diff options
Diffstat (limited to 'src/scalar_impl.h')
| -rw-r--r-- | src/scalar_impl.h | 40 |
1 files changed, 25 insertions, 15 deletions
diff --git a/src/scalar_impl.h b/src/scalar_impl.h index 33824983e4..88ea97de86 100644 --- a/src/scalar_impl.h +++ b/src/scalar_impl.h @@ -25,14 +25,14 @@ #endif #ifndef USE_NUM_NONE -static void secp256k1_scalar_get_num(secp256k1_num_t *r, const secp256k1_scalar_t *a) { +static void secp256k1_scalar_get_num(secp256k1_num *r, const secp256k1_scalar *a) { unsigned char c[32]; secp256k1_scalar_get_b32(c, a); secp256k1_num_set_bin(r, c, 32); } /** secp256k1 curve order, see secp256k1_ecdsa_const_order_as_fe in ecdsa_impl.h */ -static void secp256k1_scalar_order_get_num(secp256k1_num_t *r) { +static void secp256k1_scalar_order_get_num(secp256k1_num *r) { static const unsigned char order[32] = { 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE, @@ -43,11 +43,11 @@ static void secp256k1_scalar_order_get_num(secp256k1_num_t *r) { } #endif -static void secp256k1_scalar_inverse(secp256k1_scalar_t *r, const secp256k1_scalar_t *x) { - secp256k1_scalar_t *t; +static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *x) { + secp256k1_scalar *t; int i; /* First compute x ^ (2^N - 1) for some values of N. */ - secp256k1_scalar_t x2, x3, x4, x6, x7, x8, x15, x30, x60, x120, x127; + secp256k1_scalar x2, x3, x4, x6, x7, x8, x15, x30, x60, x120, x127; secp256k1_scalar_sqr(&x2, x); secp256k1_scalar_mul(&x2, &x2, x); @@ -234,18 +234,27 @@ static void secp256k1_scalar_inverse(secp256k1_scalar_t *r, const secp256k1_scal secp256k1_scalar_mul(r, t, &x6); /* 111111 */ } -static void secp256k1_scalar_inverse_var(secp256k1_scalar_t *r, const secp256k1_scalar_t *x) { +SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a) { + /* d[0] is present and is the lowest word for all representations */ + return !(a->d[0] & 1); +} + +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_t n, m; - secp256k1_scalar_get_b32(b, x); + 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 @@ -290,30 +299,31 @@ static void secp256k1_scalar_inverse_var(secp256k1_scalar_t *r, const secp256k1_ * The function below splits a in r1 and r2, such that r1 + lambda * r2 == a (mod order). */ -static void secp256k1_scalar_split_lambda_var(secp256k1_scalar_t *r1, secp256k1_scalar_t *r2, const secp256k1_scalar_t *a) { - secp256k1_scalar_t c1, c2; - static const secp256k1_scalar_t minus_lambda = SECP256K1_SCALAR_CONST( +static void secp256k1_scalar_split_lambda(secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *a) { + secp256k1_scalar c1, c2; + static const secp256k1_scalar minus_lambda = SECP256K1_SCALAR_CONST( 0xAC9C52B3UL, 0x3FA3CF1FUL, 0x5AD9E3FDUL, 0x77ED9BA4UL, 0xA880B9FCUL, 0x8EC739C2UL, 0xE0CFC810UL, 0xB51283CFUL ); - static const secp256k1_scalar_t minus_b1 = SECP256K1_SCALAR_CONST( + static const secp256k1_scalar minus_b1 = SECP256K1_SCALAR_CONST( 0x00000000UL, 0x00000000UL, 0x00000000UL, 0x00000000UL, 0xE4437ED6UL, 0x010E8828UL, 0x6F547FA9UL, 0x0ABFE4C3UL ); - static const secp256k1_scalar_t minus_b2 = SECP256K1_SCALAR_CONST( + static const secp256k1_scalar minus_b2 = SECP256K1_SCALAR_CONST( 0xFFFFFFFFUL, 0xFFFFFFFFUL, 0xFFFFFFFFUL, 0xFFFFFFFEUL, 0x8A280AC5UL, 0x0774346DUL, 0xD765CDA8UL, 0x3DB1562CUL ); - static const secp256k1_scalar_t g1 = SECP256K1_SCALAR_CONST( + static const secp256k1_scalar g1 = SECP256K1_SCALAR_CONST( 0x00000000UL, 0x00000000UL, 0x00000000UL, 0x00003086UL, 0xD221A7D4UL, 0x6BCDE86CUL, 0x90E49284UL, 0xEB153DABUL ); - static const secp256k1_scalar_t g2 = SECP256K1_SCALAR_CONST( + static const secp256k1_scalar g2 = SECP256K1_SCALAR_CONST( 0x00000000UL, 0x00000000UL, 0x00000000UL, 0x0000E443UL, 0x7ED6010EUL, 0x88286F54UL, 0x7FA90ABFUL, 0xE4C42212UL ); VERIFY_CHECK(r1 != a); VERIFY_CHECK(r2 != a); + /* these _var calls are constant time since the shift amount is constant */ secp256k1_scalar_mul_shift_var(&c1, a, &g1, 272); secp256k1_scalar_mul_shift_var(&c2, a, &g2, 272); secp256k1_scalar_mul(&c1, &c1, &minus_b1); |