  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 employs classical secret sharing
and partially trusted intermediaries to provide arbitrarily high confidence in
the security of the protocol. Although certain failures elude detection, we
discuss preemptive strategies to reduce the probability of failure to an
arbitrarily small level: probability of such failures is exponentially
suppressed with increases in connectivity (i.e., connections per node).
