#!/usr/bin/env python3 # aes.py: implements AES - Advanced Encryption Standard # from the SlowAES project, http://code.google.com/p/slowaes/ # # Copyright (c) 2008 Josh Davis ( http://www.josh-davis.org ), Alex Martelli ( http://www.aleax.it ) # # Ported from C code written by Laurent Haan ( http://www.progressive-coding.com ) # Licensed under the Apache License, Version 2.0 # http://www.apache.org/licenses/ # """ Ported to Python3 with minimal changements. © Copyright 2018 Matteo ℱan """ import os import math def append_PKCS7_padding(val): """ Function to pad the given data to a multiple of 16-bytes by PKCS7 padding. """ numpads = 16 - (len(val) % 16) return val + numpads * bytes(chr(numpads), 'utf-8') def strip_PKCS7_padding(val): """ Function to strip off PKCS7 padding. """ if len(val) % 16 or not val: raise ValueError("String of len %d can't be PCKS7-padded" % len(val)) numpads = val[-1] if numpads > 16: raise ValueError("String ending with %r can't be PCKS7-padded" % val[-1]) return val[:-numpads] class AES( object ): """ Class implementing the Advanced Encryption Standard algorithm. """ #*py-kms* v6 = False # Valid key sizes KeySize = { "SIZE_128": 16, "SIZE_192": 24, "SIZE_256": 32 } # Rijndael S-box sbox = [ 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 ] # Rijndael Inverted S-box rsbox = [ 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d ] # Rijndael Rcon Rcon = [ 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb ] def getSBoxValue(self,num): """ Method to retrieve a given S-Box value. """ return self.sbox[num] def getSBoxInvert(self,num): """ Method to retrieve a given Inverted S-Box value.""" return self.rsbox[num] def rotate(self, word): """ Method performing Rijndael's key schedule rotate operation. Rotate a word eight bits to the left: eg, rotate(1d2c3a4f) == 2c3a4f1d @param word: char list of size 4 (32 bits overall). """ return word[1:] + word[:1] def getRconValue(self, num): """ Method to retrieve a given Rcon value. """ return self.Rcon[num] def core(self, word, iteration): """ Method performing the key schedule core operation. """ # Rotate the 32-bit word 8 bits to the left. word = self.rotate(word) # Apply S-Box substitution on all 4 parts of the 32-bit word. for i in range(4): word[i] = self.getSBoxValue(word[i]) # XOR the output of the rcon operation with i to the first part (leftmost) only. word[0] = word[0] ^ self.getRconValue(iteration) return word def expandKey(self, key, size, expandedKeySize): """ Method performing Rijndael's key expansion. Expands an 128, 192, 256 key into an 176, 208, 240 bit key. """ # Current expanded keySize, in bytes. currentSize = 0 rconIteration = 1 expandedKey = [0] * expandedKeySize # Set the 16, 24, 32 bytes of the expanded key to the input key. for j in range(size): expandedKey[j] = key[j] currentSize += size while currentSize < expandedKeySize: # Assign the previous 4 bytes to the temporary value t. t = expandedKey[currentSize - 4:currentSize] # Every 16,24,32 bytes we apply the core schedule to t # and increment rconIteration afterwards. if currentSize % size == 0: t = self.core(t, rconIteration) rconIteration += 1 # For 256-bit keys, we add an extra sbox to the calculation. if size == self.KeySize["SIZE_256"] and ((currentSize % size) == 16): for l in range(4): t[l] = self.getSBoxValue(t[l]) # We XOR t with the four-byte block 16,24,32 bytes before the new # expanded key. This becomes the next four bytes in the expanded key. for m in range(4): expandedKey[currentSize] = expandedKey[currentSize - size] ^ t[m] currentSize += 1 return expandedKey def addRoundKey(self, state, roundKey): """ Method to add (XORs) the round key to the state. """ for i in range(16): state[i] ^= roundKey[i] return state def createRoundKey(self, expandedKey, roundKeyPointer): """ Creates a round key from the given expanded key and the position within the expanded key. """ roundKey = [0] * 16 for i in range(4): for j in range(4): roundKey[j * 4 + i] = expandedKey[roundKeyPointer + i * 4 + j] return roundKey def galois_multiplication(self, a, b): """ Method to perform a Galois multiplication of 8 bit characters a and b. """ p = 0 for counter in range(8): if b & 1: p ^= a hi_bit_set = a & 0x80 a <<= 1 # keep a 8 bit a &= 0xFF if hi_bit_set: a ^= 0x1b b >>= 1 return p def subBytes(self, state, isInv): """ Method to substitute all the values from the state with the value in the SBox using the state value as index for the SBox. """ if isInv: getter = self.getSBoxInvert else: getter = self.getSBoxValue for i in range(16): state[i] = getter(state[i]) return state def shiftRows(self, state, isInv): """ Method to iterate over the 4 rows and call shiftRow(...) with that row. """ for i in range(4): state = self.shiftRow(state, i * 4, i, isInv) return state def shiftRow(self, state, statePointer, nbr, isInv): """ Method to shift the row to the left. """ for i in range(nbr): if isInv: state[statePointer:statePointer + 4] = state[statePointer + 3:statePointer + 4] + \ state[statePointer:statePointer + 3] else: state[statePointer:statePointer + 4] = state[statePointer + 1:statePointer + 4] + \ state[statePointer:statePointer + 1] return state def mixColumns(self, state, isInv): """ Method to perform a galois multiplication of the 4x4 matrix. """ # Iterate over the 4 columns. for i in range(4): # Construct one column by slicing over the 4 rows. column = state[i:i + 16:4] # Apply the mixColumn on one column. column = self.mixColumn(column, isInv) # Put the values back into the state. state[i:i + 16:4] = column return state def mixColumn(self, column, isInv): """ Method to perform a galois multiplication of 1 column the 4x4 matrix. """ if isInv: mult = [14, 9, 13, 11] else: mult = [2, 1, 1, 3] cpy = list(column) g = self.galois_multiplication column[0] = g(cpy[0], mult[0]) ^ g(cpy[3], mult[1]) ^ \ g(cpy[2], mult[2]) ^ g(cpy[1], mult[3]) column[1] = g(cpy[1], mult[0]) ^ g(cpy[0], mult[1]) ^ \ g(cpy[3], mult[2]) ^ g(cpy[2], mult[3]) column[2] = g(cpy[2], mult[0]) ^ g(cpy[1], mult[1]) ^ \ g(cpy[0], mult[2]) ^ g(cpy[3], mult[3]) column[3] = g(cpy[3], mult[0]) ^ g(cpy[2], mult[1]) ^ \ g(cpy[1], mult[2]) ^ g(cpy[0], mult[3]) return column def aes_round(self, state, roundKey, roundKms): """ Method to apply the 4 operations of the forward round in sequence. """ state = self.subBytes(state, False) state = self.shiftRows(state, False) state = self.mixColumns(state, False) #*py-kms* if self.v6: if roundKms == 4: state[0] ^= 0x73 if roundKms == 6: state[0] ^= 0x09 if roundKms == 8: state[0] ^= 0xE4 state = self.addRoundKey(state, roundKey) return state def aes_invRound(self, state, roundKey, roundKms): """ Method to apply the 4 operations of the inverse round in sequence. """ state = self.shiftRows(state, True) state = self.subBytes(state, True) state = self.addRoundKey(state, roundKey) #*py-kms* if self.v6: if roundKms == 4: state[0] ^= 0x73 if roundKms == 6: state[0] ^= 0x09 if roundKms == 8: state[0] ^= 0xE4 state = self.mixColumns(state, True) return state def aes_main(self, state, expandedKey, nbrRounds): """ Method to do the AES encryption for one round. Perform the initial operations, the standard round and the final operations of the forward AES, creating a round key for each round. """ state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0)) i = 1 while i < nbrRounds: state = self.aes_round(state, self.createRoundKey(expandedKey, 16 * i), i) i += 1 state = self.subBytes(state, False) state = self.shiftRows(state, False) state = self.addRoundKey(state, self.createRoundKey(expandedKey, 16 * nbrRounds)) return state def aes_invMain(self, state, expandedKey, nbrRounds): """ Method to do the inverse AES encryption for one round. Perform the initial operations, the standard round, and the final operations of the inverse AES, creating a round key for each round. """ state = self.addRoundKey(state, self.createRoundKey(expandedKey, 16 * nbrRounds)) i = nbrRounds - 1 while i > 0: state = self.aes_invRound(state, self.createRoundKey(expandedKey, 16 * i), i) i -= 1 state = self.shiftRows(state, True) state = self.subBytes(state, True) state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0)) return state def encrypt(self, iput, key, size): """ Method to encrypt a 128 bit input block against the given key of size specified. """ output = [0] * 16 # The number of rounds. nbrRounds = 0 # The 128 bit block to encode. block = [0] * 16 # Set the number of rounds. if size == self.KeySize["SIZE_128"]: nbrRounds = 10 elif size == self.KeySize["SIZE_192"]: nbrRounds = 12 elif size == self.KeySize["SIZE_256"]: nbrRounds = 14 # *py-kms* The KMS v4 parameters. elif size == 20: nbrRounds = 11 else: raise ValueError("Wrong key size given ({}).".format(size)) # The expanded keySize. expandedKeySize = 16 * (nbrRounds + 1) # Set the block values, for the block: # a[0,0] a[0,1] a[0,2] a[0,3] # a[1,0] a[1,1] a[1,2] a[1,3] # a[2,0] a[2,1] a[2,2] a[2,3] # a[3,0] a[3,1] a[3,2] a[3,3] # the mapping order is a[0,0] a[1,0] a[2,0] a[3,0] a[0,1] a[1,1] ... a[2,3] a[3,3] # Iterate over the columns and over the rows. for i in range(4): for j in range(4): block[i + j * 4] = iput[i * 4 +j] # Expand the key into an 176, 208, 240 bit key expandedKey = self.expandKey(key, size, expandedKeySize) # Encrypt the block using the expandedKey. block = self.aes_main(block, expandedKey, nbrRounds) # Unmap the block again into the output. for k in range(4): for l in range(4): output[k * 4 + l] = block[k + l * 4] return output def decrypt(self, iput, key, size): """ Method to decrypt a 128 bit input block against the given key of size specified. """ output = [0] * 16 # The number of rounds. nbrRounds = 0 # The 128 bit block to decode. block = [0] * 16 # Set the number of rounds. if size == self.KeySize["SIZE_128"]: nbrRounds = 10 elif size == self.KeySize["SIZE_192"]: nbrRounds = 12 elif size == self.KeySize["SIZE_256"]: nbrRounds = 14 #*py-kms* The KMS v4 parameters. elif size == 20: nbrRounds = 11 else: raise ValueError("Wrong key size given ({}).".format(size)) # The expanded keySize. expandedKeySize = 16 * (nbrRounds + 1) # Set the block values, for the block: # a[0,0] a[0,1] a[0,2] a[0,3] # a[1,0] a[1,1] a[1,2] a[1,3] # a[2,0] a[2,1] a[2,2] a[2,3] # a[3,0] a[3,1] a[3,2] a[3,3] # the mapping order is a[0,0] a[1,0] a[2,0] a[3,0] a[0,1] a[1,1] ... a[2,3] a[3,3] # Iterate over the columns and the rows. for i in range(4): for j in range(4): block[i + j * 4] = iput[i * 4 + j] # Expand the key into an 176, 208, 240 bit key. expandedKey = self.expandKey(key, size, expandedKeySize) # Decrypt the block using the expandedKey. block = self.aes_invMain(block, expandedKey, nbrRounds) # Unmap the block again into the output. for k in range(4): for l in range(4): output[k * 4 +l] = block[k + l * 4] return output class AESModeOfOperation( object ): """ Class implementing the different AES mode of operations. """ aes = AES() # Supported modes of operation. ModeOfOperation = { "OFB": 0, "CFB": 1, "CBC": 2 } def convertString(self, string, start, end, mode): """ Method to convert a 16 character string into a number array. """ if end - start > 16: end = start + 16 if mode == self.ModeOfOperation["CBC"]: ar = [0] * 16 else: ar = [] i = start j = 0 while len(ar) < end - start: ar.append(0) while i < end: ar[j] = string[i] j += 1 i += 1 return ar def encrypt(self, stringIn, mode, key, size, IV): """ Method to perform the encryption operation. @param stringIn: input string to be encrypted @param mode: mode of operation (0, 1 or 2) @param key: a hex key of the bit length size @param size: the bit length of the key (16, 24 or 32) @param IV: the 128 bit hex initilization vector @return tuple with mode of operation, length of the input and the encrypted data """ if len(key) % size: raise ValueError("Illegal size ({}) for key '{}'.".format(size, key)) if len(IV) % 16: raise ValueError("IV is not a multiple of 16.") # The AES input/output. plaintext = [] iput = [0] * 16 output = [] ciphertext = [0] * 16 # The output cipher string. cipherOut = [] firstRound = True if stringIn != None: for j in range(int(math.ceil(float(len(stringIn))/16))): start = j * 16 end = j * 16 + 16 if end > len(stringIn): end = len(stringIn) plaintext = self.convertString(stringIn, start, end, mode) if mode == self.ModeOfOperation["CFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(plaintext) - 1 < i: ciphertext[i] = 0 ^ output[i] elif len(output) - 1 < i: ciphertext[i] = plaintext[i] ^ 0 elif len(plaintext) - 1 < i and len(output) < i: ciphertext[i] = 0 ^ 0 else: ciphertext[i] = plaintext[i] ^ output[i] for k in range(end - start): cipherOut.append(ciphertext[k]) iput = ciphertext elif mode == self.ModeOfOperation["OFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(plaintext) - 1 < i: ciphertext[i] = 0 ^ output[i] elif len(output) - 1 < i: ciphertext[i] = plaintext[i] ^ 0 elif len(plaintext) - 1 < i and len(output) < i: ciphertext[i] = 0 ^ 0 else: ciphertext[i] = plaintext[i] ^ output[i] for k in range(end - start): cipherOut.append(ciphertext[k]) iput = output elif mode == self.ModeOfOperation["CBC"]: for i in range(16): if firstRound: iput[i] = plaintext[i] ^ IV[i] else: iput[i] = plaintext[i] ^ ciphertext[i] firstRound = False ciphertext = self.aes.encrypt(iput, key, size) # Always 16 bytes because of the padding for CBC. for k in range(16): cipherOut.append(ciphertext[k]) return mode, len(stringIn), cipherOut def decrypt(self, cipherIn, originalsize, mode, key, size, IV): """ Method to perform the decryption operation. @param cipherIn: encrypted string to be decrypted @param originalsize: unencrypted string length (required for CBC) @param mode: mode of operation (0, 1 or 2) @param key: a number array of the bit length size @param size: the bit length of the key (16, 24 or 32) @param IV: the 128 bit number array initilization vector @return decrypted data """ if len(key) % size: raise ValueError("Illegal size ({}) for key '{}'.".format(size, key)) if len(IV) % 16: raise ValueError("IV is not a multiple of 16.") # The AES input/output. ciphertext = [] iput = [] output = [] plaintext = [0] * 16 # The output plain text character list. chrOut = [] firstRound = True if cipherIn != None: for j in range(int(math.ceil(float(len(cipherIn))/16))): start = j * 16 end = j * 16 + 16 if j * 16 + 16 > len(cipherIn): end = len(cipherIn) ciphertext = cipherIn[start:end] if mode == self.ModeOfOperation["CFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(output) - 1 < i: plaintext[i] = 0 ^ ciphertext[i] elif len(ciphertext) - 1 < i: plaintext[i] = output[i] ^ 0 elif len(output) - 1 < i and len(ciphertext) < i: plaintext[i] = 0 ^ 0 else: plaintext[i] = output[i] ^ ciphertext[i] for k in range(end - start): chrOut.append(plaintext[k]) iput = ciphertext elif mode == self.ModeOfOperation["OFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(output) - 1 < i: plaintext[i] = 0 ^ ciphertext[i] elif len(ciphertext) - 1 < i: plaintext[i] = output[i] ^ 0 elif len(output) - 1 < i and len(ciphertext) < i: plaintext[i] = 0 ^ 0 else: plaintext[i] = output[i] ^ ciphertext[i] for k in range(end - start): chrOut.append(plaintext[k]) iput = output elif mode == self.ModeOfOperation["CBC"]: output = self.aes.decrypt(ciphertext, key, size) for i in range(16): if firstRound: plaintext[i] = IV[i] ^ output[i] else: plaintext[i] = iput[i] ^ output[i] firstRound = False if originalsize is not None and originalsize < end: for k in range(originalsize - start): chrOut.append(plaintext[k]) else: for k in range(end - start): chrOut.append(plaintext[k]) iput = ciphertext return chrOut def encryptData(key, data, mode=AESModeOfOperation.ModeOfOperation["CBC"]): """ Module function to encrypt the given data with the given key. @param key: key to be used for encryption @param data: data to be encrypted @param mode: mode of operations (0, 1 or 2) @return encrypted data prepended with the initialization vector """ if mode == AESModeOfOperation.ModeOfOperation["CBC"]: data = append_PKCS7_padding(data) keysize = len(key) assert keysize in AES.KeySize.values(), 'invalid key size: {}'.format(keysize) # Create a new iv using random data. iv = os.urandom(16) moo = AESModeOfOperation() (mode, length, ciph) = moo.encrypt(data, mode, key, keysize, iv) # With padding, the original length does not need to be known. # It's a bad idea to store the original message length prepend the iv. return iv + bytes(ciph) def decryptData(key, data, mode=AESModeOfOperation.ModeOfOperation["CBC"]): """ Module function to decrypt the given data with the given key. @param key: key to be used for decryption @param data: data to be decrypted with initialization vector prepended @param mode: mode of operations (0, 1 or 2) @return decrypted data """ keysize = len(key) assert keysize in AES.KeySize.values(), 'invalid key size: {}'.format(keysize) # iv is first 16 bytes. iv = data[:16] data = data[16:] moo = AESModeOfOperation() decr = moo.decrypt(data, None, mode, key, keysize, iv) if mode == AESModeOfOperation.ModeOfOperation["CBC"]: decr = strip_PKCS7_padding(decr) return decr class Test(object): def generateRandomKey(self, keysize): """ Generates a key from random data of length `keysize`. The returned key is a string of bytes. """ if keysize not in (16, 24, 32): raise ValueError('Invalid keysize, %s. Should be one of (16, 24, 32).' % keysize) return os.urandom(keysize) def testString(self, cleartext, keysize = 16, modeName = "CBC"): """ Test with random key, choice of mode. """ print('Random key test with Mode:', modeName) print('ClearText:', cleartext) key = self.generateRandomKey(keysize) print('Key:', bytes([x for x in key])) mode = AESModeOfOperation.ModeOfOperation[modeName] cipher = encryptData(key, cleartext, mode) print('Cipher:', bytes([x for x in cipher])) decr = decryptData(key, cipher, mode) print('Decrypted:', bytes(decr)) if __name__ == "__main__": moo = AESModeOfOperation() cleartext = "This is a test with several blocks ! Some utf-8 characters åäö and test continues" print('ClearText: %s\n' % cleartext) cleartext = bytes(cleartext, 'utf-8') cipherkey = [143, 194, 34, 208, 145, 203, 230, 143, 177, 246, 97, 206, 145, 92, 255, 84] iv = [103, 35, 148, 239, 76, 213, 47, 118, 255, 222, 123, 176, 106, 134, 98, 92] mode, orig_len, ciph = moo.encrypt(cleartext, moo.ModeOfOperation["CBC"], cipherkey, moo.aes.KeySize["SIZE_128"], iv) print('Encrypt result: mode = %s, length = %s (%s), encrypted = %s\n' % (mode, orig_len, len(cleartext), bytes(ciph))) decr = moo.decrypt(ciph, orig_len, mode, cipherkey, moo.aes.KeySize["SIZE_128"], iv) print('Decrypt result: %s\n' % bytes(decr)) Test().testString(cleartext, 16, "CBC")