def get_replacement_byte(orig, new):
h1 = str(binascii.hexlify(my_encode(orig)))[2:-1]
h2 = str(binascii.hexlify(my_encode("x")))[2:-1]
h3 = str(binascii.hexlify(my_encode(new)))[2:-1]
temp = binary_xor(h1, h2)
r_byte = binary_xor(bin2hex(temp), h3)
return r_byte
def decrypt_cbc(c, k, iv, padding):
# make list of blocks
blocks = []
for i in range(0, int(len(c)/16)):
b = c[i * 16:i * 16 + 16]
blocks.append(b)
# decrypt and xor to get plaintext
h1 = binascii.hexlify(iv)
plain_blocks = []
for b in blocks:
undo_aes = my_encode(decrypt_ecb(b, k))
h2 = binascii.hexlify(undo_aes)
x = binary_xor(h1.decode('latin1'), h2.decode('latin1'))
h1 = binascii.hexlify(b) # update h1 for next iteration
x = hex(int(x, 2))[2:].zfill(32)
plain_block = str(binascii.unhexlify(x), 'latin1')
plain_blocks.append(plain_block)
plaintext = ''.join(plain_blocks)
if padding:
return chop(plaintext)
else:
return plaintext
def encrypt_cbc(p, k, iv):
p = pkcs7_pad(p.decode('latin1'), 128)
# make list of blocks
blocks = []
for i in range(0, int(len(p) / 16)):
b = p[i * 16:i * 16 + 16]
blocks.append(b)
# xor and encrypt to get ciphertext
h1 = binascii.hexlify(iv)
c_text = []
for b in blocks:
h2 = binascii.hexlify(b)
x = binary_xor(h1.decode('latin1'), h2.decode('latin1'))
x = hex(int(x, 2))[2:].zfill(32)
do_aes = encrypt_ecb(binascii.unhexlify(x), k, False)
h1 = binascii.hexlify(do_aes) # update h1 for next iteration
c_text.append(str(do_aes, 'latin1'))
return ''.join(c_text)
def decrypt_cbc(c, k, iv):
# make list of blocks
blocks = []
for i in range(0, int(len(c) / 16)):
b = c[i * 16:i * 16 + 16]
blocks.append(b)
# decrypt and xor to get plaintext
h1 = binascii.hexlify(iv)
plain_blocks = []
for b in blocks:
undo_aes = my_encode(decrypt_ecb(b, k))
h2 = binascii.hexlify(undo_aes)
x = binary_xor(h1.decode('latin1'), h2.decode('latin1'))
h1 = binascii.hexlify(b) # update h1 for next iteration
x = hex(int(x, 2))[2:].zfill(32)
plain_block = str(binascii.unhexlify(x), 'latin1')
plain_blocks.append(plain_block)
plaintext = ''.join(plain_blocks)
# chop off any pkcs7 padding
b_array = bytearray(str.encode(plaintext))
last_byte = b_array[-1]
if last_byte <= 16:
padding_found = True
for i in range(1, last_byte + 1):
if b_array[0 - i] != i:
padding_found = False
break
if padding_found:
for i in range(0, last_byte):
b_array.pop()
return bytes(b_array).decode('ascii')
def three_xor(a1, a2, a3):
temp = binary_xor(a1, a2)
return binary_xor(bin2hex(temp), a3)