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Faster P256.pointAdd

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Convert to projective coordinates without expansive calls to function
'scalar_mult'.
This commit is contained in:
Olivier Chéron 2019-08-21 09:32:53 +02:00
parent 0d32f9b833
commit 4ca77b8cf5
1 changed files with 3 additions and 6 deletions
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9
cbits/p256/p256_ec.c
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@ -1287,19 +1287,16 @@ void cryptonite_p256e_point_add(
const cryptonite_p256_int *in_x2, const cryptonite_p256_int *in_y2,
cryptonite_p256_int *out_x, cryptonite_p256_int *out_y)
{
felem x1, y1, z1, x2, y2, z2, px1, py1, px2, py2;
const cryptonite_p256_int one = P256_ONE;
felem x, y, z, px1, py1, px2, py2;
to_montgomery(px1, in_x1);
to_montgomery(py1, in_y1);
to_montgomery(px2, in_x2);
to_montgomery(py2, in_y2);
scalar_mult(x1, y1, z1, px1, py1, &one);
scalar_mult(x2, y2, z2, px2, py2, &one);
point_add_or_double_vartime(x1, y1, z1, x1, y1, z1, x2, y2, z2);
point_add_or_double_vartime(x, y, z, px1, py1, kOne, px2, py2, kOne);
point_to_affine(px1, py1, x1, y1, z1);
point_to_affine(px1, py1, x, y, z);
from_montgomery(out_x, px1);
from_montgomery(out_y, py1);
}