TotalSecure Message Encrypter

ringzer0ctf

Task: Python2 encryptor seeds random.Random with a password and leaks 700 consecutive getrandbits(32) outputs before XOR-encrypting the message with the same generator. Solution: untemper the first 624 leaked outputs to clone the MT19937 state, advance the clone to the encryption position, regenerate the keystream and XOR it against the ciphertext to recover the plaintext without the password.