Overview
Message file is encrypted with repeating-key XOR using key string encrypt.
Reconnaissance
Apply inverse XOR using key encrypt across message bytes.
Exploitation Strategy
XOR ciphertext bytes sequentially with key index: data[i] ^ key[i % len(key)].
Solution Code
key = b"encrypt"
data = open("message.bin", "rb").read()
print(bytes(d ^ key[i % len(key)] for i, d in enumerate(data)).decode())Flag
hwj{this_is_next_level_encryption}