Abstract: Although current existing trust model reduces the impact of peers' malicious attack in P2P system, these repir tation systems do not concern with reducing free riders in P2P networks,namely,peers with high trust value tansform to free riders. Because lots of free riders exist, robust and avaliable of P2P system arc degraded. So, a trust model based on time slots was designed,and the nearer time from now the greater time slot's weight was gaven. Theoretical analysis and simulation show that this proposal not only prevents peers with high trust value to free riders, but also limits peers to make malicious attack recently, and peers' trust value arc more and more bight in compared with other proposals.

Key words: Trust model, Peer reduction, Free rider, P2P networks, Malicious attack