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#!/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()
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