def encryption_oracle(msg: bytes,
a: int = 5,
b: int = 10,
keysize: int = 16) -> tuple:
pre = Random.get_random_bytes(random.randint(a, b))
post = Random.get_random_bytes(random.randint(a, b))
key = block.gen_random_aes_key()
iv = Random.get_random_bytes(keysize)
msg = pre + msg + post
if random.randint(0, 1) > 0:
return block.aes_ecb_encrypt(msg, key), 'ECB'
else:
return block.aes_cbc_encrypt(msg, key, iv), 'CBC'
from cryptopals import block
from cryptopals import basic
from Crypto import Random
import base64
def bitflipping_oracle_encrypt(plaintext, aes_key, iv: bytes) -> bytes:
prepend = b'comment1=cooking%20MCs;userdata='
append = b';comment2=%20like%20a%20pound%20of%20bacon'
plaintext = plaintext.replace(b'=',b'"="')
plaintext = plaintext.replace(b';',b'";"')
return block.aes_cbc_encrypt(prepend + plaintext + append, key, iv)
# This just returns True or False to see if the data is an admin.
def bitflipping_oracle_decrypt(ciphertext, aes_key, iv: bytes) -> bool:
plaintext = block.aes_cbc_decrypt(ciphertext, aes_key, iv)
print(plaintext)
return b';admin=true;' in plaintext
if __name__ == '__main__':
key = block.gen_random_aes_key()
iv = Random.get_random_bytes(16)
ciphertext = bitflipping_oracle_encrypt(b'YELLOW SUBMARINE',key,iv)
differing_bits = basic.fixed_xor(b'YELLOW SUBMARINE', b';admin=true;4444') # pad so it's the same length.
new_block = basic.fixed_xor(differing_bits, ciphertext[16:32])
ciphertext = ciphertext[0:16] + new_block + ciphertext[32:]
bitflipping_oracle_decrypt(ciphertext, key, iv)
base64.b64decode('MDAwMDAyUXVpY2sgdG8gdGhlIHBvaW50LCB0byB0aGUgcG9pbnQsIG5vIGZha2luZw==')
def __init__(self, stringfile: str):
self.key = block.gen_random_aes_key()
with open(stringfile) as f:
self.choices = [base64.b64decode(s) for s in f]