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AES_CBC.py
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AES_CBC.py
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import sys
import binascii
from math import floor
s_box = [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]
matrix = [2, 3, 1, 1,
1, 2, 3, 1,
1, 1, 2, 3,
3, 1, 1, 2]
inv_matrix = [14, 11, 13, 9,
9, 14, 11, 13,
13, 9, 14, 11,
11, 13, 9, 14]
rcon = ["01", "0", "0", "0", "02", "0", "0", "0",
"04", "0", "0", "0", "08", "0", "0", "0",
"10", "0", "0", "0", "20", "0", "0", "0",
"40", "0", "0", "0", "80", "0", "0", "0",
"1b", "0", "0", "0", "36", "0", "0", "0"]
def hexify(text):
list = []
text = binascii.hexlify(text)
for num in range(0, len(text), 2):
list.append(text[num:num+2])
return list
def zero(byte):
if len(byte) < 2:
return "0" + byte
return byte
def xor(message, key):
xored = []
for i in range(len(key)):
xored.append(zero(hex(int(message[i], 16) ^ int(key[i], 16))[2:]))
return xored
def padder(message):
global reps
if len(message) > 16:
if len(message) % 16 != 0:
message += "0" * (16 - (len(message) % 16))
reps = len(message) / 16
elif len(message) < 16:
message += "0" * (16 - len(message))
reps += 1
else:
reps = 1
return message
def bin_padding(binary):
binary = bin(binary)[2:]
return "0" * (8 - len(str(binary))) + binary
def key_check(key):
if len(key) < 16:
key += "0" * (16-len(key))
print key
elif len(key) > 16:
print "Error: Key bigger than 128 bits."
sys.exit(1)
def multiply(number, original, triply=0):
old_number = bin_padding(number)
number = bin(number<<1)[2:]
if len(number) > 8:
number = number[len(number)-8:]
if old_number[0] == "1":
number = int(number, 2) ^ int(bin(int("1B", 16)), 2)
else:
number = int(number, 2)
if triply == 1:
number ^= int(original, 2)
return number
def hex2ascii(hex):
ascii = []
for num in range(0, len(hex), 2):
ascii.append(hex[num:num+2])
return ascii
def SubBytes(message):
subbed = []
map(lambda char : subbed.append(hex(s_box[int(zero(char)[0], 16) * 16 + int(char[-1], 16)])[2:]), message)
return subbed
def ShiftRows(message):
shifted = []
map(lambda char : shifted.append(zero(char)), message)
for i in range(1, 4):
for k in range(i):
for j in range(0, 3):
shifted[i], shifted[i+12-j*4] = shifted[i+12-j*4], shifted[i]
return shifted
def MixColumns(message):
mixed = []
for k in range(4):
for i in range(4):
cell = 0
for j in range(4):
current = int(bin(int(message[j+4*k], 16)), 2)
old = bin_padding(current)
if matrix[j+i*4] == 2:
current = multiply(current, old)
elif matrix[j+i*4] == 3:
current = multiply(current, old, 1)
cell = int(bin(cell), 2) ^ current
mixed.append(zero(hex(cell)[2:]))
return mixed
def KeySchedule(key, t):
segment, newkey = [], []
for i in range(12, 16):
segment.append(key[i])
for i in range(3, 0, -1):
segment[0], segment[i] = segment[i], segment[0]
segment = SubBytes(segment)
i = 0
while len(newkey) < 4:
newkey.append(hex(int(key[i], 16) ^ int(segment[i], 16) ^ int(rcon[4*t+i], 16))[2:])
i += 1
for i in range(12):
newkey.append(hex(int(key[i+4], 16) ^ int(newkey[i], 16))[2:])
return newkey
def invSubBytes(ciphertext):
unsubbed = []
for char in ciphertext:
char = "0x" + char
unsubbed.append("%X" % (floor(s_box.index(int(char, 16)) / 16)) + "%X" % (s_box.index(int(char, 16)) % 16))
return unsubbed
def invShiftRows(ciphertext):
unshifted = []
map(lambda char : unshifted.append(zero(char)), ciphertext)
for i in range(1, 4):
for k in range(i):
for j in range(3, 0, -1):
unshifted[i+12], unshifted[i+12-j*4] = unshifted[i+12-j*4], unshifted[i+12]
return unshifted
def invMixColumns(ciphertext):
unmixed = []
for k in range(4):
for l in range(4):
cell = 0
for j in range(0, 4):
current = int(bin(int(ciphertext[j+4*k], 16)), 2)
old = bin_padding(current)
if inv_matrix[j+l*4] == 9:
for i in range(2):
current = multiply(current, old)
current = multiply(current, old, 1)
elif inv_matrix[j+l*4] == 11:
current = multiply(current, old)
for i in range(2):
current = multiply(current, old, 1)
elif inv_matrix[j+l*4] == 13:
current = multiply(current, old, 1)
current = multiply(current, old)
current = multiply(current, old, 1)
elif inv_matrix[j+l*4] == 14:
for i in range(2):
current = multiply(current, old, 1)
current = multiply(current, old)
cell = int(bin(cell), 2) ^ current
unmixed.append(zero(hex(cell)[2:]))
return unmixed
def encrypt(message, key, iv):
original = key
final = ""
for rep in range(1, reps+1):
if rep == 1:
xored = xor(message[((rep-1)*16):(16*rep)], iv)
else:
xored = xor(message[((rep-1)*16):(16*rep)], cipher)
xored = xor(xored, original)
for j in range(1, 10):
keyx = original
for round in range(j):
keyx = KeySchedule(keyx, round)
subbed = SubBytes(xored)
shifted = ShiftRows(subbed)
mixed = MixColumns(shifted)
xored = xor(mixed, keyx)
subbed = SubBytes(xored)
shifted = ShiftRows(subbed)
key = KeySchedule(keyx, 9)
cipher = xor(shifted, key)
final += "".join(cipher)
return final
def decrypt(ciphertext, originalkey, iv):
message = ""
lastkey = originalkey
for i in range(10):
lastkey = KeySchedule(lastkey, i)
for rep in range(1, reps+1):
cipher = ciphertext[((rep-1)*16):(16*rep)]
xored = xor(cipher, lastkey)
unshifted = invShiftRows(xored)
unsubbed = invSubBytes(unshifted)
for round in range(9, 0, -1):
key = originalkey
for kround in range(round):
key = KeySchedule(key, kround)
xored = xor(unsubbed, key)
unmixed = invMixColumns(xored)
unshifted = invShiftRows(unmixed)
unsubbed = invSubBytes(unshifted)
xored = xor(unsubbed, originalkey)
if rep == 1:
xored = xor(xored, iv)
else:
xored = xor(xored, ciphertext[((rep-2)*16):(16*(rep-1))])
message += "".join(xored)
return binascii.unhexlify(message)
if __name__ == "__main__":
import pyperclip
mode = "encrypt"
reps = 0
iv = hexify("12345")
for i in range(16 - len(iv)):
iv.append("0")
key = hexify("now we try a key")
message = padder(hexify("This is just a test for my AES implementation."))
if mode == "encrypt" or mode[0] == "e":
result = encrypt(message, key, iv).upper()
elif mode == "decrypt" or mode[0] == "d":
result = decrypt(padder(hex2ascii("F9D4661071CA7B51A1C10360AD7BF5195FC505FD4A4B3DD6FAAA649EAF78430822FECF1FF1DEA3D63CCF3E423F805C94".upper())), key, iv)
print result
pyperclip.copy(result)