pyDes.py源码
#############################################################################
# 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, " ", 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" ", 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,
0, 57, 49, 41, 33, 25, 17,
9, 1, 58, 50, 42, 34, 26,
18, 10, 2, 59, 51, 43, 35,
62, 54, 46, 38, 30, 22, 14,
6, 61, 53, 45, 37, 29, 21,
13, 5, 60, 52, 44, 36, 28,
20, 12, 4, 27, 19, 11, 3
]
# number left rotations of pc1
__left_rotations = [
1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
]
# permuted choice key (table 2)
__pc2 = [
13, 16, 10, 23, 0, 4,
2, 27, 14, 5, 20, 9,
22, 18, 11, 3, 25, 7,
15, 6, 26, 19, 12, 1,
40, 51, 30, 36, 46, 54,
29, 39, 50, 44, 32, 47,
43, 48, 38, 55, 33, 52,
45, 41, 49, 35, 28, 31
]
# initial permutation IP
__ip = [57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7,
56, 48, 40, 32, 24, 16, 8, 0,
58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6
]
# Expansion table for turning 32 bit blocks into 48 bits
__expansion_table = [
31, 0, 1, 2, 3, 4,
3, 4, 5, 6, 7, 8,
7, 8, 9, 10, 11, 12,
11, 12, 13, 14, 15, 16,
15, 16, 17, 18, 19, 20,
19, 20, 21, 22, 23, 24,
23, 24, 25, 26, 27, 28,
27, 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,
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 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,
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 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,
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 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,
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 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,
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 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,
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 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,
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 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,
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 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 = [
15, 6, 19, 20, 28, 11,
27, 16, 0, 14, 22, 25,
4, 17, 30, 9, 1, 7,
23,13, 31, 26, 2, 8,
18, 12, 29, 5, 21, 10,
3, 24
]
# final permutation IP^-1
__fp = [
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25,
32, 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
.")
if not self.getPadding():
raise ValueError("Invalid data length, data must be a multiple of " + str(self.block_size) + " bytes
. 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)