src/CryptoPlus/Cipher/python_Serpent.py

   1 from blockcipher import *
   2 from pyserpent import Serpent
   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 pyserpent.py
   8
   9         key = raw string containing the key
  10             -> when using XTS mode: the key should be a tuple containing the 2 keys needed
  11         mode = python_Serpent.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     EXAMPLES:
  21     **********
  22     IMPORTING:
  23     -----------
  24     >>> from CryptoPlus.Cipher import python_Serpent
  25
  26     EXAMPLE:
  27     ---------
  28     NESSIE Test Vectors: http://www.cs.technion.ac.il/~biham/Reports/Serpent/Serpent-128-128.verified.test-vectors
  29
  30     >>> cipher = python_Serpent.new(('000102030405060708090A0B0C0D0E0F').decode('hex'))
  31     >>> (cipher.encrypt(('33B3DC87EDDD9B0F6A1F407D14919365').decode('hex'))).encode('hex').upper()
  32     '00112233445566778899AABBCCDDEEFF'
  33     >>> ( cipher.decrypt((_).decode('hex')) ).encode('hex').upper()
  34     '33B3DC87EDDD9B0F6A1F407D14919365'
  35
  36     >>> cipher = python_Serpent.new(('FDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFD').decode('hex'))
  37     >>> (cipher.encrypt(('FDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFD').decode('hex'))).encode('hex').upper()
  38     '81F9163BDF39B5BB2932AB91DF2A5FFC'
  39     >>> ( cipher.decrypt((_).decode('hex')) ).encode('hex').upper()
  40     'FDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFD'
  41
  42     CBC EXAMPLE:
  43     -------------
  44     >>> key = ('000102030405060708090A0B0C0D0E0F').decode('hex')
  45     >>> IV = ('00000000000000000000000000000000').decode('hex')
  46     >>> plaintext = ('33B3DC87EDDD9B0F6A1F407D14919365'*3).decode('hex')
  47     >>> cipher = python_Serpent.new(key,python_Serpent.MODE_CBC,IV)
  48     >>> ciphertext = cipher.encrypt(plaintext)
  49     >>> decipher = python_Serpent.new(key,python_Serpent.MODE_CBC,IV)
  50     >>> ( decipher.decrypt(ciphertext)).encode('hex').upper()
  51     '33B3DC87EDDD9B0F6A1F407D1491936533B3DC87EDDD9B0F6A1F407D1491936533B3DC87EDDD9B0F6A1F407D14919365'
  52     """
  53     return python_Serpent(key,mode,IV,counter)
  54
  55 class python_Serpent(BlockCipher):
  56     def __init__(self,key,mode,IV,counter):
  57         if len(key) not in (16,24,32) and type(key) is not tuple:
  58                 raise ValueError("Key should be 128, 192 or 256 bits")
  59         cipher_module = Serpent
  60         self.blocksize = 16
  61         BlockCipher.__init__(self,key,mode,IV,counter,cipher_module)
  62
  63 def _test():
  64     import doctest
  65     doctest.testmod()
  66
  67 if __name__ == "__main__":
  68     _test()