# coding: utf-8
# PyGOST -- Pure Python GOST cryptographic functions library
-# Copyright (C) 2015-2020 Sergey Matveev <stargrave@stargrave.org>
+# Copyright (C) 2015-2024 Sergey Matveev <stargrave@stargrave.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
return bytes2long(ukm[::-1])
-def kek(curve, prv, pub, ukm):
+def kek(curve, prv, pub, ukm, mask=None):
+ if not curve.contains(pub):
+ raise ValueError("pub is not on the curve")
key = curve.exp(prv, pub[0], pub[1])
key = curve.exp(curve.cofactor * ukm, key[0], key[1])
+ if mask is not None:
+ key = curve.exp(mask, key[0], key[1])
return pub_marshal(key)