scalar_eq(&s_times_k_s, &msg_plus_r_times_sk_s); } } /* nb we have a "high s" rule */ should_verify &= !secp256k1_scalar_is_high(&s_s); /* Verify by calling verify */ secp256k1_ecdsa_signature_save(&sig, &r_s, &s_s); memcpy(&nonconst_ge, &group[sk_s], sizeof(nonconst_ge)); secp256k1_pubkey_save(&pk, &nonconst_ge); secp256k1_scalar_get_b32(msg32, &msg_s); CHECK(should_verify == secp256k1_ecdsa_verify(ctx, &sig, msg32, &pk)); } } } } } void test_exhaustive_sign(const secp256k1_context *ctx, const secp256k1_ge *group, int order) { int i, j, k; /* Loop */ for (i = 1; i < order; i++) { /* message */ for (j = 1; j < order; j++) { /* key */ for (k = 1; k < order; k++) { /* nonce */ const int starting_k = k; secp256k1_ecdsa_signature sig; secp256k1_scalar sk, msg, r, s, expected_r; unsigned char sk32[32], msg32[32]; secp256k1_scalar_set_int(&msg, i); secp256k1_scalar_set_int(&sk, j); secp256k1_scalar_get_b32(sk32, &sk); secp256k1_scalar_get_b32(msg32, &msg); secp256k1_ecdsa_sign(ctx, &sig, msg32, sk32, secp256k1_nonce_function_smallint, &k); secp256k1_ecdsa_signature_load(ctx, &r, &s, &sig); /* Note that we compute expected_r *after* signing -- this is important * because our nonce-computing function function might change k during * signing. */ r_from_k(&expected_r, group, k); CHECK(r == expected_r); CHECK((k * s) % order == (i + r * j) % order || (k * (EXHAUSTIVE_TEST_ORDER - s)) % order == (i + r * j) % order); /* Overflow means we've tried every possible nonce */ if (k < starting_k) { break; } } } } /* We would like to verify zero-knowledge here by counting how often every * possible (s, r) tuple appears, but because the group order is larger * than the field order, when coercing the x-values to scalar values, some * appear more often than others, so we are actually not zero-knowledge. * (This effect also appears in the real code, but the difference is on the * order of 1/2^128th the field order, so the deviation is not useful to a * computationally bounded attacker.) */ } #ifdef ENABLE_MODULE_RECOVERY void test_exhaustive_recovery_sign(const secp256k1_context *ctx, const secp256k1_ge *group, int order) { int i, j, k; /* Loop */ for (i = 1; i < order; i++) { /* message */ for (j = 1; j < order; j++) { /* key */ for (k = 1; k < order; k++) { /* nonce */ const int starting_k = k; secp256k1_fe r_dot_y_normalized; secp256k1_ecdsa_recoverable_signature rsig; secp256k1_ecdsa_signature sig; secp256k1_scalar sk, msg, r, s, expected_r; unsigned char sk32[32], msg32[32]; int expected_recid; int recid; secp256k1_scalar_set_int(&msg, i); secp256k1_scalar_set_int(&sk, j); secp256k1_scalar_get_b32(sk32, &sk); secp256k1_scalar_get_b32(msg32, &msg); secp256k1_ecdsa_sign_recoverable(ctx, &rsig, msg32, sk32, secp256k1_nonce_function_smallint, &k); /* Check directly */ secp256k1_ecdsa_recoverable_signature_load(ctx, &r, &s, &recid, &rsig); r_from_k(&expected_r, group, k); CHECK(r == expected_r); CHECK((k * s) % order == (i + r * j) % order || (k * (EXHAUSTIVE_TEST_ORDER - s)) % order == (i + r * j) % order); /* In computing the recid, there is an overflow condition that is disabled in * scalar_low_impl.h `secp256k1_scalar_set_b32` because almost every r.y value * will exceed the group order, and our signing code always holds out for r * values that don't overflow, so with a proper overflow check the tests would * loop indefinitely. */ r_dot_y_normalized = group[k].y; secp256k1_fe_normalize(&r_dot_y_normalized); /* Also the recovery id is flipped depending if we hit the low-s branch */ if ((k * s) % order == (i + r * j) % order) { expected_recid = secp256k1_fe_is_odd(&r_dot_y_normalized) ? 1 : 0; } else { expected_recid = secp256k1_fe_is_odd(&r_dot_y_normalized) ? 0 : 1; } CHECK(recid == expected_recid); /* Convert to a standard sig then check */ secp256k1_ecdsa_recoverable_signature_convert(ctx, &sig, &rsig); secp256k1_ecdsa_signature_load(ctx, &r, &s, &sig); /* Note that we compute expected_r *after* signing -- this is important * because our nonce-computing function function might change k during * signing. */ r_from_k(&expected_r, group, k); CHECK(r == expected_r); CHECK((k * s) % order == (i + r * j) % order || (k * (EXHAUSTIVE_TEST_ORDER - s)) % order == (i + r * j) % order); /* Overflow means we've tried every possible nonce */ if (k < starting_k) { break; } } } } } void test_exhaustive_recovery_verify(const secp256k1_context *ctx, const secp256k1_ge *group, int order) { /* This is essentially a copy of test_exhaustive_verify, with recovery added */ int s, r, msg, key; for (s = 1; s < order; s++) { for (r = 1; r < order; r++) { for (msg = 1; msg < order; msg++) { for (key = 1; key < order; key++) { secp256k1_ge nonconst_ge; secp256k1_ecdsa_recoverable_signature rsig; secp256k1_ecdsa_signature sig; secp256k1_pubkey pk; secp256k1_scalar sk_s, msg_s, r_s, s_s; secp256k1_scalar s_times_k_s, msg_plus_r_times_sk_s; int recid = 0; int k, should_verify; unsigned char msg32[32]; secp256k1_scalar_set_int(&s_s, s); secp256k1_scalar_set_int(&r_s, r); secp256k1_scalar_set_int(&msg_s, msg); secp256k1_scalar_set_int(&sk_s, key); secp256k1_scalar_get_b32(msg32, &msg_s); /* Verify by hand */ /* Run through every k value that gives us this r and check that *one* works. * Note there could be none, there could be multiple, ECDSA is weird. */ should_verify = 0; for (k = 0; k < order; k++) { secp256k1_scalar check_x_s; r_from_k(&check_x_s, group, k); if (r_s == check_x_s) { secp256k1_scalar_set_int(&s_times_k_s, k); secp256k1_scalar_mul(&s_times_k_s, &s_times_k_s, &s_s); secp256k1_scalar_mul(&msg_plus_r_times_sk_s, &r_s, &sk_s); secp256k1_scalar_add(&msg_plus_r_times_sk_s, &msg_plus_r_times_sk_s, &msg_s); should_verify |= secp256k1_scalar_eq(&s_times_k_s, &msg_plus_r_times_sk_s); } } /* nb we have a "high s" rule */ should_verify &= !secp256k1_scalar_is_high(&s_s); /* We would like to try recovering the pubkey and checking that it matches, * but pubkey recovery is impossible in the exhaustive tests (the reason * being that there are 12 nonzero r values, 12 nonzero points, and no * overlap between the sets, so there are no valid signatures). */ /* Verify by converting to a standard signature and calling verify */ secp256k1_ecdsa_recoverable_signature_save(&rsig, &r_s, &s_s, recid); secp256k1_ecdsa_recoverable_signature_convert(ctx, &sig, &rsig); memcpy(&nonconst_ge, &group[sk_s], sizeof(nonconst_ge)); secp256k1_pubkey_save(&pk, &nonconst_ge); CHECK(should_verify == secp256k1_ecdsa_verify(ctx, &sig, msg32, &pk)); } } } } } #endif int main(void) { int i; secp256k1_gej groupj[EXHAUSTIVE_TEST_ORDER]; secp256k1_ge group[EXHAUSTIVE_TEST_ORDER]; /* Build context */ secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); /* TODO set z = 1, then do num_tests runs with random z values */ /* Generate the entire group */ secp256k1_gej_set_infinity(&groupj[0]); secp256k1_ge_set_gej(&group[0], &groupj[0]); for (i = 1; i < EXHAUSTIVE_TEST_ORDER; i++) { /* Set a different random z-value for each Jacobian point */ secp256k1_fe z; random_fe(&z); secp256k1_gej_add_ge(&groupj[i], &groupj[i - 1], &secp256k1_ge_const_g); secp256k1_ge_set_gej(&group[i], &groupj[i]); secp256k1_gej_rescale(&groupj[i], &z); /* Verify against ecmult_gen */ { secp256k1_scalar scalar_i; secp256k1_gej generatedj; secp256k1_ge generated; secp256k1_scalar_set_int(&scalar_i, i); secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &generatedj, &scalar_i); secp256k1_ge_set_gej(&generated, &generatedj); CHECK(group[i].infinity == 0); CHECK(generated.infinity == 0); CHECK(secp256k1_fe_equal_var(&generated.x, &group[i].x)); CHECK(secp256k1_fe_equal_var(&generated.y, &group[i].y)); } } /* Run the tests */ #ifdef USE_ENDOMORPHISM test_exhaustive_endomorphism(group, EXHAUSTIVE_TEST_ORDER); #endif test_exhaustive_addition(group, groupj, EXHAUSTIVE_TEST_ORDER); test_exhaustive_ecmult(ctx, group, groupj, EXHAUSTIVE_TEST_ORDER); test_exhaustive_sign(ctx, group, EXHAUSTIVE_TEST_ORDER); test_exhaustive_verify(ctx, group, EXHAUSTIVE_TEST_ORDER); #ifdef ENABLE_MODULE_RECOVERY test_exhaustive_recovery_sign(ctx, group, EXHAUSTIVE_TEST_ORDER); test_exhaustive_recovery_verify(ctx, group, EXHAUSTIVE_TEST_ORDER); #endif secp256k1_context_destroy(ctx); return 0; }