def main():
if len(sys.argv) < 3:
key = SAMPLE_KEY
filename = SAMPLE_FILENAME
else:
key = sys.argv[1]
filename = sys.argv[2]
f = open(filename, "r")
ciphertext = ""
for line in f:
ciphertext += common.b64decode(line.rstrip())
print common.aes_cbc_decrypt(ciphertext, key, "\x00" * 16)
if False:
for _ in range(1000):
key = common.randbytes(16)
pt = common.randbytes(random.randint(1, 64))
iv = common.randbytes(16)
AFTER = binascii.hexlify(common.aes_cbc_decrypt(common.aes_cbc_encrypt(pt, key, iv), key, iv))
PT = binascii.hexlify(common.pkcs7_pad(pt, len(pt) + (16 - (len(pt) % 16))))
print PT == AFTER
def aes_128_cbc_encrypt(data: bytes, key: bytes) -> bytes:
"""Encrypt a stream of bytes with the key using block chaining."""
# Make sure the data and key are the correct lengths
assert len(key) == 16
data = pkcs7_pad(data)
# Create an output buffer for blocks and add to it one at a time
# The buffer is initialized with the IV.
buf = [b'\0' * 16]
for block in [data[i:i + 16] for i in range(0, len(data), 16)]:
buf.append(aes_128_ecb_encrypt(xor_bytes(block, buf[-1]), key))
# Combine encrypted block back together, ignoring the IV
return b''.join(buf[1:])
def main():
# ECB round trip
plaintext = b"""Now is the time for all good men to come to the aid of their
country. Lorem ipsum dolor sit amet."""
plaintext = pkcs7_pad(plaintext)
key = b'cryptozoologists'
ciphertext = aes_128_ecb_encrypt(plaintext, key)
new_plaintext = aes_128_ecb_decrypt(ciphertext, key)
assert plaintext == new_plaintext
# CBC decryption of provided text
with open('10.txt') as file10:
ciphertext = base64_to_bytes(file10.read())
key = b'YELLOW SUBMARINE'
decipheredtext = aes_128_cbc_decrypt(ciphertext, key)
assert (decipheredtext.startswith(b"I'm back and I'm ringin' the bell"))
# CBC round trip
key = b'cryptozoologists'
ciphertext = aes_128_cbc_encrypt(plaintext, key)
new_plaintext = aes_128_cbc_decrypt(ciphertext, key)
assert plaintext == new_plaintext
print('Challenge 10 completed successfully.')
def main():
if len(sys.argv) != 3:
usage()
print common.pkcs7_pad(sys.argv[1], int(sys.argv[2]))