The anonymity of an almost fair chaum mix

The first-come-first-serve fair queuing algorithm for a router is known to minimize the per packet delay in a single server queue. The policy however, provides no user anonymity to transmitted packets; mere observation of transmission times can reveal the source of every transmitted packet. The information-theoretic analysis of the anonymity of queuing policies under a relaxation of the First-come-first-serve fair queuing is considered in this work. An entropy-based metric of anonymity is proposed to quantify the anonymity of queuing policy under a fairness relaxation where each packet from a user can be transmitted ahead of at most one packet from another user sharing the mix. Inner and outer bounds on the maximum achievable anonymity are characterized as functions of the available memory at the mix.