| With the development of information technology, the framework of distributed computing is under a new revolution, among which Peer-to-Peer (P2P) technology is seen as a promising one. As there are vicious peers that arouse many attacks preventing network from running normally, Peer-to-Peer technology brings us both opportunities and threats. How to identify, restrict and put end to those vicious peers is becoming a hotspot. And the research on peers' reputation has brought more and more attention. Because trustworthiness of each other is the precondition of business, reputation can represent whether the peer's foregone behavior is suitable to participate in the network community.This paper first introduces interrelated knowledge about network security and cryptology, and then analyzes the characteristic, advantage and research actuality of P2P technology. The author combines the advantages of Chord model and P2P network and puts forward a hierarchical P2P model: Dual-Chord. The Chord-model-based system is used for peers' resource locating and lookup. It consists of main net and subnet. This topology both maintains good quality of DHT and considers the peers' difference of trustworthiness, which means the more trusty peers in network can get more important topology position, and make more contribution to topology stability and reliability.As a foundation of the above, this paper puts forward a trust model based recommendation value and makes improvement on it. In the improved model, we consider sufficiently about the trustworthiness of a peer itself which affords recommendation value. This model conquers the insecurity of setting up some peers with high trustworthiness in advance. What's more, we take separate storage of peer's trustworthiness into account and use Public-Key-Infrastructure (PKI), which can prevent the peer from deceiving by reworking its trustworthiness. The text classifies in detail about peer's vicious behavior, that's because different vicious behavior affects differently to the network. For example, putting out vicious codes is more serious than downloading slowly. We can calculate more scientific trustworthiness in this way. Through analysis, we know this model can restrain the conduct of cheating and imitating. Experiment result proves that when the number of vicious peers has reached a definite proportion, the improved algorithm can keep a higher successful download. |
