From aa404d53bef21d252a23171381d4bfda6e7e25c6 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Sun, 11 Oct 2020 15:30:37 -0700 Subject: [PATCH] Move secp256k1_scalar_{inverse{_var},is_even} to per-impl files This temporarily duplicates the inversion code across the 4x64 and 8x32 implementations. Those implementations will be replaced in a later commit. --- src/scalar_4x64_impl.h | 179 ++++++++++++++++++++++++++++++++++++++ src/scalar_8x32_impl.h | 179 ++++++++++++++++++++++++++++++++++++++ src/scalar_impl.h | 191 ----------------------------------------- src/scalar_low_impl.h | 15 ++++ 4 files changed, 373 insertions(+), 191 deletions(-) diff --git a/src/scalar_4x64_impl.h b/src/scalar_4x64_impl.h index 3eaa0418c6237..6ba38e25e7348 100644 --- a/src/scalar_4x64_impl.h +++ b/src/scalar_4x64_impl.h @@ -955,4 +955,183 @@ static SECP256K1_INLINE void secp256k1_scalar_cmov(secp256k1_scalar *r, const se r->d[3] = (r->d[3] & mask0) | (a->d[3] & mask1); } +static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *x) { + secp256k1_scalar *t; + int i; + /* First compute xN as x ^ (2^N - 1) for some values of N, + * and uM as x ^ M for some values of M. */ + secp256k1_scalar x2, x3, x6, x8, x14, x28, x56, x112, x126; + secp256k1_scalar u2, u5, u9, u11, u13; + + secp256k1_scalar_sqr(&u2, x); + secp256k1_scalar_mul(&x2, &u2, x); + secp256k1_scalar_mul(&u5, &u2, &x2); + secp256k1_scalar_mul(&x3, &u5, &u2); + secp256k1_scalar_mul(&u9, &x3, &u2); + secp256k1_scalar_mul(&u11, &u9, &u2); + secp256k1_scalar_mul(&u13, &u11, &u2); + + secp256k1_scalar_sqr(&x6, &u13); + secp256k1_scalar_sqr(&x6, &x6); + secp256k1_scalar_mul(&x6, &x6, &u11); + + secp256k1_scalar_sqr(&x8, &x6); + secp256k1_scalar_sqr(&x8, &x8); + secp256k1_scalar_mul(&x8, &x8, &x2); + + secp256k1_scalar_sqr(&x14, &x8); + for (i = 0; i < 5; i++) { + secp256k1_scalar_sqr(&x14, &x14); + } + secp256k1_scalar_mul(&x14, &x14, &x6); + + secp256k1_scalar_sqr(&x28, &x14); + for (i = 0; i < 13; i++) { + secp256k1_scalar_sqr(&x28, &x28); + } + secp256k1_scalar_mul(&x28, &x28, &x14); + + secp256k1_scalar_sqr(&x56, &x28); + for (i = 0; i < 27; i++) { + secp256k1_scalar_sqr(&x56, &x56); + } + secp256k1_scalar_mul(&x56, &x56, &x28); + + secp256k1_scalar_sqr(&x112, &x56); + for (i = 0; i < 55; i++) { + secp256k1_scalar_sqr(&x112, &x112); + } + secp256k1_scalar_mul(&x112, &x112, &x56); + + secp256k1_scalar_sqr(&x126, &x112); + for (i = 0; i < 13; i++) { + secp256k1_scalar_sqr(&x126, &x126); + } + secp256k1_scalar_mul(&x126, &x126, &x14); + + /* Then accumulate the final result (t starts at x126). */ + t = &x126; + for (i = 0; i < 3; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 5; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 3; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 10; i++) { /* 0000000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 9; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x8); /* 11111111 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 5; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x2); /* 11 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 10; i++) { /* 000000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 00000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, x); /* 1 */ + for (i = 0; i < 8; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(r, t, &x6); /* 111111 */ +} + +static void secp256k1_scalar_inverse_var(secp256k1_scalar *r, const secp256k1_scalar *x) { +#if defined(USE_SCALAR_INV_BUILTIN) + secp256k1_scalar_inverse(r, x); +#elif defined(USE_SCALAR_INV_NUM) + unsigned char b[32]; + secp256k1_num n, m; + secp256k1_scalar t = *x; + secp256k1_scalar_get_b32(b, &t); + secp256k1_num_set_bin(&n, b, 32); + secp256k1_scalar_order_get_num(&m); + secp256k1_num_mod_inverse(&n, &n, &m); + secp256k1_num_get_bin(b, 32, &n); + secp256k1_scalar_set_b32(r, b, NULL); + /* Verify that the inverse was computed correctly, without GMP code. */ + secp256k1_scalar_mul(&t, &t, r); + CHECK(secp256k1_scalar_is_one(&t)); +#else +#error "Please select scalar inverse implementation" +#endif +} + +SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a) { + return !(a->d[0] & 1); +} + #endif /* SECP256K1_SCALAR_REPR_IMPL_H */ diff --git a/src/scalar_8x32_impl.h b/src/scalar_8x32_impl.h index bf98e01d76284..53b8d4ec4b060 100644 --- a/src/scalar_8x32_impl.h +++ b/src/scalar_8x32_impl.h @@ -731,4 +731,183 @@ static SECP256K1_INLINE void secp256k1_scalar_cmov(secp256k1_scalar *r, const se r->d[7] = (r->d[7] & mask0) | (a->d[7] & mask1); } +static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *x) { + secp256k1_scalar *t; + int i; + /* First compute xN as x ^ (2^N - 1) for some values of N, + * and uM as x ^ M for some values of M. */ + secp256k1_scalar x2, x3, x6, x8, x14, x28, x56, x112, x126; + secp256k1_scalar u2, u5, u9, u11, u13; + + secp256k1_scalar_sqr(&u2, x); + secp256k1_scalar_mul(&x2, &u2, x); + secp256k1_scalar_mul(&u5, &u2, &x2); + secp256k1_scalar_mul(&x3, &u5, &u2); + secp256k1_scalar_mul(&u9, &x3, &u2); + secp256k1_scalar_mul(&u11, &u9, &u2); + secp256k1_scalar_mul(&u13, &u11, &u2); + + secp256k1_scalar_sqr(&x6, &u13); + secp256k1_scalar_sqr(&x6, &x6); + secp256k1_scalar_mul(&x6, &x6, &u11); + + secp256k1_scalar_sqr(&x8, &x6); + secp256k1_scalar_sqr(&x8, &x8); + secp256k1_scalar_mul(&x8, &x8, &x2); + + secp256k1_scalar_sqr(&x14, &x8); + for (i = 0; i < 5; i++) { + secp256k1_scalar_sqr(&x14, &x14); + } + secp256k1_scalar_mul(&x14, &x14, &x6); + + secp256k1_scalar_sqr(&x28, &x14); + for (i = 0; i < 13; i++) { + secp256k1_scalar_sqr(&x28, &x28); + } + secp256k1_scalar_mul(&x28, &x28, &x14); + + secp256k1_scalar_sqr(&x56, &x28); + for (i = 0; i < 27; i++) { + secp256k1_scalar_sqr(&x56, &x56); + } + secp256k1_scalar_mul(&x56, &x56, &x28); + + secp256k1_scalar_sqr(&x112, &x56); + for (i = 0; i < 55; i++) { + secp256k1_scalar_sqr(&x112, &x112); + } + secp256k1_scalar_mul(&x112, &x112, &x56); + + secp256k1_scalar_sqr(&x126, &x112); + for (i = 0; i < 13; i++) { + secp256k1_scalar_sqr(&x126, &x126); + } + secp256k1_scalar_mul(&x126, &x126, &x14); + + /* Then accumulate the final result (t starts at x126). */ + t = &x126; + for (i = 0; i < 3; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 5; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 3; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u5); /* 101 */ + for (i = 0; i < 10; i++) { /* 0000000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 4; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x3); /* 111 */ + for (i = 0; i < 9; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x8); /* 11111111 */ + for (i = 0; i < 5; i++) { /* 0 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u11); /* 1011 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 5; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &x2); /* 11 */ + for (i = 0; i < 6; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 10; i++) { /* 000000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u13); /* 1101 */ + for (i = 0; i < 4; i++) { + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, &u9); /* 1001 */ + for (i = 0; i < 6; i++) { /* 00000 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(t, t, x); /* 1 */ + for (i = 0; i < 8; i++) { /* 00 */ + secp256k1_scalar_sqr(t, t); + } + secp256k1_scalar_mul(r, t, &x6); /* 111111 */ +} + +static void secp256k1_scalar_inverse_var(secp256k1_scalar *r, const secp256k1_scalar *x) { +#if defined(USE_SCALAR_INV_BUILTIN) + secp256k1_scalar_inverse(r, x); +#elif defined(USE_SCALAR_INV_NUM) + unsigned char b[32]; + secp256k1_num n, m; + secp256k1_scalar t = *x; + secp256k1_scalar_get_b32(b, &t); + secp256k1_num_set_bin(&n, b, 32); + secp256k1_scalar_order_get_num(&m); + secp256k1_num_mod_inverse(&n, &n, &m); + secp256k1_num_get_bin(b, 32, &n); + secp256k1_scalar_set_b32(r, b, NULL); + /* Verify that the inverse was computed correctly, without GMP code. */ + secp256k1_scalar_mul(&t, &t, r); + CHECK(secp256k1_scalar_is_one(&t)); +#else +#error "Please select scalar inverse implementation" +#endif +} + +SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a) { + return !(a->d[0] & 1); +} + #endif /* SECP256K1_SCALAR_REPR_IMPL_H */ diff --git a/src/scalar_impl.h b/src/scalar_impl.h index 61c1fbd58e28c..b328afdb9b937 100644 --- a/src/scalar_impl.h +++ b/src/scalar_impl.h @@ -65,197 +65,6 @@ static int secp256k1_scalar_set_b32_seckey(secp256k1_scalar *r, const unsigned c return (!overflow) & (!secp256k1_scalar_is_zero(r)); } -static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *x) { -#if defined(EXHAUSTIVE_TEST_ORDER) - int i; - *r = 0; - for (i = 0; i < EXHAUSTIVE_TEST_ORDER; i++) - if ((i * *x) % EXHAUSTIVE_TEST_ORDER == 1) - *r = i; - /* If this VERIFY_CHECK triggers we were given a noninvertible scalar (and thus - * have a composite group order; fix it in exhaustive_tests.c). */ - VERIFY_CHECK(*r != 0); -} -#else - secp256k1_scalar *t; - int i; - /* First compute xN as x ^ (2^N - 1) for some values of N, - * and uM as x ^ M for some values of M. */ - secp256k1_scalar x2, x3, x6, x8, x14, x28, x56, x112, x126; - secp256k1_scalar u2, u5, u9, u11, u13; - - secp256k1_scalar_sqr(&u2, x); - secp256k1_scalar_mul(&x2, &u2, x); - secp256k1_scalar_mul(&u5, &u2, &x2); - secp256k1_scalar_mul(&x3, &u5, &u2); - secp256k1_scalar_mul(&u9, &x3, &u2); - secp256k1_scalar_mul(&u11, &u9, &u2); - secp256k1_scalar_mul(&u13, &u11, &u2); - - secp256k1_scalar_sqr(&x6, &u13); - secp256k1_scalar_sqr(&x6, &x6); - secp256k1_scalar_mul(&x6, &x6, &u11); - - secp256k1_scalar_sqr(&x8, &x6); - secp256k1_scalar_sqr(&x8, &x8); - secp256k1_scalar_mul(&x8, &x8, &x2); - - secp256k1_scalar_sqr(&x14, &x8); - for (i = 0; i < 5; i++) { - secp256k1_scalar_sqr(&x14, &x14); - } - secp256k1_scalar_mul(&x14, &x14, &x6); - - secp256k1_scalar_sqr(&x28, &x14); - for (i = 0; i < 13; i++) { - secp256k1_scalar_sqr(&x28, &x28); - } - secp256k1_scalar_mul(&x28, &x28, &x14); - - secp256k1_scalar_sqr(&x56, &x28); - for (i = 0; i < 27; i++) { - secp256k1_scalar_sqr(&x56, &x56); - } - secp256k1_scalar_mul(&x56, &x56, &x28); - - secp256k1_scalar_sqr(&x112, &x56); - for (i = 0; i < 55; i++) { - secp256k1_scalar_sqr(&x112, &x112); - } - secp256k1_scalar_mul(&x112, &x112, &x56); - - secp256k1_scalar_sqr(&x126, &x112); - for (i = 0; i < 13; i++) { - secp256k1_scalar_sqr(&x126, &x126); - } - secp256k1_scalar_mul(&x126, &x126, &x14); - - /* Then accumulate the final result (t starts at x126). */ - t = &x126; - for (i = 0; i < 3; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u5); /* 101 */ - for (i = 0; i < 4; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 4; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u5); /* 101 */ - for (i = 0; i < 5; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u11); /* 1011 */ - for (i = 0; i < 4; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u11); /* 1011 */ - for (i = 0; i < 4; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 5; i++) { /* 00 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 6; i++) { /* 00 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u13); /* 1101 */ - for (i = 0; i < 4; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u5); /* 101 */ - for (i = 0; i < 3; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 5; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u9); /* 1001 */ - for (i = 0; i < 6; i++) { /* 000 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u5); /* 101 */ - for (i = 0; i < 10; i++) { /* 0000000 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 4; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x3); /* 111 */ - for (i = 0; i < 9; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x8); /* 11111111 */ - for (i = 0; i < 5; i++) { /* 0 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u9); /* 1001 */ - for (i = 0; i < 6; i++) { /* 00 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u11); /* 1011 */ - for (i = 0; i < 4; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u13); /* 1101 */ - for (i = 0; i < 5; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &x2); /* 11 */ - for (i = 0; i < 6; i++) { /* 00 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u13); /* 1101 */ - for (i = 0; i < 10; i++) { /* 000000 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u13); /* 1101 */ - for (i = 0; i < 4; i++) { - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, &u9); /* 1001 */ - for (i = 0; i < 6; i++) { /* 00000 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(t, t, x); /* 1 */ - for (i = 0; i < 8; i++) { /* 00 */ - secp256k1_scalar_sqr(t, t); - } - secp256k1_scalar_mul(r, t, &x6); /* 111111 */ -} - -SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a) { - return !(a->d[0] & 1); -} -#endif - -static void secp256k1_scalar_inverse_var(secp256k1_scalar *r, const secp256k1_scalar *x) { -#if defined(USE_SCALAR_INV_BUILTIN) - secp256k1_scalar_inverse(r, x); -#elif defined(USE_SCALAR_INV_NUM) - unsigned char b[32]; - secp256k1_num n, m; - secp256k1_scalar t = *x; - secp256k1_scalar_get_b32(b, &t); - secp256k1_num_set_bin(&n, b, 32); - secp256k1_scalar_order_get_num(&m); - secp256k1_num_mod_inverse(&n, &n, &m); - secp256k1_num_get_bin(b, 32, &n); - secp256k1_scalar_set_b32(r, b, NULL); - /* Verify that the inverse was computed correctly, without GMP code. */ - secp256k1_scalar_mul(&t, &t, r); - CHECK(secp256k1_scalar_is_one(&t)); -#else -#error "Please select scalar inverse implementation" -#endif -} - /* These parameters are generated using sage/gen_exhaustive_groups.sage. */ #if defined(EXHAUSTIVE_TEST_ORDER) # if EXHAUSTIVE_TEST_ORDER == 13 diff --git a/src/scalar_low_impl.h b/src/scalar_low_impl.h index 98ffd1536eb2d..eff270720a80e 100644 --- a/src/scalar_low_impl.h +++ b/src/scalar_low_impl.h @@ -125,4 +125,19 @@ static SECP256K1_INLINE void secp256k1_scalar_cmov(secp256k1_scalar *r, const se *r = (*r & mask0) | (*a & mask1); } +static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *x) { + int i; + *r = 0; + for (i = 0; i < EXHAUSTIVE_TEST_ORDER; i++) + if ((i * *x) % EXHAUSTIVE_TEST_ORDER == 1) + *r = i; + /* If this VERIFY_CHECK triggers we were given a noninvertible scalar (and thus + * have a composite group order; fix it in exhaustive_tests.c). */ + VERIFY_CHECK(*r != 0); +} + +static void secp256k1_scalar_inverse_var(secp256k1_scalar *r, const secp256k1_scalar *x) { + secp256k1_scalar_inverse(r, x); +} + #endif /* SECP256K1_SCALAR_REPR_IMPL_H */