From a575339c0282ba49a4f46c9c660a4cc3b6bfc703 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Thu, 29 Dec 2022 14:48:36 -0500 Subject: [PATCH] Remove bits argument from secp256k1_wnaf_const (always 256) --- src/bench_ecmult.c | 2 +- src/ecmult_const.h | 5 +-- src/ecmult_const_impl.h | 61 +++++++++++++----------------------- src/modules/ecdh/main_impl.h | 2 +- src/tests.c | 30 +++++++++--------- src/tests_exhaustive.c | 6 ++-- 6 files changed, 43 insertions(+), 63 deletions(-) diff --git a/src/bench_ecmult.c b/src/bench_ecmult.c index 98fb798d82676..27d694a7033c3 100644 --- a/src/bench_ecmult.c +++ b/src/bench_ecmult.c @@ -113,7 +113,7 @@ static void bench_ecmult_const(void* arg, int iters) { int i; for (i = 0; i < iters; ++i) { - secp256k1_ecmult_const(&data->output[i], &data->pubkeys[(data->offset1+i) % POINTS], &data->scalars[(data->offset2+i) % POINTS], 256); + secp256k1_ecmult_const(&data->output[i], &data->pubkeys[(data->offset1+i) % POINTS], &data->scalars[(data->offset2+i) % POINTS]); } } diff --git a/src/ecmult_const.h b/src/ecmult_const.h index 417f328535c7d..9e065d555d7b9 100644 --- a/src/ecmult_const.h +++ b/src/ecmult_const.h @@ -12,11 +12,9 @@ /** * Multiply: R = q*A (in constant-time) - * Here `bits` should be set to the maximum bitlength of the _absolute value_ of `q`, plus - * one because we internally sometimes add 2 to the number during the WNAF conversion. * A must not be infinity. */ -static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *q, int bits); +static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *q); /** * Same as secp256k1_ecmult_const, but takes in an x coordinate of the base point @@ -35,7 +33,6 @@ static int secp256k1_ecmult_const_xonly( const secp256k1_fe *n, const secp256k1_fe *d, const secp256k1_scalar *q, - int bits, int known_on_curve ); diff --git a/src/ecmult_const_impl.h b/src/ecmult_const_impl.h index f23e0ec89dca9..f2b6f48285fc5 100644 --- a/src/ecmult_const_impl.h +++ b/src/ecmult_const_impl.h @@ -130,7 +130,7 @@ static int secp256k1_wnaf_const(int *wnaf, const secp256k1_scalar *scalar, int w return skew; } -static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *scalar, int size) { +static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *scalar) { secp256k1_ge pre_a[ECMULT_TABLE_SIZE(WINDOW_A)]; secp256k1_ge tmpa; secp256k1_fe Z; @@ -145,18 +145,10 @@ static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, cons int i; /* build wnaf representation for q. */ - int rsize = size; - if (size > 128) { - rsize = 128; - /* split q into q_1 and q_lam (where q = q_1 + q_lam*lambda, and q_1 and q_lam are ~128 bit) */ - secp256k1_scalar_split_lambda(&q_1, &q_lam, scalar); - skew_1 = secp256k1_wnaf_const(wnaf_1, &q_1, WINDOW_A - 1, 128); - skew_lam = secp256k1_wnaf_const(wnaf_lam, &q_lam, WINDOW_A - 1, 128); - } else - { - skew_1 = secp256k1_wnaf_const(wnaf_1, scalar, WINDOW_A - 1, size); - skew_lam = 0; - } + /* split q into q_1 and q_lam (where q = q_1 + q_lam*lambda, and q_1 and q_lam are ~128 bit) */ + secp256k1_scalar_split_lambda(&q_1, &q_lam, scalar); + skew_1 = secp256k1_wnaf_const(wnaf_1, &q_1, WINDOW_A - 1, 128); + skew_lam = secp256k1_wnaf_const(wnaf_lam, &q_lam, WINDOW_A - 1, 128); /* Calculate odd multiples of a. * All multiples are brought to the same Z 'denominator', which is stored @@ -170,28 +162,23 @@ static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, cons for (i = 0; i < ECMULT_TABLE_SIZE(WINDOW_A); i++) { secp256k1_fe_normalize_weak(&pre_a[i].y); } - if (size > 128) { - for (i = 0; i < ECMULT_TABLE_SIZE(WINDOW_A); i++) { - secp256k1_ge_mul_lambda(&pre_a_lam[i], &pre_a[i]); - } - + for (i = 0; i < ECMULT_TABLE_SIZE(WINDOW_A); i++) { + secp256k1_ge_mul_lambda(&pre_a_lam[i], &pre_a[i]); } /* first loop iteration (separated out so we can directly set r, rather * than having it start at infinity, get doubled several times, then have * its new value added to it) */ - i = wnaf_1[WNAF_SIZE_BITS(rsize, WINDOW_A - 1)]; + i = wnaf_1[WNAF_SIZE_BITS(128, WINDOW_A - 1)]; VERIFY_CHECK(i != 0); ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a, i, WINDOW_A); secp256k1_gej_set_ge(r, &tmpa); - if (size > 128) { - i = wnaf_lam[WNAF_SIZE_BITS(rsize, WINDOW_A - 1)]; - VERIFY_CHECK(i != 0); - ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a_lam, i, WINDOW_A); - secp256k1_gej_add_ge(r, r, &tmpa); - } + i = wnaf_lam[WNAF_SIZE_BITS(128, WINDOW_A - 1)]; + VERIFY_CHECK(i != 0); + ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a_lam, i, WINDOW_A); + secp256k1_gej_add_ge(r, r, &tmpa); /* remaining loop iterations */ - for (i = WNAF_SIZE_BITS(rsize, WINDOW_A - 1) - 1; i >= 0; i--) { + for (i = WNAF_SIZE_BITS(128, WINDOW_A - 1) - 1; i >= 0; i--) { int n; int j; for (j = 0; j < WINDOW_A - 1; ++j) { @@ -202,12 +189,10 @@ static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, cons ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a, n, WINDOW_A); VERIFY_CHECK(n != 0); secp256k1_gej_add_ge(r, r, &tmpa); - if (size > 128) { - n = wnaf_lam[i]; - ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a_lam, n, WINDOW_A); - VERIFY_CHECK(n != 0); - secp256k1_gej_add_ge(r, r, &tmpa); - } + n = wnaf_lam[i]; + ECMULT_CONST_TABLE_GET_GE(&tmpa, pre_a_lam, n, WINDOW_A); + VERIFY_CHECK(n != 0); + secp256k1_gej_add_ge(r, r, &tmpa); } { @@ -218,17 +203,15 @@ static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, cons secp256k1_gej_add_ge(&tmpj, r, &tmpa); secp256k1_gej_cmov(r, &tmpj, skew_1); - if (size > 128) { - secp256k1_ge_neg(&tmpa, &pre_a_lam[0]); - secp256k1_gej_add_ge(&tmpj, r, &tmpa); - secp256k1_gej_cmov(r, &tmpj, skew_lam); - } + secp256k1_ge_neg(&tmpa, &pre_a_lam[0]); + secp256k1_gej_add_ge(&tmpj, r, &tmpa); + secp256k1_gej_cmov(r, &tmpj, skew_lam); } secp256k1_fe_mul(&r->z, &r->z, &Z); } -static int secp256k1_ecmult_const_xonly(secp256k1_fe* r, const secp256k1_fe *n, const secp256k1_fe *d, const secp256k1_scalar *q, int bits, int known_on_curve) { +static int secp256k1_ecmult_const_xonly(secp256k1_fe* r, const secp256k1_fe *n, const secp256k1_fe *d, const secp256k1_scalar *q, int known_on_curve) { /* This algorithm is a generalization of Peter Dettman's technique for * avoiding the square root in a random-basepoint x-only multiplication @@ -346,7 +329,7 @@ static int secp256k1_ecmult_const_xonly(secp256k1_fe* r, const secp256k1_fe *n, #ifdef VERIFY VERIFY_CHECK(!secp256k1_scalar_is_zero(q)); #endif - secp256k1_ecmult_const(&rj, &p, q, bits); + secp256k1_ecmult_const(&rj, &p, q); #ifdef VERIFY VERIFY_CHECK(!secp256k1_gej_is_infinity(&rj)); #endif diff --git a/src/modules/ecdh/main_impl.h b/src/modules/ecdh/main_impl.h index 5408c9de70710..82b082a9f0867 100644 --- a/src/modules/ecdh/main_impl.h +++ b/src/modules/ecdh/main_impl.h @@ -50,7 +50,7 @@ int secp256k1_ecdh(const secp256k1_context* ctx, unsigned char *output, const se overflow |= secp256k1_scalar_is_zero(&s); secp256k1_scalar_cmov(&s, &secp256k1_scalar_one, overflow); - secp256k1_ecmult_const(&res, &pt, &s, 256); + secp256k1_ecmult_const(&res, &pt, &s); secp256k1_ge_set_gej(&pt, &res); /* Compute a hash of the point */ diff --git a/src/tests.c b/src/tests.c index 729b7f852ea2b..a9201b74b3c07 100644 --- a/src/tests.c +++ b/src/tests.c @@ -4338,9 +4338,9 @@ static void test_ecmult_target(const secp256k1_scalar* target, int mode) { secp256k1_ecmult(&p2j, &pj, &n2, &zero); secp256k1_ecmult(&ptj, &pj, target, &zero); } else { - secp256k1_ecmult_const(&p1j, &p, &n1, 256); - secp256k1_ecmult_const(&p2j, &p, &n2, 256); - secp256k1_ecmult_const(&ptj, &p, target, 256); + secp256k1_ecmult_const(&p1j, &p, &n1); + secp256k1_ecmult_const(&p2j, &p, &n2); + secp256k1_ecmult_const(&ptj, &p, target); } /* Add them all up: n1*P + n2*P + target*P = (n1+n2+target)*P = (n1+n1-n1-n2)*P = 0. */ @@ -4403,7 +4403,7 @@ static void ecmult_const_random_mult(void) { 0xb84e4e1b, 0xfb77e21f, 0x96baae2a, 0x63dec956 ); secp256k1_gej b; - secp256k1_ecmult_const(&b, &a, &xn, 256); + secp256k1_ecmult_const(&b, &a, &xn); CHECK(secp256k1_ge_is_valid_var(&a)); ge_equals_gej(&expected_b, &b); @@ -4419,12 +4419,12 @@ static void ecmult_const_commutativity(void) { random_scalar_order_test(&a); random_scalar_order_test(&b); - secp256k1_ecmult_const(&res1, &secp256k1_ge_const_g, &a, 256); - secp256k1_ecmult_const(&res2, &secp256k1_ge_const_g, &b, 256); + secp256k1_ecmult_const(&res1, &secp256k1_ge_const_g, &a); + secp256k1_ecmult_const(&res2, &secp256k1_ge_const_g, &b); secp256k1_ge_set_gej(&mid1, &res1); secp256k1_ge_set_gej(&mid2, &res2); - secp256k1_ecmult_const(&res1, &mid1, &b, 256); - secp256k1_ecmult_const(&res2, &mid2, &a, 256); + secp256k1_ecmult_const(&res1, &mid1, &b); + secp256k1_ecmult_const(&res2, &mid2, &a); secp256k1_ge_set_gej(&mid1, &res1); secp256k1_ge_set_gej(&mid2, &res2); ge_equals_ge(&mid1, &mid2); @@ -4440,13 +4440,13 @@ static void ecmult_const_mult_zero_one(void) { secp256k1_scalar_negate(&negone, &one); random_group_element_test(&point); - secp256k1_ecmult_const(&res1, &point, &zero, 3); + secp256k1_ecmult_const(&res1, &point, &zero); secp256k1_ge_set_gej(&res2, &res1); CHECK(secp256k1_ge_is_infinity(&res2)); - secp256k1_ecmult_const(&res1, &point, &one, 2); + secp256k1_ecmult_const(&res1, &point, &one); secp256k1_ge_set_gej(&res2, &res1); ge_equals_ge(&res2, &point); - secp256k1_ecmult_const(&res1, &point, &negone, 256); + secp256k1_ecmult_const(&res1, &point, &negone); secp256k1_gej_neg(&res1, &res1); secp256k1_ge_set_gej(&res2, &res1); ge_equals_ge(&res2, &point); @@ -4476,7 +4476,7 @@ static void ecmult_const_mult_xonly(void) { n = base.x; } /* Perform x-only multiplication. */ - res = secp256k1_ecmult_const_xonly(&resx, &n, (i & 1) ? &d : NULL, &q, 256, i & 2); + res = secp256k1_ecmult_const_xonly(&resx, &n, (i & 1) ? &d : NULL, &q, i & 2); CHECK(res); /* Perform normal multiplication. */ secp256k1_gej_set_ge(&basej, &base); @@ -4509,7 +4509,7 @@ static void ecmult_const_mult_xonly(void) { } else { n = x; } - res = secp256k1_ecmult_const_xonly(&r, &n, (i & 1) ? &d : NULL, &q, 256, 0); + res = secp256k1_ecmult_const_xonly(&r, &n, (i & 1) ? &d : NULL, &q, 0); CHECK(res == 0); } } @@ -4534,7 +4534,7 @@ static void ecmult_const_chain_multiply(void) { for (i = 0; i < 100; ++i) { secp256k1_ge tmp; secp256k1_ge_set_gej(&tmp, &point); - secp256k1_ecmult_const(&point, &tmp, &scalar, 256); + secp256k1_ecmult_const(&point, &tmp, &scalar); } secp256k1_ge_set_gej(&res, &point); ge_equals_gej(&res, &expected_point); @@ -5432,7 +5432,7 @@ static void test_ecmult_accumulate(secp256k1_sha256* acc, const secp256k1_scalar secp256k1_ecmult(&rj3, &infj, &zero, x); secp256k1_ecmult_multi_var(NULL, scratch, &rj4, x, NULL, NULL, 0); secp256k1_ecmult_multi_var(NULL, scratch, &rj5, &zero, test_ecmult_accumulate_cb, (void*)x, 1); - secp256k1_ecmult_const(&rj6, &secp256k1_ge_const_g, x, 256); + secp256k1_ecmult_const(&rj6, &secp256k1_ge_const_g, x); secp256k1_ge_set_gej_var(&r, &rj1); ge_equals_gej(&r, &rj2); ge_equals_gej(&r, &rj3); diff --git a/src/tests_exhaustive.c b/src/tests_exhaustive.c index 63b6ef03afa71..e7bd6c724aea4 100644 --- a/src/tests_exhaustive.c +++ b/src/tests_exhaustive.c @@ -203,19 +203,19 @@ static void test_exhaustive_ecmult(const secp256k1_ge *group, const secp256k1_ge secp256k1_scalar_set_int(&ng, j); /* Test secp256k1_ecmult_const. */ - secp256k1_ecmult_const(&tmp, &group[i], &ng, 256); + secp256k1_ecmult_const(&tmp, &group[i], &ng); ge_equals_gej(&group[(i * j) % EXHAUSTIVE_TEST_ORDER], &tmp); if (j != 0) { /* Test secp256k1_ecmult_const_xonly with all curve X coordinates, and xd=NULL. */ - ret = secp256k1_ecmult_const_xonly(&tmpf, &group[i].x, NULL, &ng, 256, 0); + ret = secp256k1_ecmult_const_xonly(&tmpf, &group[i].x, NULL, &ng, 0); CHECK(ret); CHECK(secp256k1_fe_equal_var(&tmpf, &group[(i * j) % EXHAUSTIVE_TEST_ORDER].x)); /* Test secp256k1_ecmult_const_xonly with all curve X coordinates, with random xd. */ random_fe_non_zero(&xd); secp256k1_fe_mul(&xn, &xd, &group[i].x); - ret = secp256k1_ecmult_const_xonly(&tmpf, &xn, &xd, &ng, 256, 0); + ret = secp256k1_ecmult_const_xonly(&tmpf, &xn, &xd, &ng, 0); CHECK(ret); CHECK(secp256k1_fe_equal_var(&tmpf, &group[(i * j) % EXHAUSTIVE_TEST_ORDER].x)); }