In peer-to-peer (P2P) systems, peers often must interact with unknown or unfamiliar peers without the benefit of trusted third parties or authorities to mediate the interactions. A peer will need reputation mechanisms to incorporate the knowledge of others to decide whether to trust another party in P2P systems. This paper discusses the design of reputation mechanisms and proposes a novel distributed reputation mechanism to detect malicious or unreliable peers in P2P systems. It illustrates the

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... process for rating gathering and aggregation and presents some experimental results to evaluate the proposed approach. Moreover, it considers how to effectively aggregate noisy (dishonest or inaccurate) ratings from independent or collusive peers using weighted majority techniques. Furthermore, it analyzes some possible attacks on reputation mechanisms and shows how to defend against such attacks.