Auditable Privacy: On Tamper-evident Mix Networks

Authors: J.Y. Choi, P. Golle and M. Jakobsson.

We introduce the notion of tamper-evidence for mix networks in order to defend against attacks aimed at covertly leaking secret information held by corrupted mix servers. This is achieved by letting observers (which need not be trusted) verify the absence of covert channels by means of techniques we introduce herein. Our tamper-evident mix network is a type of re-encryption mixnet in which a server proves that the permutation and re-encryption factors that it uses are correctly derived from a random seed to which the server is committed.