Abstract out verify logic for fe_is_odd

This commit is contained in:
Pieter Wuille 2022-01-28 18:11:21 -05:00
parent d3f3fe8616
commit c5e788d672
4 changed files with 15 additions and 11 deletions

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@ -83,6 +83,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
# define secp256k1_fe_set_int secp256k1_fe_impl_set_int # define secp256k1_fe_set_int secp256k1_fe_impl_set_int
# define secp256k1_fe_clear secp256k1_fe_impl_clear # define secp256k1_fe_clear secp256k1_fe_impl_clear
# define secp256k1_fe_is_zero secp256k1_fe_impl_is_zero # define secp256k1_fe_is_zero secp256k1_fe_impl_is_zero
# define secp256k1_fe_is_odd secp256k1_fe_impl_is_odd
#endif /* !defined(VERIFY) */ #endif /* !defined(VERIFY) */
/** Normalize a field element. /** Normalize a field element.
@ -142,7 +143,11 @@ static void secp256k1_fe_clear(secp256k1_fe *a);
*/ */
static int secp256k1_fe_is_zero(const secp256k1_fe *a); static int secp256k1_fe_is_zero(const secp256k1_fe *a);
/** Check the "oddness" of a field element. Requires the input to be normalized. */ /** Determine whether a (mod p) is odd.
*
* On input, a must be a valid normalized field element.
* Returns (int(a) mod p) & 1.
*/
static int secp256k1_fe_is_odd(const secp256k1_fe *a); static int secp256k1_fe_is_odd(const secp256k1_fe *a);
/** Compare two field elements. Requires magnitude-1 inputs. */ /** Compare two field elements. Requires magnitude-1 inputs. */

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@ -274,11 +274,7 @@ SECP256K1_INLINE static int secp256k1_fe_impl_is_zero(const secp256k1_fe *a) {
return (t[0] | t[1] | t[2] | t[3] | t[4] | t[5] | t[6] | t[7] | t[8] | t[9]) == 0; return (t[0] | t[1] | t[2] | t[3] | t[4] | t[5] | t[6] | t[7] | t[8] | t[9]) == 0;
} }
SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) { SECP256K1_INLINE static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
secp256k1_fe_verify(a);
#endif
return a->n[0] & 1; return a->n[0] & 1;
} }

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@ -220,11 +220,7 @@ SECP256K1_INLINE static int secp256k1_fe_impl_is_zero(const secp256k1_fe *a) {
return (t[0] | t[1] | t[2] | t[3] | t[4]) == 0; return (t[0] | t[1] | t[2] | t[3] | t[4]) == 0;
} }
SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) { SECP256K1_INLINE static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
secp256k1_fe_verify(a);
#endif
return a->n[0] & 1; return a->n[0] & 1;
} }

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@ -209,6 +209,13 @@ SECP256K1_INLINE static int secp256k1_fe_is_zero(const secp256k1_fe *a) {
VERIFY_CHECK(a->normalized); VERIFY_CHECK(a->normalized);
return secp256k1_fe_impl_is_zero(a); return secp256k1_fe_impl_is_zero(a);
} }
static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a);
SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
secp256k1_fe_verify(a);
VERIFY_CHECK(a->normalized);
return secp256k1_fe_impl_is_odd(a);
}
#endif /* defined(VERIFY) */ #endif /* defined(VERIFY) */
#endif /* SECP256K1_FIELD_IMPL_H */ #endif /* SECP256K1_FIELD_IMPL_H */