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。