frost/secp256k1-zkp
3
0
Fork 0
Code Issues Pull Requests Actions 2 Packages Projects Releases Wiki Activity

group: Avoid using infinity field directly in other modules

Browse Source
This commit is contained in:
Tim Ruffing
2025-10-28 15:00:58 +01:00
parent 7a2fff85e8
commit 2f73e5281d
5 changed files with 25 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
src/ecmult_const_impl.h
View File

@@ -87,17 +87,15 @@ static void secp256k1_ecmult_const_odd_multiples_table_globalz(secp256k1_ge *pre
secp256k1_fe neg_y; \
VERIFY_CHECK((n) < (1U << ECMULT_CONST_GROUP_SIZE)); \
VERIFY_CHECK(index < (1U << (ECMULT_CONST_GROUP_SIZE - 1))); \
/* Unconditionally set r->x = (pre)[m].x. r->y = (pre)[m].y. because it's either the correct one
/* Unconditionally set r->x = (pre)[m].x and r->y = (pre)[m].y because it's either the correct one
* or will get replaced in the later iterations, this is needed to make sure `r` is initialized. */ \
(r)->x = (pre)[m].x; \
(r)->y = (pre)[m].y; \
secp256k1_ge_set_xy((r), &(pre)[m].x, &(pre)[m].y); \
for (m = 1; m < ECMULT_CONST_TABLE_SIZE; m++) { \
/* This loop is used to avoid secret data in array indices. See
* the comment in ecmult_gen_impl.h for rationale. */ \
secp256k1_fe_cmov(&(r)->x, &(pre)[m].x, m == index); \
secp256k1_fe_cmov(&(r)->y, &(pre)[m].y, m == index); \
} \
(r)->infinity = 0; \
secp256k1_fe_negate(&neg_y, &(r)->y, 1); \
secp256k1_fe_cmov(&(r)->y, &neg_y, negative); \
} while(0)
@@ -375,11 +373,14 @@ static int secp256k1_ecmult_const_xonly(secp256k1_fe* r, const secp256k1_fe *n,
SECP256K1_FE_VERIFY_MAGNITUDE(&g, 2);
/* Compute base point P = (n*g, g^2), the effective affine version of (n*g, g^2, v), which has
* corresponding affine X coordinate n/d. */
secp256k1_fe_mul(&p.x, &g, n);
secp256k1_fe_sqr(&p.y, &g);
p.infinity = 0;
/* Compute base point P = (n*g, g^2), the effective affine version of
* (n*g, g^2, v), which has corresponding affine X coordinate n/d. */
{
secp256k1_fe x, y;
secp256k1_fe_mul(&x, &g, n);
secp256k1_fe_sqr(&y, &g);
secp256k1_ge_set_xy(&p, &x, &y);
}
/* Perform x-only EC multiplication of P with q. */
VERIFY_CHECK(!secp256k1_scalar_is_zero(q));