earticle

영어

Peer-to-Peer networks have become a popular way for users to share files over the Internet.However, there has been a spurt of works showing that the existence of sybil attacks is a serious threat to Peer-to-Peer networks, where one or more attackers can forge a large number of fictitious identities. Implementing correct protocols to address sybil attacks is the key to improving the performance.In this paper, we present a novel systemto defend against Sybil attacks.Our direct and indirect transaction protocols limit the number of service units that a node can obtain.Furthermore, we design a dynamic reputation ranking algorithm for the indirect transaction protocol.Combining these two, a node with a high priority has more probability of obtaining service.Our system does not try to prevent users from creating multiple identities, but they cannot gain extra profit from doing so.It achieves a provable performance and overcomes the limitation of current social network-based defenses.Simulation results show that our system achieves a provable bound in terms of the number of service units obtained by sybil nodes while not sacrificing the performance of the file sharing application.