#!/usr/bin/python2.5
import sys, hashlib, string, getpass
from copy import copy
# The actual Rijndael specification includes variable block size, but
# AES uses a fixed block size of 16 bytes (128 bits)
# Additionally, AES allows for a variable key size, though this implementation
# of AES uses only 256-bit cipher keys (AES-256)
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
]
sboxInv = [
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
]
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
]
# returns a copy of the word shifted n bytes (chars)
# positive values for n shift bytes left, negative values shift right
def rotate(word, n):
return word[n:]+word[0:n]
# iterate over each "virtual" row in the state table and shift the bytes
# to the LEFT by the appropriate offset
def shiftRows(state):
for i in range(4):
state[i*4:i*4+4] = rotate(state[i*4:i*4+4],i)
# iterate over each "virtual" row in the state table and shift the bytes
# to the RIGHT by the appropriate offset
def shiftRowsInv(state):
for i in range(4):
state[i*4:i*4+4] = rotate(state[i*4:i*4+4],-i)
# takes 4-byte word and iteration number
def keyScheduleCore(word, i):
# rotate word 1 byte to the left
word = rotate(word, 1)
newWord = []
# apply sbox substitution on all bytes of word
for byte in word:
newWord.append(sbox[byte])
# XOR the output of the rcon[i] transformation with the first part of the word
newWord[0] = newWord[0]^rcon[i]
return newWord
# expand 256 bit cipher key into 240 byte key from which
# each round key is derived
def expandKey(cipherKey):
cipherKeySize = len(cipherKey)
assert cipherKeySize == 32
# container for expanded key
expandedKey = []
currentSize = 0
rconIter = 1
# temporary list to store 4 bytes at a time
t = [0,0,0,0]
# copy the first 32 bytes of the cipher key to the expanded key
for i in range(cipherKeySize):
expandedKey.append(cipherKey[i])
currentSize += cipherKeySize
# generate the remaining bytes until we get a total key size
# of 240 bytes
while currentSize < 240:
# assign previous 4 bytes to the temporary storage t
for i in range(4):
t[i] = expandedKey[(currentSize - 4) + i]
# every 32 bytes apply the core schedule to t
if currentSize % cipherKeySize == 0:
t = keyScheduleCore(t, rconIter)
rconIter += 1
# since we're using a 256-bit key -> add an extra sbox transform
if currentSize % cipherKeySize == 16:
for i in range(4):
t[i] = sbox[t[i]]
# XOR t with the 4-byte block [16,24,32] bytes before the end of the
# current expanded key. These 4 bytes become the next bytes in the
# expanded key
for i in range(4):
expandedKey.append(((expandedKey[currentSize - cipherKeySize]) ^ (t[i])))
currentSize += 1
return expandedKey
# do sbox transform on each of the values in the state table
def subBytes(state):
for i in range(len(state)):
#print "state[i]:", state[i]
#print "sbox[state[i]]:", sbox[state[i]]
state[i] = sbox[state[i]]
# inverse sbox transform on each byte in state table
def subBytesInv(state):
for i in range(len(state)):
state[i] = sboxInv[state[i]]
# XOR each byte of the roundKey with the state table
def addRoundKey(state, roundKey):
for i in range(len(state)):
#print i
#print "old state value:", state[i]
#print "new state value:", state[i] ^ roundKey[i]
state[i] = state[i] ^ roundKey[i]
# Galois Multiplication
def galoisMult(a, b):
p = 0
hiBitSet = 0
for i in range(8):
if b & 1 == 1:
p ^= a
hiBitSet = a & 0x80
a <<= 1
if hiBitSet == 0x80:
a ^= 0x1b
b >>= 1
return p % 256
# mixColumn takes a column and does stuff
def mixColumn(column):
temp = copy(column)
column[0] = galoisMult(temp[0],2) ^ galoisMult(temp[3],1) ^ \
galoisMult(temp[2],1) ^ galoisMult(temp[1],3)
column[1] = galoisMult(temp[1],2) ^ galoisMult(temp[0],1) ^ \
galoisMult(temp[3],1) ^ galoisMult(temp[2],3)
column[2] = galoisMult(temp[2],2) ^ galoisMult(temp[1],1) ^ \
galoisMult(temp[0],1) ^ galoisMult(temp[3],3)
column[3] = galoisMult(temp[3],2) ^ galoisMult(temp[2],1) ^ \
galoisMult(temp[1],1) ^ galoisMult(temp[0],3)
# mixColumnInv does stuff too
def mixColumnInv(column):
temp = copy(column)
column[0] = galoisMult(temp[0],14) ^ galoisMult(temp[3],9) ^ \
galoisMult(temp[2],13) ^ galoisMult(temp[1],11)
column[1] = galoisMult(temp[1],14) ^ galoisMult(temp[0],9) ^ \
galoisMult(temp[3],13) ^ galoisMult(temp[2],11)
column[2] = galoisMult(temp[2],14) ^ galoisMult(temp[1],9) ^ \
galoisMult(temp[0],13) ^ galoisMult(temp[3],11)
column[3] = galoisMult(temp[3],14) ^ galoisMult(temp[2],9) ^ \
galoisMult(temp[1],13) ^ galoisMult(temp[0],11)
# mixColumns is a wrapper for mixColumn - generates a "virtual" column from
# the state table and applies the weird galois math
def mixColumns(state):
for i in range(4):
column = []
# create the column by taking the same item out of each "virtual" row
for j in range(4):
column.append(state[j*4+i])
# apply mixColumn on our virtual column
mixColumn(column)
# transfer the new values back into the state table
for j in range(4):
state[j*4+i] = column[j]
# mixColumnsInv is a wrapper for mixColumnInv - generates a "virtual" column from
# the state table and applies the weird galois math
def mixColumnsInv(state):
for i in range(4):
column = []
# create the column by taking the same item out of each "virtual" row
for j in range(4):
column.append(state[j*4+i])
# apply mixColumn on our virtual column
mixColumnInv(column)
# transfer the new values back into the state table
for j in range(4):
state[j*4+i] = column[j]
# aesRound applies each of the four transformations in order
def aesRound(state, roundKey):
#print "aesRound - before subBytes:", state
subBytes(state)
#print "aesRound - before shiftRows:", state
shiftRows(state)
#print "aesRound - before mixColumns:", state
mixColumns(state)
#print "aesRound - before addRoundKey:", state
addRoundKey(state, roundKey)
#print "aesRound - after addRoundKey:", state
# aesRoundInv applies each of the four inverse transformations
def aesRoundInv(state, roundKey):
#print "aesRoundInv - before addRoundKey:", state
addRoundKey(state, roundKey)
#print "aesRoundInv - before mixColumnsInv:", state
mixColumnsInv(state)
#print "aesRoundInv - before shiftRowsInv:", state
shiftRowsInv(state)
#print "aesRoundInv - before subBytesInv:", state
subBytesInv(state)
#print "aesRoundInv - after subBytesInv:", state
# returns a 16-byte round key based on an expanded key and round number
def createRoundKey(expandedKey, n):
return expandedKey[(n*16):(n*16+16)]
# create a key from a user-supplied password using SHA-256
def passwordToKey(password):
sha256 = hashlib.sha256()
sha256.update(password)
key = []
for c in list(sha256.digest()):
key.append(ord(c))
return key
# wrapper function for 14 rounds of AES since we're using a 256-bit key
def aesMain(state, expandedKey, numRounds=14):
roundKey = createRoundKey(expandedKey, 0)
addRoundKey(state, roundKey)
for i in range(1, numRounds):
roundKey = createRoundKey(expandedKey, i)
aesRound(state, roundKey)
# final round - leave out the mixColumns transformation
roundKey = createRoundKey(expandedKey, numRounds)
subBytes(state)
shiftRows(state)
addRoundKey(state, roundKey)
# 14 rounds of AES inverse since we're using a 256-bit key
def aesMainInv(state, expandedKey, numRounds=14):
# create roundKey for "last" round since we're going in reverse
roundKey = createRoundKey(expandedKey, numRounds)
# addRoundKey is the same funtion for inverse since it uses XOR
addRoundKey(state, roundKey)
shiftRowsInv(state)
subBytesInv(state)
for i in range(numRounds-1,0,-1):
roundKey = createRoundKey(expandedKey, i)
aesRoundInv(state, roundKey)
# last round - leave out the mixColumns transformation
roundKey = createRoundKey(expandedKey, 0)
addRoundKey(state, roundKey)
# aesEncrypt - encrypt a single block of plaintext
def aesEncrypt(plaintext, key):
block = copy(plaintext)
expandedKey = expandKey(key)
aesMain(block, expandedKey)
return block
# aesDecrypt - decrypte a single block of ciphertext
def aesDecrypt(ciphertext, key):
block = copy(ciphertext)
expandedKey = expandKey(key)
aesMainInv(block, expandedKey)
return block
# return 16-byte block from an open file
# pad to 16 bytes with null chars if needed
def getBlock(fp):
raw = fp.read(16)
# reached end of file
if len(raw) == 0:
return ""
# container for list of bytes
block = []
for c in list(raw):
block.append(ord(c))
# if the block is less than 16 bytes, pad the block
# with the string representing the number of missing bytes
if len(block) < 16:
padChar = 16-len(block)
while len(block) < 16:
block.append(padChar)
return block
# encrypt - wrapper function to allow encryption of arbitray length
# plaintext using Output Feedback (OFB) mode
def encrypt(myInput, password, outputfile=None):
block = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # plaintext
ciphertext = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # ciphertext
# Initialization Vector
IV = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
# convert password to AES 256-bit key
aesKey = passwordToKey(password)
# create handle for file to be encrypted
try:
fp = open(myInput, "rb")
except:
print "pyAES: unable to open input file -", myInput
sys.exit()
# create handle for encrypted output file
if outputfile is not None:
try:
outfile = open(outputfile,"w")
except:
print "pyAES: unable to open output file -", filename
sys.exit()
else:
filename = myInput+".aes"
try:
outfile = open(filename,"w")
except:
print "pyAES: unable to open output file -", filename
sys.exit()
# begin reading in blocks of input to encrypt
firstRound = True
block = getBlock(fp)
while block != "":
if firstRound:
blockKey = aesEncrypt(IV, aesKey)
firstRound = False
else:
blockKey = aesEncrypt(blockKey, aesKey)
for i in range(16):
ciphertext[i] = block[i] ^ blockKey[i]
# write ciphertext to outfile
for c in ciphertext:
outfile.write(chr(c))
# grab next block from input file
block = getBlock(fp)
# close file pointers
fp.close()
outfile.close()
# decrypt - wrapper function to allow decryption of arbitray length
# ciphertext using Output Feedback (OFB) mode
def decrypt(myInput, password, outputfile=None):
block = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # ciphertext
plaintext = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # plaintext container
# Initialization Vector
IV = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
# convert password to AES 256-bit key
aesKey = passwordToKey(password)
# create handle for file to be encrypted
try:
fp = open(myInput, "rb")
except:
print "pyAES: unable to open input file -", myInput
sys.exit()
# get the file size (bytes) in order to handle the
# padding at the end of the file
fp.seek(0,2)
filesize = fp.tell()
# put the file pointer back at the beginning of the file
fp.seek(0)
# create handle for file to be decrypted
try:
fp = open(myInput, "rb")
except:
print "pyAES: unable to open input file -", myInput
sys.exit()
# create handle for decrypted output file
if outputfile is not None:
try:
outfile = open(outputfile,"w")
except:
print "pyAES: unable to open output file -", filename
sys.exit()
else:
if myInput[-4:] == ".aes":
filename = myInput[:-4]
print "Using", filename, "for output file name."
else:
filename = raw_input("output file name: ")
try:
outfile = open(filename,"w")
except:
print "pyAES: unable to open output file -", filename
sys.exit()
# begin reading in blocks of input to decrypt
firstRound = True
block = getBlock(fp)
while block != "":
if firstRound:
blockKey = aesEncrypt(IV, aesKey)
firstRound = False
else:
blockKey = aesEncrypt(blockKey, aesKey)
for i in range(16):
plaintext[i] = block[i] ^ blockKey[i]
# if we're in the last block of text -> throw out the
# number of bytes represented by the last byte in the block
if fp.tell() == filesize:
plaintext = plaintext[0:-(plaintext[-1])]
# write ciphertext to outfile
for c in plaintext:
outfile.write(chr(c))
# grab next block from input file
block = getBlock(fp)
# close file pointers
fp.close()
outfile.close()
def printUsage():
print "./pyAES.py [-e | -d ] [(optional) -o