diff options
Diffstat (limited to 'pyecsca/ec/signature.py')
| -rw-r--r-- | pyecsca/ec/signature.py | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/pyecsca/ec/signature.py b/pyecsca/ec/signature.py index 8318c45..dbfb30d 100644 --- a/pyecsca/ec/signature.py +++ b/pyecsca/ec/signature.py @@ -92,8 +92,8 @@ class Signature(object): def _do_sign(self, nonce: Mod, digest: bytes) -> SignatureResult: z = int.from_bytes(digest, byteorder="big") - if z.bit_length() > self.mult.group.order.bit_length(): - z >>= z.bit_length() - self.mult.group.order.bit_length() + if len(digest) * 8 > self.mult.group.order.bit_length(): + z >>= len(digest) * 8 - self.mult.group.order.bit_length() point = self.mult.multiply(int(nonce), self.mult.group.generator) affine_point = point.to_affine() # TODO: add to context r = Mod(int(affine_point.x), self.mult.group.order) @@ -121,8 +121,8 @@ class Signature(object): def _do_verify(self, signature: SignatureResult, digest: bytes) -> bool: z = int.from_bytes(digest, byteorder="big") - if z.bit_length() > self.mult.group.order.bit_length(): - z >>= z.bit_length() - self.mult.group.order.bit_length() + if len(digest) * 8 > self.mult.group.order.bit_length(): + z >>= len(digest) * 8 - self.mult.group.order.bit_length() c = Mod(signature.s, self.mult.group.order).inverse() u1 = Mod(z, self.mult.group.order) * c u2 = Mod(signature.r, self.mult.group.order) * c |