Privacy and Liveliness for Reputation Systems

Privacy-respecting reputation systems have been constructed based on anonymous payment systems to implement raters' anonymity for privacy-respecting reputation systems. To the best of our knowledge, all these systems suffer from the problem having a " final state " , that is a system state in which users have no incentive any longer to behave honestly , because they reached a maximum reputation or they can no longer be rated. Thus the reputation is in fact no longer lively. We propose a novel approach to address the problem of liveliness by the introduction of negative ratings. We tie ratings to actual interactions to force users to also deposit their negative ratings at the reputation server. Additionally we enhance raters' anonymity by limiting timing attacks through the use of transferable-eCash-based payment systems.