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Implement endomorphism optimization for secp256k1_ecmult_const

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This commit is contained in:
Andrew Poelstra
2015-05-22 12:09:36 -05:00
parent ed35d43a0c
commit 92e53fc4c8
3 changed files with 144 additions and 14 deletions
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19
src/tests.c
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@@ -1550,10 +1550,21 @@ void test_constant_wnaf(const secp256k1_scalar_t *number, int w) {
secp256k1_scalar_t x, shift;
int wnaf[256] = {0};
int i;
#ifdef USE_ENDOMORPHISM
int skew;
#endif
secp256k1_scalar_t num = *number;
secp256k1_scalar_set_int(&x, 0);
secp256k1_scalar_set_int(&shift, 1 << w);
secp256k1_wnaf_const(wnaf, number, w);
/* With USE_ENDOMORPHISM on we only consider 128-bit numbers */
#ifdef USE_ENDOMORPHISM
for (i = 0; i < 16; ++i)
secp256k1_scalar_shr_int(&num, 8);
skew = secp256k1_wnaf_const(wnaf, num, w);
#else
secp256k1_wnaf_const(wnaf, num, w);
#endif
for (i = WNAF_SIZE(w); i >= 0; --i) {
secp256k1_scalar_t t;
@@ -1572,7 +1583,11 @@ void test_constant_wnaf(const secp256k1_scalar_t *number, int w) {
}
secp256k1_scalar_add(&x, &x, &t);
}
CHECK(secp256k1_scalar_eq(&x, number));
#ifdef USE_ENDOMORPHISM
/* Skew num because when encoding 128-bit numbers as odd we use an offset */
secp256k1_scalar_cadd_bit(&num, skew == 2, 1);
#endif
CHECK(secp256k1_scalar_eq(&x, &num));
}
void run_wnaf(void) {