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Merge pull request #243

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bb0ea50 Replace set/add with cmov in secp256k1_gej_add_ge. (Gregory Maxwell)
This commit is contained in:
Pieter Wuille 2015-04-22 02:46:20 -07:00
commit 426fa52511
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GPG key ID: 57896D2FF8F0B657
4 changed files with 44 additions and 8 deletions
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3
src/field.h
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@ -113,4 +113,7 @@ static void secp256k1_fe_from_storage(secp256k1_fe_t *r, const secp256k1_fe_stor
/** If flag is true, set *r equal to *a; otherwise leave it. Constant-time. */
static void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag);
/** If flag is true, set *r equal to *a; otherwise leave it. Constant-time. */
static void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int flag);
#endif

20
src/field_10x26_impl.h
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@ -1068,6 +1068,26 @@ static void secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
#endif
}
static SECP256K1_INLINE void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int flag) {
uint32_t mask0, mask1;
mask0 = flag + ~((uint32_t)0);
mask1 = ~mask0;
r->n[0] = (r->n[0] & mask0) | (a->n[0] & mask1);
r->n[1] = (r->n[1] & mask0) | (a->n[1] & mask1);
r->n[2] = (r->n[2] & mask0) | (a->n[2] & mask1);
r->n[3] = (r->n[3] & mask0) | (a->n[3] & mask1);
r->n[4] = (r->n[4] & mask0) | (a->n[4] & mask1);
r->n[5] = (r->n[5] & mask0) | (a->n[5] & mask1);
r->n[6] = (r->n[6] & mask0) | (a->n[6] & mask1);
r->n[7] = (r->n[7] & mask0) | (a->n[7] & mask1);
r->n[8] = (r->n[8] & mask0) | (a->n[8] & mask1);
r->n[9] = (r->n[9] & mask0) | (a->n[9] & mask1);
#ifdef VERIFY
r->magnitude = (r->magnitude & mask0) | (a->magnitude & mask1);
r->normalized = (r->normalized & mask0) | (a->normalized & mask1);
#endif
}
static SECP256K1_INLINE void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag) {
uint32_t mask0, mask1;
mask0 = flag + ~((uint32_t)0);

15
src/field_5x52_impl.h
View file

@ -404,6 +404,21 @@ static void secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
#endif
}
static SECP256K1_INLINE void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int flag) {
uint64_t mask0, mask1;
mask0 = flag + ~((uint64_t)0);
mask1 = ~mask0;
r->n[0] = (r->n[0] & mask0) | (a->n[0] & mask1);
r->n[1] = (r->n[1] & mask0) | (a->n[1] & mask1);
r->n[2] = (r->n[2] & mask0) | (a->n[2] & mask1);
r->n[3] = (r->n[3] & mask0) | (a->n[3] & mask1);
r->n[4] = (r->n[4] & mask0) | (a->n[4] & mask1);
#ifdef VERIFY
r->magnitude = (r->magnitude & mask0) | (a->magnitude & mask1);
r->normalized = (r->normalized & mask0) | (a->normalized & mask1);
#endif
}
static SECP256K1_INLINE void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag) {
uint64_t mask0, mask1;
mask0 = flag + ~((uint64_t)0);

14
src/group_impl.h
View file

@ -325,7 +325,8 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej_t *r, const secp256k1_gej_t *
}
static void secp256k1_gej_add_ge(secp256k1_gej_t *r, const secp256k1_gej_t *a, const secp256k1_ge_t *b) {
/* Operations: 7 mul, 5 sqr, 5 normalize, 19 mul_int/add/negate */
/* Operations: 7 mul, 5 sqr, 5 normalize, 17 mul_int/add/negate/cmov */
static const secp256k1_fe_t fe_1 = SECP256K1_FE_CONST(0, 0, 0, 0, 0, 0, 0, 1);
secp256k1_fe_t zz, u1, u2, s1, s2, z, t, m, n, q, rr;
int infinity;
VERIFY_CHECK(!b->infinity);
@ -387,14 +388,11 @@ static void secp256k1_gej_add_ge(secp256k1_gej_t *r, const secp256k1_gej_t *a, c
secp256k1_fe_mul_int(&r->y, 4 * (1 - a->infinity)); /* r->y = Y3 = 4*R*(3*Q-2*R^2)-4*M^4 (4) */
/** In case a->infinity == 1, the above code results in r->x, r->y, and r->z all equal to 0.
* Add b->x to x, b->y to y, and 1 to z in that case.
* Replace r with b->x, b->y, 1 in that case.
*/
t = b->x; secp256k1_fe_mul_int(&t, a->infinity);
secp256k1_fe_add(&r->x, &t);
t = b->y; secp256k1_fe_mul_int(&t, a->infinity);
secp256k1_fe_add(&r->y, &t);
secp256k1_fe_set_int(&t, a->infinity);
secp256k1_fe_add(&r->z, &t);
secp256k1_fe_cmov(&r->x, &b->x, a->infinity);
secp256k1_fe_cmov(&r->y, &b->y, a->infinity);
secp256k1_fe_cmov(&r->z, &fe_1, a->infinity);
r->infinity = infinity;
}