python实现的DES加密算法和3DES加密算法实例

本文实例讲述了python实现的DES加密算法和3DES加密算法。分享给大家供大家参考。具体实现方法如下：

#############################################################################
#         Documentation          #
#############################################################################
# Author:  Todd Whiteman
# Date:   16th March, 2009
# Verion:  2.0.0
# License: Public Domain - free to do as you wish
# Homepage: http://twhiteman.netfirms.com/des.html
#
# This is a pure python implementation of the DES encryption algorithm.
# It's pure python to avoid portability issues, since most DES
# implementations are programmed in C (for performance reasons).
#
# Triple DES class is also implemented, utilising the DES base. Triple DES
# is either DES-EDE3 with a 24 byte key, or DES-EDE2 with a 16 byte key.
#
# See the README.txt that should come with this python module for the
# implementation methods used.
#
# Thanks to:
# * David Broadwell for ideas, comments and suggestions.
# * Mario Wolff for pointing out and debugging some triple des CBC errors.
# * Santiago Palladino for providing the PKCS5 padding technique.
# * Shaya for correcting the PAD_PKCS5 triple des CBC errors.
#
"""A pure python implementation of the DES and TRIPLE DES encryption algorithms.
Class initialization
--------------------
pyDes.des(key, [mode], [IV], [pad], [padmode])
pyDes.triple_des(key, [mode], [IV], [pad], [padmode])
key   -> Bytes containing the encryption key. 8 bytes for DES, 16 or 24 bytes
   for Triple DES
mode  -> Optional argument for encryption type, can be either
   pyDes.ECB (Electronic Code Book) or pyDes.CBC (Cypher Block Chaining)
IV   -> Optional Initial Value bytes, must be supplied if using CBC mode.
   Length must be 8 bytes.
pad   -> Optional argument, set the pad character (PAD_NORMAL) to use during
   all encrypt/decrpt operations done with this instance.
padmode -> Optional argument, set the padding mode (PAD_NORMAL or PAD_PKCS5)
   to use during all encrypt/decrpt operations done with this instance.
I recommend to use PAD_PKCS5 padding, as then you never need to worry about any
padding issues, as the padding can be removed unambiguously upon decrypting
data that was encrypted using PAD_PKCS5 padmode.
Common methods
--------------
encrypt(data, [pad], [padmode])
decrypt(data, [pad], [padmode])
data  -> Bytes to be encrypted/decrypted
pad   -> Optional argument. Only when using padmode of PAD_NORMAL. For
   encryption, adds this characters to the end of the data block when
   data is not a multiple of 8 bytes. For decryption, will remove the
   trailing characters that match this pad character from the last 8
   bytes of the unencrypted data block.
padmode -> Optional argument, set the padding mode, must be one of PAD_NORMAL
   or PAD_PKCS5). Defaults to PAD_NORMAL.

Example
-------
from pyDes import *
data = "Please encrypt my data"
k = des("DESCRYPT", CBC, "\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
# For Python3, you'll need to use bytes, i.e.:
#  data = b"Please encrypt my data"
#  k = des(b"DESCRYPT", CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
d = k.encrypt(data)
print "Encrypted: ％r" ％ d
print "Decrypted: ％r" ％ k.decrypt(d)
assert k.decrypt(d, padmode=PAD_PKCS5) == data

See the module source (pyDes.py) for more examples of use.
You can also run the pyDes.py file without and arguments to see a simple test.
Note: This code was not written for high-end systems needing a fast
  implementation, but rather a handy portable solution with small usage.
"""
import sys
# _pythonMajorVersion is used to handle Python2 and Python3 differences.
_pythonMajorVersion = sys.version_info[0]
# Modes of crypting / cyphering
ECB =  0
CBC =  1
# Modes of padding
PAD_NORMAL = 1
PAD_PKCS5 = 2
# PAD_PKCS5: is a method that will unambiguously remove all padding
#      characters after decryption, when originally encrypted with
#      this padding mode.
# For a good description of the PKCS5 padding technique, see:
# http://www.faqs.org/rfcs/rfc1423.html
# The base class shared by des and triple des.
class _baseDes(object):
 def __init__(self, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL):
   if IV:
     IV = self._guardAgainstUnicode(IV)
   if pad:
     pad = self._guardAgainstUnicode(pad)
   self.block_size = 8
   # Sanity checking of arguments.
   if pad and padmode == PAD_PKCS5:
     raise ValueError("Cannot use a pad character with PAD_PKCS5")
   if IV and len(IV) != self.block_size:
     raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes")
   # Set the passed in variables
   self._mode = mode
   self._iv = IV
   self._padding = pad
   self._padmode = padmode
 def getKey(self):
   """getKey() -> bytes"""
   return self.__key
 def setKey(self, key):
   """Will set the crypting key for this object."""
   key = self._guardAgainstUnicode(key)
   self.__key = key
 def getMode(self):
   """getMode() -> pyDes.ECB or pyDes.CBC"""
   return self._mode
 def setMode(self, mode):
   """Sets the type of crypting mode, pyDes.ECB or pyDes.CBC"""
   self._mode = mode
 def getPadding(self):
   """getPadding() -> bytes of length 1. Padding character."""
   return self._padding
 def setPadding(self, pad):
   """setPadding() -> bytes of length 1. Padding character."""
   if pad is not None:
     pad = self._guardAgainstUnicode(pad)
   self._padding = pad
 def getPadMode(self):
   """getPadMode() -> pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
   return self._padmode
 def setPadMode(self, mode):
   """Sets the type of padding mode, pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
   self._padmode = mode
 def getIV(self):
   """getIV() -> bytes"""
   return self._iv
 def setIV(self, IV):
   """Will set the Initial Value, used in conjunction with CBC mode"""
   if not IV or len(IV) != self.block_size:
     raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes")
   IV = self._guardAgainstUnicode(IV)
   self._iv = IV
 def _padData(self, data, pad, padmode):
   # Pad data depending on the mode
   if padmode is None:
     # Get the default padding mode.
     padmode = self.getPadMode()
   if pad and padmode == PAD_PKCS5:
     raise ValueError("Cannot use a pad character with PAD_PKCS5")
   if padmode == PAD_NORMAL:
     if len(data) ％ self.block_size == 0:
       # No padding required.
       return data
     if not pad:
       # Get the default padding.
       pad = self.getPadding()
     if not pad:
       raise ValueError("Data must be a multiple of " + str(self.block_size) + " bytes in length. Use padmode=PAD_PKCS5 or set the pad character.")
     data += (self.block_size - (len(data) ％ self.block_size)) * pad
   elif padmode == PAD_PKCS5:
     pad_len = 8 - (len(data) ％ self.block_size)
     if _pythonMajorVersion < 3:
       data += pad_len * chr(pad_len)
     else:
       data += bytes([pad_len] * pad_len)
   return data
 def _unpadData(self, data, pad, padmode):
   # Unpad data depending on the mode.
   if not data:
     return data
   if pad and padmode == PAD_PKCS5:
     raise ValueError("Cannot use a pad character with PAD_PKCS5")
   if padmode is None:
     # Get the default padding mode.
     padmode = self.getPadMode()
   if padmode == PAD_NORMAL:
     if not pad:
       # Get the default padding.
       pad = self.getPadding()
     if pad:
       data = data[:-self.block_size] + \
           data[-self.block_size:].rstrip(pad)
   elif padmode == PAD_PKCS5:
     if _pythonMajorVersion < 3:
       pad_len = ord(data[-1])
     else:
       pad_len = data[-1]
     data = data[:-pad_len]
   return data
 def _guardAgainstUnicode(self, data):
   # Only accept byte strings or ascii unicode values, otherwise
   # there is no way to correctly decode the data into bytes.
   if _pythonMajorVersion < 3:
     if isinstance(data, unicode):
       raise ValueError("pyDes can only work with bytes, not Unicode strings.")
   else:
     if isinstance(data, str):
       # Only accept ascii unicode values.
       try:
         return data.encode('ascii')
       except UnicodeEncodeError:
         pass
       raise ValueError("pyDes can only work with encoded strings, not Unicode.")
   return data
#############################################################################
#           DES            #
#############################################################################
class des(_baseDes):
 """DES encryption/decrytpion class
 Supports ECB (Electronic Code Book) and CBC (Cypher Block Chaining) modes.
 pyDes.des(key,[mode], [IV])
 key -> Bytes containing the encryption key, must be exactly 8 bytes
 mode -> Optional argument for encryption type, can be either pyDes.ECB
   (Electronic Code Book), pyDes.CBC (Cypher Block Chaining)
 IV  -> Optional Initial Value bytes, must be supplied if using CBC mode.
   Must be 8 bytes in length.
 pad -> Optional argument, set the pad character (PAD_NORMAL) to use
   during all encrypt/decrpt operations done with this instance.
 padmode -> Optional argument, set the padding mode (PAD_NORMAL or
   PAD_PKCS5) to use during all encrypt/decrpt operations done
   with this instance.
 """

# Permutation and translation tables for DES
 __pc1 = [56, 48, 40, 32, 24, 16, 8,
, 57, 49, 41, 33, 25, 17,
, 1, 58, 50, 42, 34, 26,
, 10, 2, 59, 51, 43, 35,
, 54, 46, 38, 30, 22, 14,
, 61, 53, 45, 37, 29, 21,
, 5, 60, 52, 44, 36, 28,
, 12, 4, 27, 19, 11, 3
 ]
 # number left rotations of pc1
 __left_rotations = [
, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
 ]
 # permuted choice key (table 2)
 __pc2 = [
, 16, 10, 23, 0, 4,
, 27, 14, 5, 20, 9,
, 18, 11, 3, 25, 7,
, 6, 26, 19, 12, 1,
, 51, 30, 36, 46, 54,
, 39, 50, 44, 32, 47,
, 48, 38, 55, 33, 52,
, 41, 49, 35, 28, 31
 ]
 # initial permutation IP
 __ip = [57, 49, 41, 33, 25, 17, 9, 1,
, 51, 43, 35, 27, 19, 11, 3,
, 53, 45, 37, 29, 21, 13, 5,
, 55, 47, 39, 31, 23, 15, 7,
, 48, 40, 32, 24, 16, 8, 0,
, 50, 42, 34, 26, 18, 10, 2,
, 52, 44, 36, 28, 20, 12, 4,
, 54, 46, 38, 30, 22, 14, 6
 ]
 # Expansion table for turning 32 bit blocks into 48 bits
 __expansion_table = [
, 0, 1, 2, 3, 4,
, 4, 5, 6, 7, 8,
, 8, 9, 10, 11, 12,
, 12, 13, 14, 15, 16,
, 16, 17, 18, 19, 20,
, 20, 21, 22, 23, 24,
, 24, 25, 26, 27, 28,
, 28, 29, 30, 31, 0
 ]
 # The (in)famous S-boxes
 __sbox = [
   # S1
   [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],
   # S2
   [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],
   # S3
   [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],
   # S4
   [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],
   # S5
   [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],
   # S6
   [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],
   # S7
   [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],
   # S8
   [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
 ]

# 32-bit permutation function P used on the output of the S-boxes
 __p = [
, 6, 19, 20, 28, 11,
, 16, 0, 14, 22, 25,
, 17, 30, 9, 1, 7,
,13, 31, 26, 2, 8,
, 12, 29, 5, 21, 10,
, 24
 ]
 # final permutation IP^-1
 __fp = [
, 7, 47, 15, 55, 23, 63, 31,
, 6, 46, 14, 54, 22, 62, 30,
, 5, 45, 13, 53, 21, 61, 29,
, 4, 44, 12, 52, 20, 60, 28,
, 3, 43, 11, 51, 19, 59, 27,
, 2, 42, 10, 50, 18, 58, 26,
, 1, 41, 9, 49, 17, 57, 25,
, 0, 40, 8, 48, 16, 56, 24
 ]
 # Type of crypting being done
 ENCRYPT =  0x00
 DECRYPT =  0x01
 # Initialisation
 def __init__(self, key, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL):
   # Sanity checking of arguments.
   if len(key) != 8:
     raise ValueError("Invalid DES key size. Key must be exactly 8 bytes long.")
   _baseDes.__init__(self, mode, IV, pad, padmode)
   self.key_size = 8
   self.L = []
   self.R = []
   self.Kn = [ [0] * 48 ] * 16  # 16 48-bit keys (K1 - K16)
   self.final = []
   self.setKey(key)
 def setKey(self, key):
   """Will set the crypting key for this object. Must be 8 bytes."""
   _baseDes.setKey(self, key)
   self.__create_sub_keys()
 def __String_to_BitList(self, data):
   """Turn the string data, into a list of bits (1, 0)'s"""
   if _pythonMajorVersion < 3:
     # Turn the strings into integers. Python 3 uses a bytes
     # class, which already has this behaviour.
     data = [ord(c) for c in data]
   l = len(data) * 8
   result = [0] * l
   pos = 0
   for ch in data:
     i = 7
     while i >= 0:
       if ch & (1 << i) != 0:
         result[pos] = 1
       else:
         result[pos] = 0
       pos += 1
       i -= 1
   return result
 def __BitList_to_String(self, data):
   """Turn the list of bits -> data, into a string"""
   result = []
   pos = 0
   c = 0
   while pos < len(data):
     c += data[pos] << (7 - (pos ％ 8))
     if (pos ％ 8) == 7:
       result.append(c)
       c = 0
     pos += 1
   if _pythonMajorVersion < 3:
     return ''.join([ chr(c) for c in result ])
   else:
     return bytes(result)
 def __permutate(self, table, block):
   """Permutate this block with the specified table"""
   return list(map(lambda x: block[x], table))
 # Transform the secret key, so that it is ready for data processing
 # Create the 16 subkeys, K[1] - K[16]
 def __create_sub_keys(self):
   """Create the 16 subkeys K[1] to K[16] from the given key"""
   key = self.__permutate(des.__pc1, self.__String_to_BitList(self.getKey()))
   i = 0
   # Split into Left and Right sections
   self.L = key[:28]
   self.R = key[28:]
   while i < 16:
     j = 0
     # Perform circular left shifts
     while j < des.__left_rotations[i]:
       self.L.append(self.L[0])
       del self.L[0]
       self.R.append(self.R[0])
       del self.R[0]
       j += 1
     # Create one of the 16 subkeys through pc2 permutation
     self.Kn[i] = self.__permutate(des.__pc2, self.L + self.R)
     i += 1
 # Main part of the encryption algorithm, the number cruncher :)
 def __des_crypt(self, block, crypt_type):
   """Crypt the block of data through DES bit-manipulation"""
   block = self.__permutate(des.__ip, block)
   self.L = block[:32]
   self.R = block[32:]
   # Encryption starts from Kn[1] through to Kn[16]
   if crypt_type == des.ENCRYPT:
     iteration = 0
     iteration_adjustment = 1
   # Decryption starts from Kn[16] down to Kn[1]
   else:
     iteration = 15
     iteration_adjustment = -1
   i = 0
   while i < 16:
     # Make a copy of R[i-1], this will later become L[i]
     tempR = self.R[:]
     # Permutate R[i - 1] to start creating R[i]
     self.R = self.__permutate(des.__expansion_table, self.R)
     # Exclusive or R[i - 1] with K[i], create B[1] to B[8] whilst here
     self.R = list(map(lambda x, y: x ^ y, self.R, self.Kn[iteration]))
     B = [self.R[:6], self.R[6:12], self.R[12:18], self.R[18:24], self.R[24:30], self.R[30:36], self.R[36:42], self.R[42:]]
     # Optimization: Replaced below commented code with above
     #j = 0
     #B = []
     #while j < len(self.R):
     #  self.R[j] = self.R[j] ^ self.Kn[iteration][j]
     #  j += 1
     #  if j ％ 6 == 0:
     #    B.append(self.R[j-6:j])
     # Permutate B[1] to B[8] using the S-Boxes
     j = 0
     Bn = [0] * 32
     pos = 0
     while j < 8:
       # Work out the offsets
       m = (B[j][0] << 1) + B[j][5]
       n = (B[j][1] << 3) + (B[j][2] << 2) + (B[j][3] << 1) + B[j][4]
       # Find the permutation value
       v = des.__sbox[j][(m << 4) + n]
       # Turn value into bits, add it to result: Bn
       Bn[pos] = (v & 8) >> 3
       Bn[pos + 1] = (v & 4) >> 2
       Bn[pos + 2] = (v & 2) >> 1
       Bn[pos + 3] = v & 1
       pos += 4
       j += 1
     # Permutate the concatination of B[1] to B[8] (Bn)
     self.R = self.__permutate(des.__p, Bn)
     # Xor with L[i - 1]
     self.R = list(map(lambda x, y: x ^ y, self.R, self.L))
     # Optimization: This now replaces the below commented code
     #j = 0
     #while j < len(self.R):
     #  self.R[j] = self.R[j] ^ self.L[j]
     #  j += 1
     # L[i] becomes R[i - 1]
     self.L = tempR
     i += 1
     iteration += iteration_adjustment
   # Final permutation of R[16]L[16]
   self.final = self.__permutate(des.__fp, self.R + self.L)
   return self.final

# Data to be encrypted/decrypted
 def crypt(self, data, crypt_type):
   """Crypt the data in blocks, running it through des_crypt()"""
   # Error check the data
   if not data:
     return ''
   if len(data) ％ self.block_size != 0:
     if crypt_type == des.DECRYPT: # Decryption must work on 8 byte blocks
       raise ValueError("Invalid data length, data must be a multiple of " + str(self.block_size) + " bytes\n.")
     if not self.getPadding():
       raise ValueError("Invalid data length, data must be a multiple of " + str(self.block_size) + " bytes\n. Try setting the optional padding character")
     else:
       data += (self.block_size - (len(data) ％ self.block_size)) * self.getPadding()
     # print "Len of data: ％f" ％ (len(data) / self.block_size)
   if self.getMode() == CBC:
     if self.getIV():
       iv = self.__String_to_BitList(self.getIV())
     else:
       raise ValueError("For CBC mode, you must supply the Initial Value (IV) for ciphering")
   # Split the data into blocks, crypting each one seperately
   i = 0
   dict = {}
   result = []
   #cached = 0
   #lines = 0
   while i < len(data):
     # Test code for caching encryption results
     #lines += 1
     #if dict.has_key(data[i:i+8]):
       #print "Cached result for: ％s" ％ data[i:i+8]
     #  cached += 1
     #  result.append(dict[data[i:i+8]])
     #  i += 8
     #  continue
     block = self.__String_to_BitList(data[i:i+8])
     # Xor with IV if using CBC mode
     if self.getMode() == CBC:
       if crypt_type == des.ENCRYPT:
         block = list(map(lambda x, y: x ^ y, block, iv))
         #j = 0
         #while j < len(block):
         #  block[j] = block[j] ^ iv[j]
         #  j += 1
       processed_block = self.__des_crypt(block, crypt_type)
       if crypt_type == des.DECRYPT:
         processed_block = list(map(lambda x, y: x ^ y, processed_block, iv))
         #j = 0
         #while j < len(processed_block):
         #  processed_block[j] = processed_block[j] ^ iv[j]
         #  j += 1
         iv = block
       else:
         iv = processed_block
     else:
       processed_block = self.__des_crypt(block, crypt_type)

# Add the resulting crypted block to our list
     #d = self.__BitList_to_String(processed_block)
     #result.append(d)
     result.append(self.__BitList_to_String(processed_block))
     #dict[data[i:i+8]] = d
     i += 8
   # print "Lines: ％d, cached: ％d" ％ (lines, cached)
   # Return the full crypted string
   if _pythonMajorVersion < 3:
     return ''.join(result)
   else:
     return bytes.fromhex('').join(result)
 def encrypt(self, data, pad=None, padmode=None):
   """encrypt(data, [pad], [padmode]) -> bytes
   data : Bytes to be encrypted
   pad : Optional argument for encryption padding. Must only be one byte
   padmode : Optional argument for overriding the padding mode.
   The data must be a multiple of 8 bytes and will be encrypted
   with the already specified key. Data does not have to be a
   multiple of 8 bytes if the padding character is supplied, or
   the padmode is set to PAD_PKCS5, as bytes will then added to
   ensure the be padded data is a multiple of 8 bytes.
   """
   data = self._guardAgainstUnicode(data)
   if pad is not None:
     pad = self._guardAgainstUnicode(pad)
   data = self._padData(data, pad, padmode)
   return self.crypt(data, des.ENCRYPT)
 def decrypt(self, data, pad=None, padmode=None):
   """decrypt(data, [pad], [padmode]) -> bytes
   data : Bytes to be encrypted
   pad : Optional argument for decryption padding. Must only be one byte
   padmode : Optional argument for overriding the padding mode.
   The data must be a multiple of 8 bytes and will be decrypted
   with the already specified key. In PAD_NORMAL mode, if the
   optional padding character is supplied, then the un-encrypted
   data will have the padding characters removed from the end of
   the bytes. This pad removal only occurs on the last 8 bytes of
   the data (last data block). In PAD_PKCS5 mode, the special
   padding end markers will be removed from the data after decrypting.
   """
   data = self._guardAgainstUnicode(data)
   if pad is not None:
     pad = self._guardAgainstUnicode(pad)
   data = self.crypt(data, des.DECRYPT)
   return self._unpadData(data, pad, padmode)

#############################################################################
#         Triple DES          #
#############################################################################
class triple_des(_baseDes):
 """Triple DES encryption/decrytpion class
 This algorithm uses the DES-EDE3 (when a 24 byte key is supplied) or
 the DES-EDE2 (when a 16 byte key is supplied) encryption methods.
 Supports ECB (Electronic Code Book) and CBC (Cypher Block Chaining) modes.
 pyDes.des(key, [mode], [IV])
 key -> Bytes containing the encryption key, must be either 16 or
bytes long
 mode -> Optional argument for encryption type, can be either pyDes.ECB
   (Electronic Code Book), pyDes.CBC (Cypher Block Chaining)
 IV  -> Optional Initial Value bytes, must be supplied if using CBC mode.
   Must be 8 bytes in length.
 pad -> Optional argument, set the pad character (PAD_NORMAL) to use
   during all encrypt/decrpt operations done with this instance.
 padmode -> Optional argument, set the padding mode (PAD_NORMAL or
   PAD_PKCS5) to use during all encrypt/decrpt operations done
   with this instance.
 """
 def __init__(self, key, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL):
   _baseDes.__init__(self, mode, IV, pad, padmode)
   self.setKey(key)
 def setKey(self, key):
   """Will set the crypting key for this object. Either 16 or 24 bytes long."""
   self.key_size = 24 # Use DES-EDE3 mode
   if len(key) != self.key_size:
     if len(key) == 16: # Use DES-EDE2 mode
       self.key_size = 16
     else:
       raise ValueError("Invalid triple DES key size. Key must be either 16 or 24 bytes long")
   if self.getMode() == CBC:
     if not self.getIV():
       # Use the first 8 bytes of the key
       self._iv = key[:self.block_size]
     if len(self.getIV()) != self.block_size:
       raise ValueError("Invalid IV, must be 8 bytes in length")
   self.__key1 = des(key[:8], self._mode, self._iv,
        self._padding, self._padmode)
   self.__key2 = des(key[8:16], self._mode, self._iv,
        self._padding, self._padmode)
   if self.key_size == 16:
     self.__key3 = self.__key1
   else:
     self.__key3 = des(key[16:], self._mode, self._iv,
          self._padding, self._padmode)
   _baseDes.setKey(self, key)
 # Override setter methods to work on all 3 keys.
 def setMode(self, mode):
   """Sets the type of crypting mode, pyDes.ECB or pyDes.CBC"""
   _baseDes.setMode(self, mode)
   for key in (self.__key1, self.__key2, self.__key3):
     key.setMode(mode)
 def setPadding(self, pad):
   """setPadding() -> bytes of length 1. Padding character."""
   _baseDes.setPadding(self, pad)
   for key in (self.__key1, self.__key2, self.__key3):
     key.setPadding(pad)
 def setPadMode(self, mode):
   """Sets the type of padding mode, pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
   _baseDes.setPadMode(self, mode)
   for key in (self.__key1, self.__key2, self.__key3):
     key.setPadMode(mode)
 def setIV(self, IV):
   """Will set the Initial Value, used in conjunction with CBC mode"""
   _baseDes.setIV(self, IV)
   for key in (self.__key1, self.__key2, self.__key3):
     key.setIV(IV)
 def encrypt(self, data, pad=None, padmode=None):
   """encrypt(data, [pad], [padmode]) -> bytes
   data : bytes to be encrypted
   pad : Optional argument for encryption padding. Must only be one byte
   padmode : Optional argument for overriding the padding mode.
   The data must be a multiple of 8 bytes and will be encrypted
   with the already specified key. Data does not have to be a
   multiple of 8 bytes if the padding character is supplied, or
   the padmode is set to PAD_PKCS5, as bytes will then added to
   ensure the be padded data is a multiple of 8 bytes.
   """
   ENCRYPT = des.ENCRYPT
   DECRYPT = des.DECRYPT
   data = self._guardAgainstUnicode(data)
   if pad is not None:
     pad = self._guardAgainstUnicode(pad)
   # Pad the data accordingly.
   data = self._padData(data, pad, padmode)
   if self.getMode() == CBC:
     self.__key1.setIV(self.getIV())
     self.__key2.setIV(self.getIV())
     self.__key3.setIV(self.getIV())
     i = 0
     result = []
     while i < len(data):
       block = self.__key1.crypt(data[i:i+8], ENCRYPT)
       block = self.__key2.crypt(block, DECRYPT)
       block = self.__key3.crypt(block, ENCRYPT)
       self.__key1.setIV(block)
       self.__key2.setIV(block)
       self.__key3.setIV(block)
       result.append(block)
       i += 8
     if _pythonMajorVersion < 3:
       return ''.join(result)
     else:
       return bytes.fromhex('').join(result)
   else:
     data = self.__key1.crypt(data, ENCRYPT)
     data = self.__key2.crypt(data, DECRYPT)
     return self.__key3.crypt(data, ENCRYPT)
 def decrypt(self, data, pad=None, padmode=None):
   """decrypt(data, [pad], [padmode]) -> bytes
   data : bytes to be encrypted
   pad : Optional argument for decryption padding. Must only be one byte
   padmode : Optional argument for overriding the padding mode.
   The data must be a multiple of 8 bytes and will be decrypted
   with the already specified key. In PAD_NORMAL mode, if the
   optional padding character is supplied, then the un-encrypted
   data will have the padding characters removed from the end of
   the bytes. This pad removal only occurs on the last 8 bytes of
   the data (last data block). In PAD_PKCS5 mode, the special
   padding end markers will be removed from the data after
   decrypting, no pad character is required for PAD_PKCS5.
   """
   ENCRYPT = des.ENCRYPT
   DECRYPT = des.DECRYPT
   data = self._guardAgainstUnicode(data)
   if pad is not None:
     pad = self._guardAgainstUnicode(pad)
   if self.getMode() == CBC:
     self.__key1.setIV(self.getIV())
     self.__key2.setIV(self.getIV())
     self.__key3.setIV(self.getIV())
     i = 0
     result = []
     while i < len(data):
       iv = data[i:i+8]
       block = self.__key3.crypt(iv,  DECRYPT)
       block = self.__key2.crypt(block, ENCRYPT)
       block = self.__key1.crypt(block, DECRYPT)
       self.__key1.setIV(iv)
       self.__key2.setIV(iv)
       self.__key3.setIV(iv)
       result.append(block)
       i += 8
     if _pythonMajorVersion < 3:
       data = ''.join(result)
     else:
       data = bytes.fromhex('').join(result)
   else:
     data = self.__key3.crypt(data, DECRYPT)
     data = self.__key2.crypt(data, ENCRYPT)
     data = self.__key1.crypt(data, DECRYPT)
   return self._unpadData(data, pad, padmode)

希望本文所述对大家的Python程序设计有所帮助。