crypto

Semantic Security

Punkty: 304

Rozwiązań: 10

It's not cryptographically secure random, but I think it's good enough.

nc semantic.ecsc24.hack.cert.pl 5102

import binascii
import random


def xor(*t):
    from functools import reduce
    from operator import xor
    return [reduce(xor, x, 0) for x in zip(*t)]


def main():
    flag = open("flag.txt", 'rb').read()
    while True:
        print("1. Get ciphertext")
        print("2. Exit")
        choice = input(">").strip()
        if choice == "1":
            keystream = [random.randrange(0, 255) for _ in range(len(flag))]
            random.shuffle(keystream)
            print(binascii.hexlify(bytes(xor(flag, keystream))).decode())
        elif choice == "2":
            return
        else:
            print("WTF?")


if __name__ == "__main__":
    main()

Format flagi: ecsc24{litery_cyfry_i_znaki_specjalne}.
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