--aes.py--

Admin Posts : 22 Join date : 2011-09-21

-C-h-a-n-g-e-s--------------------
--(Code writer in source) Pulled source from http://trac.poke-lab.com/browser
-------------------------------------
-S-o-u-r-c-e-----------------------

Code:: #!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# AES - Advanced Encryption Standard
#
# Copyright (c) 2007 Josh Davis ( http://www.josh-davis.org ),
# Laurent Haan ( http://www.progressive-coding.com )
#
# Licensed under the MIT License ( http://www.opensource.org/licenses/mit-license.php ):
#
import math

class AES:
#
# START AES SECTION
#

#structure of 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 ]
# retrieves a given S-Box Value
def getSBoxValue(self,num): return self.sbox[num]
# retrieves a given Inverted S-Box Value
def getSBoxInvert(self,num): return self.rsbox[num]
#
# Rijndael's key schedule rotate operation
# rotate the word eight bits to the left
#
# rotate(1d2c3a4f) = 2c3a4f1d
#
# word is an char array of size 4 (32 bit)
#
def rotate(self,word):
c = word[0]
for i in range(3): word[i] = word[i+1]
word[3] = c

return word
# 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 ]
# gets a given Rcon value
def getRconValue(self,num): return self.Rcon[num]
# Key Schedule Core
def core(self,word, iteration):
# 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
#
# Rijndael's key expansion
# expands an 128,192,256 key into an 176,208,240 bytes key
#
# expandedKey is a pointer to an char array of large enough size
# key is a pointer to a non-expanded key
#
def expandKey(self,key, size, expandedKeySize):
# current expanded keySize, in bytes
currentSize = 0
rconIteration = 1
# temporary 4-byte variable
t = [0,0,0,0]

expandedKey = []
while len(expandedKey) < expandedKeySize:
expandedKey.append(0)

# 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
for k in range(4): t[k] = expandedKey[(currentSize - 4) + k]
#
# 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
# Adds (XORs) the round key to the state
def addRoundKey(self,state, roundKey):
for i in range(16):
state[i] ^= roundKey[i]
return state
# Creates a round key from the given expanded key and the
# position within the expanded key.
def createRoundKey(self,expandedKey,roundKeyPointer):
roundKey = [];
while len(roundKey) < 16:
roundKey.append(0)
for i in range(4):
for j in range(4):
roundKey[j*4+i] = expandedKey[roundKeyPointer + i*4 + j]
return roundKey
# galois multiplication of 8 bit characters a and b
def galois_multiplication(self,a, b):
p = 0
for counter in range(8):
if (b & 1) == 1: p ^= a
if p > 0x100: p ^= 0x100
# keep p 8 bit
hi_bit_set = (a & 0x80)
a <<= 1
if a > 0x100:
# keep a 8 bit
a ^= 0x100
if hi_bit_set == 0x80:
a ^= 0x1b
if a > 0x100:
# keep a 8 bit
a ^= 0x100
b >>= 1
if b > 0x100:
# keep b 8 bit
b ^= 0x100

return p
#
# substitute all the values from the state with the value in the SBox
# using the state value as index for the SBox
#
def subBytes(self,state,isInv):
for i in range(16):
if isInv: state[i] = self.getSBoxInvert(state[i])
else: state[i] = self.getSBoxValue(state[i])
return state
# iterate over the 4 rows and call shiftRow() with that row
def shiftRows(self,state,isInv):
for i in range(4):
state = self.shiftRow(state,i*4, i,isInv)
return state
# each iteration shifts the row to the left by 1
def shiftRow(self,state,statePointer,nbr,isInv):
for i in range(nbr):
if isInv:
tmp = state[statePointer + 3]
j = 3
while j > 0:
state[statePointer + j] = state[statePointer + j-1]
j -= 1;
state[statePointer] = tmp
else:
tmp = state[statePointer]
for j in range(3):
state[statePointer + j] = state[statePointer + j+1]
state[statePointer + 3] = tmp
return state
# galois multipication of the 4x4 matrix
def mixColumns(self,state,isInv):
column = [0,0,0,0]
# iterate over the 4 columns
for i in range(4):
# construct one column by iterating over the 4 rows
for j in range(4): column[j] = state[(j*4)+i]
# apply the mixColumn on one column
column = self.mixColumn(column,isInv)
# put the values back into the state
for k in range(4): state[(k*4)+i] = column[k]

return state;
# galois multipication of 1 column of the 4x4 matrix
def mixColumn(self,column,isInv):
mult = []
if isInv: mult = [14,9,13,11]
else: mult = [2,1,1,3]
cpy = [0,0,0,0]
for i in range(4): cpy[i] = column[i]

column[0] = self.galois_multiplication(cpy[0],mult[0]) ^ self.galois_multiplication(cpy[3],mult[1]) ^ self.galois_multiplication(cpy[2],mult[2]) ^ self.galois_multiplication(cpy[1],mult[3])
column[1] = self.galois_multiplication(cpy[1],mult[0]) ^ self.galois_multiplication(cpy[0],mult[1]) ^ self.galois_multiplication(cpy[3],mult[2]) ^ self.galois_multiplication(cpy[2],mult[3])
column[2] = self.galois_multiplication(cpy[2],mult[0]) ^ self.galois_multiplication(cpy[1],mult[1]) ^ self.galois_multiplication(cpy[0],mult[2]) ^ self.galois_multiplication(cpy[3],mult[3])
column[3] = self.galois_multiplication(cpy[3],mult[0]) ^ self.galois_multiplication(cpy[2],mult[1]) ^ self.galois_multiplication(cpy[1],mult[2]) ^ self.galois_multiplication(cpy[0],mult[3])
return column

# applies the 4 operations of the forward round in sequence
def aes_round(self,state, roundKey):
state = self.subBytes(state,False)
state = self.shiftRows(state,False)
state = self.mixColumns(state,False)
state = self.addRoundKey(state, roundKey)
return state

# applies the 4 operations of the inverse round in sequence
def aes_invRound(self,state, roundKey):
state = self.shiftRows(state,True)
state = self.subBytes(state,True)
state = self.addRoundKey(state, roundKey)
state = self.mixColumns(state,True)
return state

#
# Perform the initial operations, the standard round, and the final operations
# of the forward aes, creating a round key for each round
#
def aes_main(self,state, expandedKey, nbrRounds):
state = self.addRoundKey(state, self.createRoundKey(expandedKey,0))
i = 1
while i < nbrRounds:
state = self.aes_round(state, self.createRoundKey(expandedKey,16*i))
i += 1
state = self.subBytes(state,False)
state = self.shiftRows(state,False)
state = self.addRoundKey(state, self.createRoundKey(expandedKey,16*nbrRounds))
return state

#
# Perform the initial operations, the standard round, and the final operations
# of the inverse aes, creating a round key for each round
#
def aes_invMain(self,state, expandedKey, nbrRounds):
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 -= 1
state = self.shiftRows(state,True)
state = self.subBytes(state,True)
state = self.addRoundKey(state, self.createRoundKey(expandedKey,0))
return state

# encrypts a 128 bit input block against the given key of size specified
def encrypt(self,iput, key, size):
output = []
while len(output) < 16:
output.append(0)
# the number of rounds
nbrRounds = 0
# the 128 bit block to encode
block = []
# 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
else: return None

# the expanded keySize
expandedKeySize = (16*(nbrRounds+1))
#
# Set the block values, for the block:
# a0,0 a0,1 a0,2 a0,3
# a1,0 a1,1 a1,2 a1,3
# a2,0 a2,1 a2,2 a2,3
# a3,0 a3,1 a3,2 a3,3
# the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
#
while len(block) < 16:
block.append(0)
# iterate over the columns
for i in range(4):
# iterate over the rows
for j in range(4):
block[(i+(j*4))] = iput[(i*4)+j]

# expand the key into an 176, 208, 240 bytes key
# the expanded 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):
# iterate over the rows
for l in range(4):
output[(k*4)+l] = block[(k+(l*4))]
return output

# decrypts a 128 bit input block against the given key of size specified
def decrypt(self,iput, key, size):
output = []
while len(output) < 16:
output.append(0)
# the number of rounds
nbrRounds = 0
# the 128 bit block to decode
block = []
while len(block) < 16:
block.append(0)
# 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
else: return None

# the expanded keySize
expandedKeySize = (16*(nbrRounds+1))
#
# Set the block values, for the block:
# a0,0 a0,1 a0,2 a0,3
# a1,0 a1,1 a1,2 a1,3
# a2,0 a2,1 a2,2 a2,3
# a3,0 a3,1 a3,2 a3,3
# the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
#

# iterate over the columns
for i in range(4):
# iterate over the rows
for j in range(4):
block[(i+(j*4))] = iput[(i*4)+j]
# expand the key into an 176, 208, 240 bytes 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):
# iterate over the rows
for l in range(4):
output[(k*4)+l] = block[(k+(l*4))]
return output

#
# END AES SECTION
#

class AESModeOfOperation:
#
# START MODE OF OPERATION SECTION
#
aes = AES()

# structure of supported modes of operation
modeOfOperation = {
"OFB":0,
"CFB":1,
"CBC":2}
# converts a 16 character string into a number array
def convertString(self,string,start,end,mode):
if end - start > 16: end = start + 16
if mode == self.modeOfOperation["CBC"]: ar = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
else: ar = []

i = start
j = 0
while len(ar) < end - start:
ar.append(0)
while i < end:
ar[j] = ord(string[i])
j += 1
i += 1
return ar

#
# Mode of Operation Encryption
# stringIn - Input String
# mode - mode of type modeOfOperation
# hexKey - a hex key of the bit length size
# size - the bit length of the key
# hexIV - the 128 bit hex Initilization Vector
#
def encrypt(self,stringIn,mode,key,size,IV):
if len(key)%size:
return None
if len(IV)%16:
return None
# the AES input/output
plaintext = []
iput = []
output = []
ciphertext = []
while len(ciphertext) < 16:
ciphertext.append(0)
# the output cipher string
cipherOut = []
# char firstRound
firstRound = True
if stringIn != None:
for j in range(int(math.ceil(float(len(stringIn))/16))):
start = j*16
end = j*16+16
if j*16+16 > 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] ^ ciphertext[i]
else:
iput[i] = plaintext[i] ^ IV[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

#
# Mode of Operation Decryption
# cipherIn - Encrypted String
# originalsize - The unencrypted string length - required for CBC
# mode - mode of type modeOfOperation
# key - a number array of the bit length size
# size - the bit length of the key
# IV - the 128 bit number array Initilization Vector
#
def decrypt(self,cipherIn,originalsize,mode,key,size,IV):
# cipherIn = unescCtrlChars(cipherIn)
if len(key)%size:
return None
if len(IV)%16:
return None
# the AES input/output
ciphertext = []
iput = []
output = []
plaintext = []
while len(plaintext) < 16:
plaintext.append(0)
# the output plain text string
stringOut = ''
# char firstRound
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]
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):
stringOut += chr(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):
stringOut += chr(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 < end:
for k in range(originalsize-start):
stringOut += chr(plaintext[k])
else:
for k in range(end-start):
stringOut += chr(plaintext[k])
iput = ciphertext;
return stringOut;

#
# END MODE OF OPERATION SECTION
#

if __name__ == "__main__":
moo = AESModeOfOperation()
mode,orig_len,ciph = moo.encrypt("This is a test!",moo.modeOfOperation["OFB"],[143,194,34,208,145,203,230,143,177,246,97,206,145,92,255,84],moo.aes.keySize["SIZE_128"],[103,35,148,239,76,213,47,118,255,222,123,176,106,134,98,92])
print ciph
decr = moo.decrypt(ciph,orig_len,mode,[143,194,34,208,145,203,230,143,177,246,97,206,145,92,255,84],moo.aes.keySize["SIZE_128"],[103,35,148,239,76,213,47,118,255,222,123,176,106,134,98,92])
print decr

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