Building trustvvorthy sjervices in p2p networks

Abstract

Building trust is a rnajor concern in Peer-to-Peer networks as several kinds ofapplication rely on the presence of trusted services. However, the presence of untrusted peers rnay hinder the robustness and degrade the overall performance of applications. Untrusted nodes in the network rnay be faulty, rnalicious, selfish, or even act together to attack the application. Traditional techniques for countering untrusted node activity do not scale, produce very high overhead, or rely on unrealistic assurnptions. This thesis airns to provide a frarnework to build trustworthy applications over structured Peer-to-Peer networks. We describe and evaluate both a reputation systern and a rnernbership algorithrn which builds a cornrnunity of reputable peers. Our reputation systern introduces the concept of risk to rnake applications aware of several rnalicious node behaviours. We propase a risk rnetric that cornplernents the reputation value and show that it significantly reduces the nurnber of rnalicioustransactions. We propose a new rnernbership algorithrn to build a scalable pseudo-trusted ringwithin a Distributed Hash Table. Our algorithrn uses a reputation-based approach to decide whether a node can participate to the ring. We dernonstrate the benefits of this approach, present sorne exarnple applications and evaluate how rnuch it irnproves the reliability of a trusted routing service.