Distributed authentication for randomly compromised networks

We introduce a simple, practical approach with probabilistic information-theoretic security to solve one of quantum key distribution's major security weaknesses: the requirement of an authenticated classical channel to prevent man-in-the-middle attacks. Our scheme uses classical secret sharing techniques and partially trusted intermediaries and provides arbitrarily high confidence in the security of the protocol. Our protocol has the drawback that users are unable to detect some types of failures, although they can take preemptive measures to make the probability of failure arbitrarily small. Increased security is achieved with modest increases in resource costs.