We show how QKD on a multi-user, multi-path, network can be used to establish a key between any two end users in an asynchronous fashion using the technique of bit-transport. By a suitable adaptation of our previous secret-sharing scheme we show that an attacker has to compromise all of the intermediate relays on the network in order to obtain the key. Thus, two end users can establish a secret key provided they trust at least one of the network relays.
@article{arxiv.1203.4046,
title = {Asynchronous QKD on a Relay Network},
author = {S. M. Barnett and S. J. D. Phoenix},
journal= {arXiv preprint arXiv:1203.4046},
year = {2012}
}