src/Cipher/python_DES.py

   1 from blockcipher import *
   2 import pyDes
   3
   4 def new(key,mode=MODE_ECB,IV=None,counter=None):
   5     """Create a new cipher object
   6
   7     wrapper for pure python implementation pyDes.py
   8
   9     new(key,mode=MODE_ECB,IV=None,counter=None):
  10         key = raw string containing the key
  11         mode = python_DES.MODE_ECB/CBC/CFB/OFB/CTR/XTS/CMAC, default is ECB
  12             -> for every mode, except ECB and CTR, it is important to construct a seperate cipher for encryption and decryption
  13         IV = IV as a raw string
  14             -> needed for CBC, CFB and OFB mode
  15         counter = counter object (CryptoPlus.Util.util.Counter)
  16             -> only needed for CTR mode
  17             -> use a seperate counter object for the cipher and decipher: the counter is updated directly, not a copy
  18                 see CTR example further on in the docstring
  19
  20
  21     EXAMPLE (test vectors from NESSIE):
  22     -----------------------------------
  23     >>> import python_DES
  24     >>> from binascii import hexlify, unhexlify
  25     >>> cipher = python_DES.new(unhexlify('7CA110454A1A6E57'))
  26     >>> ciphertext = cipher.encrypt(unhexlify('01A1D6D039776742'))
  27     >>> hexlify(ciphertext)
  28     '690f5b0d9a26939b'
  29     >>> plaintext = cipher.decrypt(ciphertext)
  30     >>> hexlify(plaintext)
  31     '01a1d6d039776742'
  32     """
  33     return python_DES(key,mode,IV,counter)
  34
  35 class python_DES(BlockCipher):
  36     def __init__(self,key,mode,IV,counter):
  37         self.cipher = pyDes.des(key)
  38         self.blocksize = self.cipher.block_size
  39         BlockCipher.__init__(self,key,mode,IV,counter)
  40
  41 def _test():
  42     import doctest
  43     doctest.testmod()
  44
  45 if __name__ == "__main__":
  46     _test()