def oracle(ptext):
key, ecb_mode = make_aes_key(), random.getrandbits(1)
pre = bytes(random.getrandbits(8) for _ in range(random.randint(5, 10)))
post = bytes(random.getrandbits(8) for _ in range(random.randint(5, 10)))
ptext = pre + ptext + post
if ecb_mode:
ctext = aes_ecb_encrypt(ptext, key)
else:
iv = make_aes_key()
ctext = aes_cbc_encrypt(ptext, key, iv)
return ctext, ecb_mode
def main():
ecb_key, key = b"YELLOW SUBMARINE", make_aes_key()
ptext = aes_ecb_decrypt(loader("25.txt", "base64", split=False), ecb_key)
ctext = aes_ctr(ptext, key)
print(f"Cracking ciphertext using {CPUS} cores, please wait.")
# This signal handler business allows Ctrl-C to work more gracefully
# with multiprocessing. (Tested on Linux only.)
orig_handler = signal.signal(signal.SIGINT, signal.SIG_IGN)
with Pool(CPUS) as pool:
signal.signal(signal.SIGINT, orig_handler)
mp_data = ((ctext, key, offset) for offset in range(len(ctext)))
try:
recovered_ptext = bytes(pool.imap(mp_find_ptext_byte, mp_data))
except KeyboardInterrupt:
raise
else:
print()
print(recovered_ptext.decode())
finally:
print()
# Before you implement this attack, answer this question: why does CBC mode
# have this property?
#
import inspect
import os
import sys
sys.path.append(
os.path.dirname(
os.path.dirname(os.path.abspath(inspect.getfile(lambda: 0)))))
from util.aes_wrappers import aes_cbc_decrypt, aes_cbc_encrypt, make_aes_key
from util.text import repeating_key_xor
# Key and IV are both 128 random bits.
KEY = make_aes_key()
IV = make_aes_key()
PREFIX = b"comment1=cooking%20MCs;userdata="
POSTFIX = b";comment2=%20like%20a%20pound%20of%20bacon"
def make_userdata(bs):
userdata = bs.replace(b";", b"';'").replace(b"=", b"'='")
ptext = PREFIX + userdata + POSTFIX
return aes_cbc_encrypt(ptext, KEY, IV)
def is_admin(ctext):
if b";admin=true;" in aes_cbc_decrypt(ctext, KEY, IV):
return True
return False
def submit_random_ptext():
global KEY
KEY, iv = make_aes_key(), make_aes_key()
ptext = base64.b64decode(random.choice(B64STRS))
ctext = aes_cbc_encrypt(ptext, KEY, iv)
return ctext, iv