diff options
Diffstat (limited to 'src/secp256k1/src/field_impl.h')
-rw-r--r-- | src/secp256k1/src/field_impl.h | 36 |
1 files changed, 34 insertions, 2 deletions
diff --git a/src/secp256k1/src/field_impl.h b/src/secp256k1/src/field_impl.h index 77f4aae2f9..52cd902eb3 100644 --- a/src/secp256k1/src/field_impl.h +++ b/src/secp256k1/src/field_impl.h @@ -21,6 +21,13 @@ #error "Please select field implementation" #endif +SECP256K1_INLINE static int secp256k1_fe_equal(const secp256k1_fe *a, const secp256k1_fe *b) { + secp256k1_fe na; + secp256k1_fe_negate(&na, a, 1); + secp256k1_fe_add(&na, b); + return secp256k1_fe_normalizes_to_zero(&na); +} + SECP256K1_INLINE static int secp256k1_fe_equal_var(const secp256k1_fe *a, const secp256k1_fe *b) { secp256k1_fe na; secp256k1_fe_negate(&na, a, 1); @@ -28,7 +35,7 @@ SECP256K1_INLINE static int secp256k1_fe_equal_var(const secp256k1_fe *a, const return secp256k1_fe_normalizes_to_zero_var(&na); } -static int secp256k1_fe_sqrt_var(secp256k1_fe *r, const secp256k1_fe *a) { +static int secp256k1_fe_sqrt(secp256k1_fe *r, const secp256k1_fe *a) { /** Given that p is congruent to 3 mod 4, we can compute the square root of * a mod p as the (p+1)/4'th power of a. * @@ -123,7 +130,7 @@ static int secp256k1_fe_sqrt_var(secp256k1_fe *r, const secp256k1_fe *a) { /* Check that a square root was actually calculated */ secp256k1_fe_sqr(&t1, r); - return secp256k1_fe_equal_var(&t1, a); + return secp256k1_fe_equal(&t1, a); } static void secp256k1_fe_inv(secp256k1_fe *r, const secp256k1_fe *a) { @@ -280,4 +287,29 @@ static void secp256k1_fe_inv_all_var(size_t len, secp256k1_fe *r, const secp256k r[0] = u; } +static int secp256k1_fe_is_quad_var(const secp256k1_fe *a) { +#ifndef USE_NUM_NONE + unsigned char b[32]; + secp256k1_num n; + secp256k1_num m; + /* secp256k1 field prime, value p defined in "Standards for Efficient Cryptography" (SEC2) 2.7.1. */ + static const unsigned char prime[32] = { + 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, + 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, + 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, + 0xFF,0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F + }; + + secp256k1_fe c = *a; + secp256k1_fe_normalize_var(&c); + secp256k1_fe_get_b32(b, &c); + secp256k1_num_set_bin(&n, b, 32); + secp256k1_num_set_bin(&m, prime, 32); + return secp256k1_num_jacobi(&n, &m) >= 0; +#else + secp256k1_fe r; + return secp256k1_fe_sqrt(&r, a); +#endif +} + #endif |