diff --git a/src/ecmult_impl.h b/src/ecmult_impl.h index 587c88f6a621e..73674db937363 100644 --- a/src/ecmult_impl.h +++ b/src/ecmult_impl.h @@ -214,7 +214,6 @@ struct secp256k1_strauss_point_state { int wnaf_na_lam[129]; int bits_na_1; int bits_na_lam; - size_t input_pos; }; struct secp256k1_strauss_state { @@ -238,12 +237,13 @@ static void secp256k1_ecmult_strauss_wnaf(const struct secp256k1_strauss_state * size_t np; size_t no = 0; + secp256k1_fe_set_int(&Z, 1); for (np = 0; np < num; ++np) { + secp256k1_gej tmp; secp256k1_scalar na_1, na_lam; if (secp256k1_scalar_is_zero(&na[np]) || secp256k1_gej_is_infinity(&a[np])) { continue; } - state->ps[no].input_pos = np; /* split na into na_1 and na_lam (where na = na_1 + na_lam*lambda, and na_1 and na_lam are ~128 bit) */ secp256k1_scalar_split_lambda(&na_1, &na_lam, &na[np]); @@ -258,37 +258,33 @@ static void secp256k1_ecmult_strauss_wnaf(const struct secp256k1_strauss_state * if (state->ps[no].bits_na_lam > bits) { bits = state->ps[no].bits_na_lam; } - ++no; - } - /* Calculate odd multiples of a. - * All multiples are brought to the same Z 'denominator', which is stored - * in Z. Due to secp256k1' isomorphism we can do all operations pretending - * that the Z coordinate was 1, use affine addition formulae, and correct - * the Z coordinate of the result once at the end. - * The exception is the precomputed G table points, which are actually - * affine. Compared to the base used for other points, they have a Z ratio - * of 1/Z, so we can use secp256k1_gej_add_zinv_var, which uses the same - * isomorphism to efficiently add with a known Z inverse. - */ - if (no > 0) { - /* Compute the odd multiples in Jacobian form. */ - secp256k1_ecmult_odd_multiples_table(ECMULT_TABLE_SIZE(WINDOW_A), state->pre_a, state->aux, &Z, &a[state->ps[0].input_pos]); - for (np = 1; np < no; ++np) { - secp256k1_gej tmp = a[state->ps[np].input_pos]; + /* Calculate odd multiples of a. + * All multiples are brought to the same Z 'denominator', which is stored + * in Z. Due to secp256k1' isomorphism we can do all operations pretending + * that the Z coordinate was 1, use affine addition formulae, and correct + * the Z coordinate of the result once at the end. + * The exception is the precomputed G table points, which are actually + * affine. Compared to the base used for other points, they have a Z ratio + * of 1/Z, so we can use secp256k1_gej_add_zinv_var, which uses the same + * isomorphism to efficiently add with a known Z inverse. + */ + tmp = a[np]; + if (no) { #ifdef VERIFY secp256k1_fe_normalize_var(&Z); #endif secp256k1_gej_rescale(&tmp, &Z); - secp256k1_ecmult_odd_multiples_table(ECMULT_TABLE_SIZE(WINDOW_A), state->pre_a + np * ECMULT_TABLE_SIZE(WINDOW_A), state->aux + np * ECMULT_TABLE_SIZE(WINDOW_A), &Z, &tmp); - secp256k1_fe_mul(state->aux + np * ECMULT_TABLE_SIZE(WINDOW_A), state->aux + np * ECMULT_TABLE_SIZE(WINDOW_A), &(a[state->ps[np].input_pos].z)); } - /* Bring them to the same Z denominator. */ - secp256k1_ge_table_set_globalz(ECMULT_TABLE_SIZE(WINDOW_A) * no, state->pre_a, state->aux); - } else { - secp256k1_fe_set_int(&Z, 1); + secp256k1_ecmult_odd_multiples_table(ECMULT_TABLE_SIZE(WINDOW_A), state->pre_a + no * ECMULT_TABLE_SIZE(WINDOW_A), state->aux + no * ECMULT_TABLE_SIZE(WINDOW_A), &Z, &tmp); + if (no) secp256k1_fe_mul(state->aux + no * ECMULT_TABLE_SIZE(WINDOW_A), state->aux + no * ECMULT_TABLE_SIZE(WINDOW_A), &(a[np].z)); + + ++no; } + /* Bring them to the same Z denominator. */ + secp256k1_ge_table_set_globalz(ECMULT_TABLE_SIZE(WINDOW_A) * no, state->pre_a, state->aux); + for (np = 0; np < no; ++np) { for (i = 0; i < ECMULT_TABLE_SIZE(WINDOW_A); i++) { secp256k1_fe_mul(&state->aux[np * ECMULT_TABLE_SIZE(WINDOW_A) + i], &state->pre_a[np * ECMULT_TABLE_SIZE(WINDOW_A) + i].x, &secp256k1_const_beta);