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/' target='_blank'>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 DESmode  -> 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 anypadding issues, as the padding can be removed unambiguously upon decryptingdata that was encrypted using PAD_PKCS5 padmode.Common methods--------------encrypt(data, [pad], [padmode])decrypt(data, [pad], [padmode])data  -> Bytes to be encrypted/decryptedpad   -> 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" % dprint "Decrypted: %r" % k.decrypt(d)assert k.decrypt(d, padmode=PAD_PKCS5) == dataSee 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 / cypheringECB =  0CBC =  1# Modes of paddingPAD_NORMAL = 1PAD_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)

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