def main() -> None:
with open("data/25.txt", "r") as f:
c = b64decode(f.read())
k = b"YELLOW SUBMARINE"
cypher = AES.new(k, AES.MODE_ECB)
plaintext = cypher.decrypt(c)
cyphertext = aes_ctr(plaintext, RANDOM_KEY)
rarw_plaintext = break_rarw(cyphertext)
assert rarw_plaintext == plaintext
print(rarw_plaintext.decode())
def bulk_ctr(cyphertexts: list[bytes]) -> list[bytes]:
return [aes_ctr(e, RANDOM_KEY) for e in cyphertexts]
def edit(cyphertext: bytes, key: bytes, offset: int, new_text: bytes) -> bytes:
plaintext = aes_ctr(cyphertext, key)
plaintext = plaintext[:offset] + new_text \
+ plaintext[offset + len(new_text):]
return aes_ctr(plaintext, key)
def is_admin(cyphertext: bytes) -> bool:
plaintext = aes_ctr(cyphertext, RANDOM_KEY)
return "admin=true" in plaintext.decode(errors="replace")
def oracle(userdata: bytes) -> bytes:
prefix = b"comment1=cooking%20MCs;userdata="
postfix = b";comment2=%20like%20a%20pound%20of%20bacon"
userdata = userdata.replace(b";", b"").replace(b"=", b"")
plaintext = pkcs7(prefix + userdata + postfix)
return aes_ctr(plaintext, RANDOM_KEY)
def bulk_ctr(f):
return [aes_ctr(e, RANDOM_KEY) for e in f]
def ctr_oracle(plaintext: bytes) -> int:
"""Stream cipher compression oracle"""
key = get_random_bytes(BLOCKSIZE)
return len(aes_ctr(compress(format_request(plaintext)), key))