Resisting Sybils in Peer-to-peer Markets.

We describe two techniques for reducing the effectiveness of sybil attacks, in which an attacker uses a large number of fake user accounts to increase his reputation. The first technique uses a novel transformation of the ranks returned by the PageRank system. This transformation not only reduces susceptibility to sybil attacks but also provides an intuitive and easily interpreted reputation score. The second technique, called RAW, eliminates remaining vulnerabilities and allows full personalization of reputations, a necessary condition for a sybilproof reputation system.