def decrypt_ECB(key, text, strip_padding=True):
cipher = AES.AESCipher(key, AES.MODE_ECB)
decrypted = cipher.decrypt(text)
# Strip padding when decrypting whole messages.
# Don't do it if only decrypting a single block.
if strip_padding:
return unpad(decrypted)
else:
return decrypted
def decrypt_CBC(key, text):
block_size = 16
cipher_blocks = generate_blocks(text, block_size)
initialisation_vector = b'\x00' * block_size
cipher_blocks.insert(0, initialisation_vector)
text_blocks = []
for i in range(len(cipher_blocks) - 1):
decrypted = decrypt_ECB(key, cipher_blocks[i + 1], strip_padding=False)
text_blocks.append(fixed_xor(cipher_blocks[i], decrypted))
return unpad("".join(text_blocks))
