openid-consumer/openid/dh.py

   1 from openid import cryptutil
   2 from openid import oidutil
   3
   4 def strxor(x, y):
   5     if len(x) != len(y):
   6         raise ValueError('Inputs to strxor must have the same length')
   7
   8     xor = lambda (a, b): chr(ord(a) ^ ord(b))
   9     return "".join(map(xor, zip(x, y)))
  10
  11 class DiffieHellman(object):
  12     DEFAULT_MOD = 155172898181473697471232257763715539915724801966915404479707795314057629378541917580651227423698188993727816152646631438561595825688188889951272158842675419950341258706556549803580104870537681476726513255747040765857479291291572334510643245094715007229621094194349783925984760375594985848253359305585439638443L
  13
  14     DEFAULT_GEN = 2
  15
  16     def fromDefaults(cls):
  17         return cls(cls.DEFAULT_MOD, cls.DEFAULT_GEN)
  18
  19     fromDefaults = classmethod(fromDefaults)
  20
  21     def __init__(self, modulus, generator):
  22         self.modulus = long(modulus)
  23         self.generator = long(generator)
  24
  25         self._setPrivate(cryptutil.randrange(1, modulus - 1))
  26
  27     def _setPrivate(self, private):
  28         """This is here to make testing easier"""
  29         self.private = private
  30         self.public = pow(self.generator, self.private, self.modulus)
  31
  32     def usingDefaultValues(self):
  33         return (self.modulus == self.DEFAULT_MOD and
  34                 self.generator == self.DEFAULT_GEN)
  35
  36     def getSharedSecret(self, composite):
  37         return pow(composite, self.private, self.modulus)
  38
  39     def xorSecret(self, composite, secret, hash_func):
  40         dh_shared = self.getSharedSecret(composite)
  41         hashed_dh_shared = hash_func(cryptutil.longToBinary(dh_shared))
  42         return strxor(secret, hashed_dh_shared)