Sorcery: Could we make P2P content sharing systems robust to deceivers?

Deceptive behaviors of peers in peer-to-peer (P2P) content sharing systems have become a serious problem due to the features of P2P overlay networks such as anonymity, self-organization, etc. This paper presents Sorcery, a novel active challenge-response mechanism based on the notion that one side of interaction with dominant information can detect whether the other side is telling a lie. To make each client obtain the dominant information, our approach introduces social network to the P2P content sharing system; thus, the client can establish friend-relationships with peers who are either acquaintances in reality or those reliable online friends. Using the confidential voting histories of friends as own dominant information, the client can challenge the content providers with the overlapping votes of both his friends and the content provider, thus detecting whether the content provider is a deceiver. Moreover, Sorcery provides the punishment mechanism which can reduce the impact brought by deceptive behaviors, and our work also discusses some key practical issues. The experimental results illustrate that Sorcery can effectively address the problem of deceptive behaviors, and work better than the existing reputation models.