#!/usr/bin/env pypy3

import os
from pydoc import plain
from sys import byteorder
from Crypto.Cipher import AES
from Crypto.Util import Counter
import hashlib

# Create a secret.py file with a variable `FLAG` for local testing :)
from secret import FLAG

secret_key = os.urandom(16)

def encrypt(plaintext, counter):
    m = hashlib.sha256()
    m.update(counter.to_bytes(8, byteorder="big"))

    alg = AES.new(secret_key, AES.MODE_CTR, nonce=m.digest()[0:8])
    ciphertext = alg.encrypt(plaintext)

    return ciphertext.hex()


def main():
    print("DES is broken, long live the secure AES encryption!")
    print("Give me a plaintext and I'll encrypt it a few times for you. For more security of course!")

    try:
        plaintext = bytes.fromhex(input("Enter some plaintext (hex): "))
    except ValueError:
        print("Please enter a hex string next time.")
        exit(0)
    
    for i in range(0, 255):
        print(f"Ciphertext {i:03d}: {encrypt(plaintext, i)}")
    
    print("Flag:", encrypt(FLAG.encode("ascii"), int.from_bytes(os.urandom(1), byteorder="big")))

if __name__ == "__main__":
    main()