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Abstract out verify logic for fe_negate

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This commit is contained in:
Pieter Wuille
2022-01-28 18:27:38 -05:00
parent 144670893e
commit 65d82a3445
4 changed files with 29 additions and 22 deletions
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15
src/field_10x26_impl.h
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@@ -349,15 +349,15 @@ static void secp256k1_fe_impl_get_b32(unsigned char *r, const secp256k1_fe *a) {
r[31] = a->n[0] & 0xff;
}
SECP256K1_INLINE static void secp256k1_fe_negate(secp256k1_fe *r, const secp256k1_fe *a, int m) {
#ifdef VERIFY
VERIFY_CHECK(a->magnitude <= m);
secp256k1_fe_verify(a);
SECP256K1_INLINE static void secp256k1_fe_impl_negate(secp256k1_fe *r, const secp256k1_fe *a, int m) {
/* For all legal values of m (0..31), the following properties hold: */
VERIFY_CHECK(0x3FFFC2FUL * 2 * (m + 1) >= 0x3FFFFFFUL * 2 * m);
VERIFY_CHECK(0x3FFFFBFUL * 2 * (m + 1) >= 0x3FFFFFFUL * 2 * m);
VERIFY_CHECK(0x3FFFFFFUL * 2 * (m + 1) >= 0x3FFFFFFUL * 2 * m);
VERIFY_CHECK(0x03FFFFFUL * 2 * (m + 1) >= 0x03FFFFFUL * 2 * m);
#endif
/* Due to the properties above, the left hand in the subtractions below is never less than
* the right hand. */
r->n[0] = 0x3FFFC2FUL * 2 * (m + 1) - a->n[0];
r->n[1] = 0x3FFFFBFUL * 2 * (m + 1) - a->n[1];
r->n[2] = 0x3FFFFFFUL * 2 * (m + 1) - a->n[2];
@@ -368,11 +368,6 @@ SECP256K1_INLINE static void secp256k1_fe_negate(secp256k1_fe *r, const secp256k
r->n[7] = 0x3FFFFFFUL * 2 * (m + 1) - a->n[7];
r->n[8] = 0x3FFFFFFUL * 2 * (m + 1) - a->n[8];
r->n[9] = 0x03FFFFFUL * 2 * (m + 1) - a->n[9];
#ifdef VERIFY
r->magnitude = m + 1;
r->normalized = 0;
secp256k1_fe_verify(r);
#endif
}
SECP256K1_INLINE static void secp256k1_fe_mul_int(secp256k1_fe *r, int a) {