Defeating against Sybil-attacks in Peer-to-peer Networks

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. In this paper, we present a distributed protocol to reduce the adverse effects of sybil attacks in free riding problem. Our approach focuses on restricting nodes to obtain the number of service units in a reasonable level. Unlike other protocols, our protocol works well even if there are a large number of sybil nodes in the network. Our results show the promise of the protocol in limiting sybil attacks while not sacrificing application performance.