src/CryptoPlus/Cipher/python_DES.py

   1 from blockcipher import *
   2 import pyDes
   3
   4 def new(key,mode=MODE_ECB,IV=None,counter=None,segment_size=None):
   5     """Create a new cipher object
   6
   7     wrapper for pure python implementation pyDes.py
   8
   9         key = raw string containing the key
  10         mode = python_DES.MODE_ECB/CBC/CFB/OFB/CTR/CMAC, default is ECB
  11             -> for every mode, except ECB and CTR, it is important to construct a seperate cipher for encryption and decryption
  12         IV = IV as a raw string, default is "all zero" IV
  13             -> needed for CBC, CFB and OFB mode
  14         counter = counter object (CryptoPlus.Util.util.Counter)
  15             -> only needed for CTR mode
  16             -> use a seperate counter object for the cipher and decipher: the counter is updated directly, not a copy
  17                 see CTR example further on in the docstring
  18         segment_size = amount of bits to use from the keystream in each chain part
  19             -> supported values: multiple of 8 between 8 and the blocksize
  20                of the cipher (only per byte access possible), default is 8
  21             -> only needed for CFB mode
  22
  23     EXAMPLES:
  24     **********
  25     IMPORTING:
  26     -----------
  27     >>> from CryptoPlus.Cipher import python_DES
  28
  29     EXAMPLE (test vectors from NESSIE):
  30     -----------------------------------
  31     >>> cipher = python_DES.new(('7CA110454A1A6E57').decode('hex'))
  32     >>> ciphertext = cipher.encrypt(('01A1D6D039776742').decode('hex'))
  33     >>> (ciphertext).encode('hex')
  34     '690f5b0d9a26939b'
  35     >>> plaintext = cipher.decrypt(ciphertext)
  36     >>> (plaintext).encode('hex')
  37     '01a1d6d039776742'
  38     """
  39     return python_DES(key,mode,IV,counter,segment_size)
  40
  41 class python_DES(BlockCipher):
  42     key_error_message = ("Key should be 64 bits")
  43
  44     def __init__(self,key,mode,IV,counter,segment_size):
  45         cipher_module = pyDes.des
  46         self.blocksize = 8
  47         BlockCipher.__init__(self,key,mode,IV,counter,cipher_module,segment_size)
  48
  49     def keylen_valid(self,key):
  50         return len(key) == 8
  51
  52 def _test():
  53     import doctest
  54     doctest.testmod()
  55
  56 if __name__ == "__main__":
  57     _test()