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Fixup skew before global Z fixup

This commit is contained in:
Peter Dettman 2021-12-26 14:56:28 +07:00
parent 40b624c90b
commit e82144edfb
1 changed files with 9 additions and 12 deletions
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21
src/ecmult_const_impl.h
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@ -213,25 +213,22 @@ static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, cons
}
}
secp256k1_fe_mul(&r->z, &r->z, &Z);
{
/* Correct for wNAF skew */
secp256k1_gej tmp;
secp256k1_ge a_1;
secp256k1_ge_neg(&a_1, a);
secp256k1_gej tmpj;
secp256k1_gej_add_ge(&tmp, r, &a_1);
secp256k1_gej_cmov(r, &tmp, skew_1);
secp256k1_ge_neg(&tmpa, &pre_a[0]);
secp256k1_gej_add_ge(&tmpj, r, &tmpa);
secp256k1_gej_cmov(r, &tmpj, skew_1);
if (size > 128) {
secp256k1_ge a_lam;
secp256k1_ge_mul_lambda(&a_lam, &a_1);
secp256k1_gej_add_ge(&tmp, r, &a_lam);
secp256k1_gej_cmov(r, &tmp, skew_lam);
secp256k1_ge_neg(&tmpa, &pre_a_lam[0]);
secp256k1_gej_add_ge(&tmpj, r, &tmpa);
secp256k1_gej_cmov(r, &tmpj, skew_lam);
}
}
secp256k1_fe_mul(&r->z, &r->z, &Z);
}
#endif /* SECP256K1_ECMULT_CONST_IMPL_H */