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
  19     EXAMPLES:
  20     **********
  21     IMPORTING:
  22     -----------
  23     >>> from CryptoPlus.Cipher import python_DES
  24
  25     EXAMPLE (test vectors from NESSIE):
  26     -----------------------------------
  27     >>> cipher = python_DES.new(('7CA110454A1A6E57').decode('hex'))
  28     >>> ciphertext = cipher.encrypt(('01A1D6D039776742').decode('hex'))
  29     >>> (ciphertext).encode('hex')
  30     '690f5b0d9a26939b'
  31     >>> plaintext = cipher.decrypt(ciphertext)
  32     >>> (plaintext).encode('hex')
  33     '01a1d6d039776742'
  34     """
  35     return python_DES(key,mode,IV,counter,segment_size)
  36
  37 class python_DES(BlockCipher):
  38     key_error_message = ("Key should be 64 bits")
  39
  40     def __init__(self,key,mode,IV,counter,segment_size):
  41         cipher_module = pyDes.des
  42         self.blocksize = 8
  43         BlockCipher.__init__(self,key,mode,IV,counter,cipher_module,segment_size)
  44
  45     def keylen_valid(self,key):
  46         return len(key) == 8
  47
  48 def _test():
  49     import doctest
  50     doctest.testmod()
  51
  52 if __name__ == "__main__":
  53     _test()