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from .blockcipher import *
from . import pyDes
def new(key,mode=MODE_ECB,IV=None,counter=None,segment_size=None):
"""Create a new cipher object
wrapper for pure python implementation pyDes.py
key = raw string containing the key
mode = python_DES.MODE_ECB/CBC/CFB/OFB/CTR/CMAC, default is ECB
-> for every mode, except ECB and CTR, it is important to construct a seperate cipher for encryption and decryption
IV = IV as a raw string, default is "all zero" IV
-> needed for CBC, CFB and OFB mode
counter = counter object (CryptoPlus.Util.util.Counter)
-> only needed for CTR mode
-> use a seperate counter object for the cipher and decipher: the counter is updated directly, not a copy
see CTR example further on in the docstring
segment_size = amount of bits to use from the keystream in each chain part
-> supported values: multiple of 8 between 8 and the blocksize
of the cipher (only per byte access possible), default is 8
-> only needed for CFB mode
EXAMPLES:
**********
IMPORTING:
-----------
>>> import codecs
>>> from CryptoPlus.Cipher import python_DES
EXAMPLE (test vectors from NESSIE):
-----------------------------------
>>> cipher = python_DES.new(codecs.decode('7CA110454A1A6E57', 'hex'))
>>> ciphertext = cipher.encrypt(codecs.decode('01A1D6D039776742', 'hex'))
>>> codecs.encode(ciphertext, 'hex')
b'690f5b0d9a26939b'
>>> plaintext = cipher.decrypt(ciphertext)
>>> codecs.encode(plaintext, 'hex')
b'01a1d6d039776742'
"""
return python_DES(key,mode,IV,counter,segment_size)
class python_DES(BlockCipher):
key_error_message = ("Key should be 64 bits")
def __init__(self,key,mode,IV,counter,segment_size):
cipher_module = pyDes.des
self.blocksize = 8
BlockCipher.__init__(self,key,mode,IV,counter,cipher_module,segment_size)
def keylen_valid(self,key):
return len(key) == 8
def _test():
import doctest
doctest.testmod()
if __name__ == "__main__":
_test()