Key generation with a Byzantine helper

This paper considers the problem of key generation with a helper, which might be subjected to Byzantine attacks. If the helper is not under attack, it will follow the key generation protocol. However, if the helper is under attack, it will modify the messages to mislead the key generation parties. We propose a scheme that can benefit from the helper, if the helper is not under attack, and can detect the presence of the attack, if the helper is under Byzantine attacks. We show that our key generation scheme can achieve the secret key capacity when the helper is not under attack. At the same time, if the helper is under Byzantine attacks, our scheme can achieve the key rate as if the attacker is a passive eavesdropper.