Taxonomy of attacks and defense mechanisms in P2P reputation systems—Lessons for reputation system designers

Robust and credible reputation systems are essential for the functionality of Peer-to-Peer (P2P) applications. However, they themselves are susceptible to various types of attacks. Since most current efforts lack an exploration of a comprehensive adversary model, we try to fill in this gap by providing a thorough view of the various credibility threats against a decentralized reputation system and the respective defense mechanisms. Therefore, we explore and classify the types of potential attacks against reputation systems for P2P applications. We also study and classify the defense mechanisms which have been proposed for each type of attack and identify conflicts between defense mechanisms and/or desirable characteristics of credible reputations systems. We finally propose a roadmap for reputation system designers on how to use the results of our survey for the design of robust reputation systems for P2P applications.