# coding: utf-8
# PyGOST -- Pure Python GOST cryptographic functions library
-# Copyright (C) 2015-2016 Sergey Matveev <stargrave@stargrave.org>
+# Copyright (C) 2015-2023 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
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
+# the Free Software Foundation, version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
-"""Diffie-Hellman functions, VKO GOST R 34.10-2001/2012
+"""Key agreement functions, VKO GOST R 34.10-2001/2012
"""
from pygost.gost3410 import pub_marshal
from pygost.utils import bytes2long
-def vko_34102001(curve, prv, pubkey, ukm):
- """ Make Diffie-Hellman computation (34.10-2001, 34.11-94)
+def ukm_unmarshal(ukm):
+ """Unmarshal UKM value
+
+ :type ukm: little-endian bytes
+ :rtype: long
+ """
+ return bytes2long(ukm[::-1])
+
+
+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)
+
+
+def kek_34102001(curve, prv, pub, ukm):
+ """Key agreement (34.10-2001, 34.11-94)
:param GOST3410Curve curve: curve to use
:param long prv: private key
- :param pubkey: public key
- :type pubkey: (long, long)
- :param ukm: UKM value (VKO-factor)
- :type ukm: bytes, 8 bytes
+ :param pub: public key
+ :type pub: (long, long)
+ :param long ukm: user keying material, VKO-factor
:returns: Key Encryption Key (shared key)
:rtype: bytes, 32 bytes
:rfc:`4357` VKO GOST R 34.10-2001 with little-endian
hash output.
"""
- key = curve.exp(prv, pubkey[0], pubkey[1])
- key = curve.exp(bytes2long(24 * b"\x00" + ukm), key[0], key[1])
- return GOST341194(pub_marshal(key), "GostR3411_94_CryptoProParamSet").digest()
+ return GOST341194(
+ kek(curve, prv, pub, ukm),
+ sbox="id-GostR3411-94-CryptoProParamSet",
+ ).digest()
-def vko_34102012256(curve, prv, pubkey, ukm=b"\x00\x00\x00\x00\x00\x00\x00\01"):
- """ Make Diffie-Hellman computation (34.10-2012, 34.11-2012 256 bit)
+def kek_34102012256(curve, prv, pub, ukm=1):
+ """Key agreement (34.10-2012, 34.11-2012 256 bit)
:param GOST3410Curve curve: curve to use
:param long prv: private key
- :param pubkey: public key
- :type pubkey: (long, long)
- :param ukm: UKM value (VKO-factor)
- :type ukm: bytes, 8 bytes
+ :param pub: public key
+ :type pub: (long, long)
+ :param long ukm: user keying material, VKO-factor
:returns: Key Encryption Key (shared key)
:rtype: bytes, 32 bytes
+
+ Shared Key Encryption Key computation is based on
+ :rfc:`7836` VKO GOST R 34.10-2012.
"""
- key = curve.exp(prv, pubkey[0], pubkey[1])
- key = curve.exp(bytes2long(ukm[::-1]), key[0], key[1])
- return GOST34112012256(pub_marshal(key, mode=2012)).digest()
+ return GOST34112012256(kek(curve, prv, pub, ukm)).digest()
-def vko_34102012512(curve, prv, pubkey, ukm=b"\x00\x00\x00\x00\x00\x00\x00\01"):
- """ Make Diffie-Hellman computation (34.10-2012, 34.11-2012 512 bit)
+def kek_34102012512(curve, prv, pub, ukm=1):
+ """Key agreement (34.10-2012, 34.11-2012 512 bit)
:param GOST3410Curve curve: curve to use
:param long prv: private key
- :param pubkey: public key
- :type pubkey: (long, long)
- :param ukm: UKM value (VKO-factor)
- :type ukm: bytes, 8 bytes
+ :param pub: public key
+ :type pub: (long, long)
+ :param long ukm: user keying material, VKO-factor
:returns: Key Encryption Key (shared key)
:rtype: bytes, 32 bytes
+
+ Shared Key Encryption Key computation is based on
+ :rfc:`7836` VKO GOST R 34.10-2012.
"""
- key = curve.exp(prv, pubkey[0], pubkey[1])
- key = curve.exp(bytes2long(ukm[::-1]), key[0], key[1])
- return GOST34112012512(pub_marshal(key, mode=2012)).digest()
+ return GOST34112012512(kek(curve, prv, pub, ukm)).digest()