A Group-Based Trust Metric for P2P Networks: Protection against Sybil Attack and Collusion

Though reputation-based trust mechanism is optimal for stimulating peers to cooperate in P2P networks, it cannot avoid facing some malicious attacks. In this paper we investigate the characteristic of P2P reputation networks and propose a group-based trust metric to alleviate the effects of Sybil attack and collusion. The CNM algorithm is used to divide the whole network into some trust groups and show the relationship between them. Our trust metric contains factors of the relationship between trust groups, the degree of the peer, and the similarity between the neighbors of the peer. We evaluate the metric and show that the effects of the Sybil attack and collusion can be alleviated effectively.