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572 lines
25 KiB
Python
572 lines
25 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Routines for doing AES CBC in one file
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Modified by some_updates to extract
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and combine only those parts needed for AES CBC
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into one simple to add python file
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Original Version
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Copyright (c) 2002 by Paul A. Lambert
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Under:
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CryptoPy Artisitic License Version 1.0
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See the wonderful pure python package cryptopy-1.2.5
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and read its LICENSE.txt for complete license details.
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Adjusted for Python 3, September 2020
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"""
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class CryptoError(Exception):
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""" Base class for crypto exceptions """
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def __init__(self,errorMessage='Error!'):
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self.message = errorMessage
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def __str__(self):
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return self.message
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class InitCryptoError(CryptoError):
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""" Crypto errors during algorithm initialization """
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class BadKeySizeError(InitCryptoError):
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""" Bad key size error """
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class EncryptError(CryptoError):
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""" Error in encryption processing """
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class DecryptError(CryptoError):
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""" Error in decryption processing """
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class DecryptNotBlockAlignedError(DecryptError):
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""" Error in decryption processing """
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def xorS(a,b):
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""" XOR two strings """
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assert len(a)==len(b)
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x = []
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for i in range(len(a)):
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x.append( chr(ord(a[i])^ord(b[i])))
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return ''.join(x)
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def xor(a,b):
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""" XOR two strings """
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x = []
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for i in range(min(len(a),len(b))):
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x.append( chr(ord(a[i])^ord(b[i])))
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return ''.join(x)
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"""
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Base 'BlockCipher' and Pad classes for cipher instances.
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BlockCipher supports automatic padding and type conversion. The BlockCipher
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class was written to make the actual algorithm code more readable and
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not for performance.
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"""
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class BlockCipher:
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""" Block ciphers """
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def __init__(self):
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self.reset()
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def reset(self):
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self.resetEncrypt()
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self.resetDecrypt()
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def resetEncrypt(self):
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self.encryptBlockCount = 0
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self.bytesToEncrypt = ''
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def resetDecrypt(self):
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self.decryptBlockCount = 0
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self.bytesToDecrypt = ''
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def encrypt(self, plainText, more = None):
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""" Encrypt a string and return a binary string """
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self.bytesToEncrypt += plainText # append plainText to any bytes from prior encrypt
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numBlocks, numExtraBytes = divmod(len(self.bytesToEncrypt), self.blockSize)
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cipherText = ''
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for i in range(numBlocks):
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bStart = i*self.blockSize
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ctBlock = self.encryptBlock(self.bytesToEncrypt[bStart:bStart+self.blockSize])
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self.encryptBlockCount += 1
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cipherText += ctBlock
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if numExtraBytes > 0: # save any bytes that are not block aligned
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self.bytesToEncrypt = self.bytesToEncrypt[-numExtraBytes:]
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else:
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self.bytesToEncrypt = ''
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if more == None: # no more data expected from caller
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finalBytes = self.padding.addPad(self.bytesToEncrypt,self.blockSize)
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if len(finalBytes) > 0:
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ctBlock = self.encryptBlock(finalBytes)
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self.encryptBlockCount += 1
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cipherText += ctBlock
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self.resetEncrypt()
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return cipherText
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def decrypt(self, cipherText, more = None):
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""" Decrypt a string and return a string """
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self.bytesToDecrypt += cipherText # append to any bytes from prior decrypt
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numBlocks, numExtraBytes = divmod(len(self.bytesToDecrypt), self.blockSize)
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if more == None: # no more calls to decrypt, should have all the data
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if numExtraBytes != 0:
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raise DecryptNotBlockAlignedError('Data not block aligned on decrypt')
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# hold back some bytes in case last decrypt has zero len
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if (more != None) and (numExtraBytes == 0) and (numBlocks >0) :
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numBlocks -= 1
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numExtraBytes = self.blockSize
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plainText = ''
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for i in range(numBlocks):
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bStart = i*self.blockSize
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ptBlock = self.decryptBlock(self.bytesToDecrypt[bStart : bStart+self.blockSize])
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self.decryptBlockCount += 1
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plainText += ptBlock
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if numExtraBytes > 0: # save any bytes that are not block aligned
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self.bytesToEncrypt = self.bytesToEncrypt[-numExtraBytes:]
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else:
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self.bytesToEncrypt = ''
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if more == None: # last decrypt remove padding
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plainText = self.padding.removePad(plainText, self.blockSize)
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self.resetDecrypt()
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return plainText
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class Pad:
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def __init__(self):
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pass # eventually could put in calculation of min and max size extension
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class padWithPadLen(Pad):
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""" Pad a binary string with the length of the padding """
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def addPad(self, extraBytes, blockSize):
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""" Add padding to a binary string to make it an even multiple
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of the block size """
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blocks, numExtraBytes = divmod(len(extraBytes), blockSize)
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padLength = blockSize - numExtraBytes
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return extraBytes + padLength*chr(padLength)
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def removePad(self, paddedBinaryString, blockSize):
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""" Remove padding from a binary string """
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if not(0<len(paddedBinaryString)):
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raise DecryptNotBlockAlignedError('Expected More Data')
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return paddedBinaryString[:-ord(paddedBinaryString[-1])]
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class noPadding(Pad):
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""" No padding. Use this to get ECB behavior from encrypt/decrypt """
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def addPad(self, extraBytes, blockSize):
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""" Add no padding """
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return extraBytes
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def removePad(self, paddedBinaryString, blockSize):
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""" Remove no padding """
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return paddedBinaryString
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"""
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Rijndael encryption algorithm
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This byte oriented implementation is intended to closely
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match FIPS specification for readability. It is not implemented
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for performance.
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"""
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class Rijndael(BlockCipher):
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""" Rijndael encryption algorithm """
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def __init__(self, key = None, padding = padWithPadLen(), keySize=16, blockSize=16 ):
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self.name = 'RIJNDAEL'
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self.keySize = keySize
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self.strength = keySize*8
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self.blockSize = blockSize # blockSize is in bytes
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self.padding = padding # change default to noPadding() to get normal ECB behavior
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assert( keySize%4==0 and keySize/4 in NrTable[4]),'key size must be 16,20,24,29 or 32 bytes'
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assert( blockSize%4==0 and blockSize/4 in NrTable), 'block size must be 16,20,24,29 or 32 bytes'
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self.Nb = self.blockSize/4 # Nb is number of columns of 32 bit words
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self.Nk = keySize/4 # Nk is the key length in 32-bit words
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self.Nr = NrTable[self.Nb][self.Nk] # The number of rounds (Nr) is a function of
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# the block (Nb) and key (Nk) sizes.
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if key != None:
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self.setKey(key)
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def setKey(self, key):
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""" Set a key and generate the expanded key """
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assert( len(key) == (self.Nk*4) ), 'Key length must be same as keySize parameter'
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self.__expandedKey = keyExpansion(self, key)
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self.reset() # BlockCipher.reset()
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def encryptBlock(self, plainTextBlock):
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""" Encrypt a block, plainTextBlock must be a array of bytes [Nb by 4] """
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self.state = self._toBlock(plainTextBlock)
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AddRoundKey(self, self.__expandedKey[0:self.Nb])
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for round in range(1,self.Nr): #for round = 1 step 1 to Nr
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SubBytes(self)
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ShiftRows(self)
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MixColumns(self)
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AddRoundKey(self, self.__expandedKey[round*self.Nb:(round+1)*self.Nb])
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SubBytes(self)
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ShiftRows(self)
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AddRoundKey(self, self.__expandedKey[self.Nr*self.Nb:(self.Nr+1)*self.Nb])
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return self._toBString(self.state)
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def decryptBlock(self, encryptedBlock):
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""" decrypt a block (array of bytes) """
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self.state = self._toBlock(encryptedBlock)
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AddRoundKey(self, self.__expandedKey[self.Nr*self.Nb:(self.Nr+1)*self.Nb])
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for round in range(self.Nr-1,0,-1):
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InvShiftRows(self)
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InvSubBytes(self)
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AddRoundKey(self, self.__expandedKey[round*self.Nb:(round+1)*self.Nb])
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InvMixColumns(self)
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InvShiftRows(self)
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InvSubBytes(self)
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AddRoundKey(self, self.__expandedKey[0:self.Nb])
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return self._toBString(self.state)
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def _toBlock(self, bs):
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""" Convert binary string to array of bytes, state[col][row]"""
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assert ( len(bs) == 4*self.Nb ), 'Rijndarl blocks must be of size blockSize'
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return [[ord(bs[4*i]),ord(bs[4*i+1]),ord(bs[4*i+2]),ord(bs[4*i+3])] for i in range(self.Nb)]
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def _toBString(self, block):
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""" Convert block (array of bytes) to binary string """
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l = []
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for col in block:
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for rowElement in col:
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l.append(chr(rowElement))
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return ''.join(l)
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#-------------------------------------
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""" Number of rounds Nr = NrTable[Nb][Nk]
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Nb Nk=4 Nk=5 Nk=6 Nk=7 Nk=8
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------------------------------------- """
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NrTable = {4: {4:10, 5:11, 6:12, 7:13, 8:14},
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5: {4:11, 5:11, 6:12, 7:13, 8:14},
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6: {4:12, 5:12, 6:12, 7:13, 8:14},
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7: {4:13, 5:13, 6:13, 7:13, 8:14},
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8: {4:14, 5:14, 6:14, 7:14, 8:14}}
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#-------------------------------------
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def keyExpansion(algInstance, keyString):
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""" Expand a string of size keySize into a larger array """
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Nk, Nb, Nr = algInstance.Nk, algInstance.Nb, algInstance.Nr # for readability
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key = [ord(byte) for byte in keyString] # convert string to list
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w = [[key[4*i],key[4*i+1],key[4*i+2],key[4*i+3]] for i in range(Nk)]
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for i in range(Nk,Nb*(Nr+1)):
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temp = w[i-1] # a four byte column
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if (i%Nk) == 0 :
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temp = temp[1:]+[temp[0]] # RotWord(temp)
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temp = [ Sbox[byte] for byte in temp ]
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temp[0] ^= Rcon[i/Nk]
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elif Nk > 6 and i%Nk == 4 :
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temp = [ Sbox[byte] for byte in temp ] # SubWord(temp)
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w.append( [ w[i-Nk][byte]^temp[byte] for byte in range(4) ] )
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return w
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Rcon = (0,0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36, # note extra '0' !!!
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0x6c,0xd8,0xab,0x4d,0x9a,0x2f,0x5e,0xbc,0x63,0xc6,
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0x97,0x35,0x6a,0xd4,0xb3,0x7d,0xfa,0xef,0xc5,0x91)
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#-------------------------------------
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def AddRoundKey(algInstance, keyBlock):
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""" XOR the algorithm state with a block of key material """
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for column in range(algInstance.Nb):
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for row in range(4):
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algInstance.state[column][row] ^= keyBlock[column][row]
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#-------------------------------------
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def SubBytes(algInstance):
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for column in range(algInstance.Nb):
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for row in range(4):
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algInstance.state[column][row] = Sbox[algInstance.state[column][row]]
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def InvSubBytes(algInstance):
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for column in range(algInstance.Nb):
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for row in range(4):
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algInstance.state[column][row] = InvSbox[algInstance.state[column][row]]
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Sbox = (0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,
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0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
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0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,
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0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
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0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,
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0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
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0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,
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0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
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0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,
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0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
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0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,
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0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
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0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,
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0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
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0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,
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0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
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0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,
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0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
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0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,
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0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
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0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,
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0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
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0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,
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0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
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0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,
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0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
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0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,
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0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
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0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,
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0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
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0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,
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0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16)
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InvSbox = (0x52,0x09,0x6a,0xd5,0x30,0x36,0xa5,0x38,
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0xbf,0x40,0xa3,0x9e,0x81,0xf3,0xd7,0xfb,
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0x7c,0xe3,0x39,0x82,0x9b,0x2f,0xff,0x87,
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0x34,0x8e,0x43,0x44,0xc4,0xde,0xe9,0xcb,
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0x54,0x7b,0x94,0x32,0xa6,0xc2,0x23,0x3d,
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0xee,0x4c,0x95,0x0b,0x42,0xfa,0xc3,0x4e,
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0x08,0x2e,0xa1,0x66,0x28,0xd9,0x24,0xb2,
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0x76,0x5b,0xa2,0x49,0x6d,0x8b,0xd1,0x25,
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0x72,0xf8,0xf6,0x64,0x86,0x68,0x98,0x16,
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0xd4,0xa4,0x5c,0xcc,0x5d,0x65,0xb6,0x92,
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0x6c,0x70,0x48,0x50,0xfd,0xed,0xb9,0xda,
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0x5e,0x15,0x46,0x57,0xa7,0x8d,0x9d,0x84,
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0x90,0xd8,0xab,0x00,0x8c,0xbc,0xd3,0x0a,
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0xf7,0xe4,0x58,0x05,0xb8,0xb3,0x45,0x06,
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0xd0,0x2c,0x1e,0x8f,0xca,0x3f,0x0f,0x02,
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0xc1,0xaf,0xbd,0x03,0x01,0x13,0x8a,0x6b,
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0x3a,0x91,0x11,0x41,0x4f,0x67,0xdc,0xea,
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0x97,0xf2,0xcf,0xce,0xf0,0xb4,0xe6,0x73,
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0x96,0xac,0x74,0x22,0xe7,0xad,0x35,0x85,
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0xe2,0xf9,0x37,0xe8,0x1c,0x75,0xdf,0x6e,
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0x47,0xf1,0x1a,0x71,0x1d,0x29,0xc5,0x89,
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0x6f,0xb7,0x62,0x0e,0xaa,0x18,0xbe,0x1b,
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0xfc,0x56,0x3e,0x4b,0xc6,0xd2,0x79,0x20,
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0x9a,0xdb,0xc0,0xfe,0x78,0xcd,0x5a,0xf4,
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0x1f,0xdd,0xa8,0x33,0x88,0x07,0xc7,0x31,
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0xb1,0x12,0x10,0x59,0x27,0x80,0xec,0x5f,
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0x60,0x51,0x7f,0xa9,0x19,0xb5,0x4a,0x0d,
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0x2d,0xe5,0x7a,0x9f,0x93,0xc9,0x9c,0xef,
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0xa0,0xe0,0x3b,0x4d,0xae,0x2a,0xf5,0xb0,
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0xc8,0xeb,0xbb,0x3c,0x83,0x53,0x99,0x61,
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0x17,0x2b,0x04,0x7e,0xba,0x77,0xd6,0x26,
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0xe1,0x69,0x14,0x63,0x55,0x21,0x0c,0x7d)
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#-------------------------------------
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""" For each block size (Nb), the ShiftRow operation shifts row i
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by the amount Ci. Note that row 0 is not shifted.
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Nb C1 C2 C3
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------------------- """
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shiftOffset = { 4 : ( 0, 1, 2, 3),
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5 : ( 0, 1, 2, 3),
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6 : ( 0, 1, 2, 3),
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7 : ( 0, 1, 2, 4),
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8 : ( 0, 1, 3, 4) }
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def ShiftRows(algInstance):
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tmp = [0]*algInstance.Nb # list of size Nb
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for r in range(1,4): # row 0 reamains unchanged and can be skipped
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for c in range(algInstance.Nb):
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tmp[c] = algInstance.state[(c+shiftOffset[algInstance.Nb][r]) % algInstance.Nb][r]
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for c in range(algInstance.Nb):
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algInstance.state[c][r] = tmp[c]
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def InvShiftRows(algInstance):
|
|
tmp = [0]*algInstance.Nb # list of size Nb
|
|
for r in range(1,4): # row 0 reamains unchanged and can be skipped
|
|
for c in range(algInstance.Nb):
|
|
tmp[c] = algInstance.state[(c+algInstance.Nb-shiftOffset[algInstance.Nb][r]) % algInstance.Nb][r]
|
|
for c in range(algInstance.Nb):
|
|
algInstance.state[c][r] = tmp[c]
|
|
#-------------------------------------
|
|
def MixColumns(a):
|
|
Sprime = [0,0,0,0]
|
|
for j in range(a.Nb): # for each column
|
|
Sprime[0] = mul(2,a.state[j][0])^mul(3,a.state[j][1])^mul(1,a.state[j][2])^mul(1,a.state[j][3])
|
|
Sprime[1] = mul(1,a.state[j][0])^mul(2,a.state[j][1])^mul(3,a.state[j][2])^mul(1,a.state[j][3])
|
|
Sprime[2] = mul(1,a.state[j][0])^mul(1,a.state[j][1])^mul(2,a.state[j][2])^mul(3,a.state[j][3])
|
|
Sprime[3] = mul(3,a.state[j][0])^mul(1,a.state[j][1])^mul(1,a.state[j][2])^mul(2,a.state[j][3])
|
|
for i in range(4):
|
|
a.state[j][i] = Sprime[i]
|
|
|
|
def InvMixColumns(a):
|
|
""" Mix the four bytes of every column in a linear way
|
|
This is the opposite operation of Mixcolumn """
|
|
Sprime = [0,0,0,0]
|
|
for j in range(a.Nb): # for each column
|
|
Sprime[0] = mul(0x0E,a.state[j][0])^mul(0x0B,a.state[j][1])^mul(0x0D,a.state[j][2])^mul(0x09,a.state[j][3])
|
|
Sprime[1] = mul(0x09,a.state[j][0])^mul(0x0E,a.state[j][1])^mul(0x0B,a.state[j][2])^mul(0x0D,a.state[j][3])
|
|
Sprime[2] = mul(0x0D,a.state[j][0])^mul(0x09,a.state[j][1])^mul(0x0E,a.state[j][2])^mul(0x0B,a.state[j][3])
|
|
Sprime[3] = mul(0x0B,a.state[j][0])^mul(0x0D,a.state[j][1])^mul(0x09,a.state[j][2])^mul(0x0E,a.state[j][3])
|
|
for i in range(4):
|
|
a.state[j][i] = Sprime[i]
|
|
|
|
#-------------------------------------
|
|
def mul(a, b):
|
|
""" Multiply two elements of GF(2^m)
|
|
needed for MixColumn and InvMixColumn """
|
|
if (a !=0 and b!=0):
|
|
return Alogtable[(Logtable[a] + Logtable[b])%255]
|
|
else:
|
|
return 0
|
|
|
|
Logtable = ( 0, 0, 25, 1, 50, 2, 26, 198, 75, 199, 27, 104, 51, 238, 223, 3,
|
|
100, 4, 224, 14, 52, 141, 129, 239, 76, 113, 8, 200, 248, 105, 28, 193,
|
|
125, 194, 29, 181, 249, 185, 39, 106, 77, 228, 166, 114, 154, 201, 9, 120,
|
|
101, 47, 138, 5, 33, 15, 225, 36, 18, 240, 130, 69, 53, 147, 218, 142,
|
|
150, 143, 219, 189, 54, 208, 206, 148, 19, 92, 210, 241, 64, 70, 131, 56,
|
|
102, 221, 253, 48, 191, 6, 139, 98, 179, 37, 226, 152, 34, 136, 145, 16,
|
|
126, 110, 72, 195, 163, 182, 30, 66, 58, 107, 40, 84, 250, 133, 61, 186,
|
|
43, 121, 10, 21, 155, 159, 94, 202, 78, 212, 172, 229, 243, 115, 167, 87,
|
|
175, 88, 168, 80, 244, 234, 214, 116, 79, 174, 233, 213, 231, 230, 173, 232,
|
|
44, 215, 117, 122, 235, 22, 11, 245, 89, 203, 95, 176, 156, 169, 81, 160,
|
|
127, 12, 246, 111, 23, 196, 73, 236, 216, 67, 31, 45, 164, 118, 123, 183,
|
|
204, 187, 62, 90, 251, 96, 177, 134, 59, 82, 161, 108, 170, 85, 41, 157,
|
|
151, 178, 135, 144, 97, 190, 220, 252, 188, 149, 207, 205, 55, 63, 91, 209,
|
|
83, 57, 132, 60, 65, 162, 109, 71, 20, 42, 158, 93, 86, 242, 211, 171,
|
|
68, 17, 146, 217, 35, 32, 46, 137, 180, 124, 184, 38, 119, 153, 227, 165,
|
|
103, 74, 237, 222, 197, 49, 254, 24, 13, 99, 140, 128, 192, 247, 112, 7)
|
|
|
|
Alogtable= ( 1, 3, 5, 15, 17, 51, 85, 255, 26, 46, 114, 150, 161, 248, 19, 53,
|
|
95, 225, 56, 72, 216, 115, 149, 164, 247, 2, 6, 10, 30, 34, 102, 170,
|
|
229, 52, 92, 228, 55, 89, 235, 38, 106, 190, 217, 112, 144, 171, 230, 49,
|
|
83, 245, 4, 12, 20, 60, 68, 204, 79, 209, 104, 184, 211, 110, 178, 205,
|
|
76, 212, 103, 169, 224, 59, 77, 215, 98, 166, 241, 8, 24, 40, 120, 136,
|
|
131, 158, 185, 208, 107, 189, 220, 127, 129, 152, 179, 206, 73, 219, 118, 154,
|
|
181, 196, 87, 249, 16, 48, 80, 240, 11, 29, 39, 105, 187, 214, 97, 163,
|
|
254, 25, 43, 125, 135, 146, 173, 236, 47, 113, 147, 174, 233, 32, 96, 160,
|
|
251, 22, 58, 78, 210, 109, 183, 194, 93, 231, 50, 86, 250, 21, 63, 65,
|
|
195, 94, 226, 61, 71, 201, 64, 192, 91, 237, 44, 116, 156, 191, 218, 117,
|
|
159, 186, 213, 100, 172, 239, 42, 126, 130, 157, 188, 223, 122, 142, 137, 128,
|
|
155, 182, 193, 88, 232, 35, 101, 175, 234, 37, 111, 177, 200, 67, 197, 84,
|
|
252, 31, 33, 99, 165, 244, 7, 9, 27, 45, 119, 153, 176, 203, 70, 202,
|
|
69, 207, 74, 222, 121, 139, 134, 145, 168, 227, 62, 66, 198, 81, 243, 14,
|
|
18, 54, 90, 238, 41, 123, 141, 140, 143, 138, 133, 148, 167, 242, 13, 23,
|
|
57, 75, 221, 124, 132, 151, 162, 253, 28, 36, 108, 180, 199, 82, 246, 1)
|
|
|
|
|
|
|
|
|
|
"""
|
|
AES Encryption Algorithm
|
|
The AES algorithm is just Rijndael algorithm restricted to the default
|
|
blockSize of 128 bits.
|
|
"""
|
|
|
|
class AES(Rijndael):
|
|
""" The AES algorithm is the Rijndael block cipher restricted to block
|
|
sizes of 128 bits and key sizes of 128, 192 or 256 bits
|
|
"""
|
|
def __init__(self, key = None, padding = padWithPadLen(), keySize=16):
|
|
""" Initialize AES, keySize is in bytes """
|
|
if not (keySize == 16 or keySize == 24 or keySize == 32) :
|
|
raise BadKeySizeError('Illegal AES key size, must be 16, 24, or 32 bytes')
|
|
|
|
Rijndael.__init__( self, key, padding=padding, keySize=keySize, blockSize=16 )
|
|
|
|
self.name = 'AES'
|
|
|
|
|
|
"""
|
|
CBC mode of encryption for block ciphers.
|
|
This algorithm mode wraps any BlockCipher to make a
|
|
Cipher Block Chaining mode.
|
|
"""
|
|
from random import Random # should change to crypto.random!!!
|
|
|
|
|
|
class CBC(BlockCipher):
|
|
""" The CBC class wraps block ciphers to make cipher block chaining (CBC) mode
|
|
algorithms. The initialization (IV) is automatic if set to None. Padding
|
|
is also automatic based on the Pad class used to initialize the algorithm
|
|
"""
|
|
def __init__(self, blockCipherInstance, padding = padWithPadLen()):
|
|
""" CBC algorithms are created by initializing with a BlockCipher instance """
|
|
self.baseCipher = blockCipherInstance
|
|
self.name = self.baseCipher.name + '_CBC'
|
|
self.blockSize = self.baseCipher.blockSize
|
|
self.keySize = self.baseCipher.keySize
|
|
self.padding = padding
|
|
self.baseCipher.padding = noPadding() # baseCipher should NOT pad!!
|
|
self.r = Random() # for IV generation, currently uses
|
|
# mediocre standard distro version <----------------
|
|
import time
|
|
newSeed = time.ctime()+str(self.r) # seed with instance location
|
|
self.r.seed(newSeed) # to make unique
|
|
self.reset()
|
|
|
|
def setKey(self, key):
|
|
self.baseCipher.setKey(key)
|
|
|
|
# Overload to reset both CBC state and the wrapped baseCipher
|
|
def resetEncrypt(self):
|
|
BlockCipher.resetEncrypt(self) # reset CBC encrypt state (super class)
|
|
self.baseCipher.resetEncrypt() # reset base cipher encrypt state
|
|
|
|
def resetDecrypt(self):
|
|
BlockCipher.resetDecrypt(self) # reset CBC state (super class)
|
|
self.baseCipher.resetDecrypt() # reset base cipher decrypt state
|
|
|
|
def encrypt(self, plainText, iv=None, more=None):
|
|
""" CBC encryption - overloads baseCipher to allow optional explicit IV
|
|
when iv=None, iv is auto generated!
|
|
"""
|
|
if self.encryptBlockCount == 0:
|
|
self.iv = iv
|
|
else:
|
|
assert(iv==None), 'IV used only on first call to encrypt'
|
|
|
|
return BlockCipher.encrypt(self,plainText, more=more)
|
|
|
|
def decrypt(self, cipherText, iv=None, more=None):
|
|
""" CBC decryption - overloads baseCipher to allow optional explicit IV
|
|
when iv=None, iv is auto generated!
|
|
"""
|
|
if self.decryptBlockCount == 0:
|
|
self.iv = iv
|
|
else:
|
|
assert(iv==None), 'IV used only on first call to decrypt'
|
|
|
|
return BlockCipher.decrypt(self, cipherText, more=more)
|
|
|
|
def encryptBlock(self, plainTextBlock):
|
|
""" CBC block encryption, IV is set with 'encrypt' """
|
|
auto_IV = ''
|
|
if self.encryptBlockCount == 0:
|
|
if self.iv == None:
|
|
# generate IV and use
|
|
self.iv = ''.join([chr(self.r.randrange(256)) for i in range(self.blockSize)])
|
|
self.prior_encr_CT_block = self.iv
|
|
auto_IV = self.prior_encr_CT_block # prepend IV if it's automatic
|
|
else: # application provided IV
|
|
assert(len(self.iv) == self.blockSize ),'IV must be same length as block'
|
|
self.prior_encr_CT_block = self.iv
|
|
""" encrypt the prior CT XORed with the PT """
|
|
ct = self.baseCipher.encryptBlock( xor(self.prior_encr_CT_block, plainTextBlock) )
|
|
self.prior_encr_CT_block = ct
|
|
return auto_IV+ct
|
|
|
|
def decryptBlock(self, encryptedBlock):
|
|
""" Decrypt a single block """
|
|
|
|
if self.decryptBlockCount == 0: # first call, process IV
|
|
if self.iv == None: # auto decrypt IV?
|
|
self.prior_CT_block = encryptedBlock
|
|
return ''
|
|
else:
|
|
assert(len(self.iv)==self.blockSize),"Bad IV size on CBC decryption"
|
|
self.prior_CT_block = self.iv
|
|
|
|
dct = self.baseCipher.decryptBlock(encryptedBlock)
|
|
""" XOR the prior decrypted CT with the prior CT """
|
|
dct_XOR_priorCT = xor( self.prior_CT_block, dct )
|
|
|
|
self.prior_CT_block = encryptedBlock
|
|
|
|
return dct_XOR_priorCT
|
|
|
|
|
|
"""
|
|
AES_CBC Encryption Algorithm
|
|
"""
|
|
|
|
class AES_CBC(CBC):
|
|
""" AES encryption in CBC feedback mode """
|
|
def __init__(self, key=None, padding=padWithPadLen(), keySize=16):
|
|
CBC.__init__( self, AES(key, noPadding(), keySize), padding)
|
|
self.name = 'AES_CBC'
|