Based File Sharing System For Credit Evaluation System Design And Realization

Nowadays, the Peer-to-Peer (P2P) is one of the most hotpots in the computer network,and it strongly affects the traditional network, which focuses on its content. While P2P network adopts a distributing network structure, and each peer is both client and server. This infrastructure is widely used in file-sharing, distributed computation,cooperation system, electrical business, deep search engine, etc. But P2P network is still evolution, it has not general standard. Its security should be paid special attention because of its distributed infrastructure. The P2P file-sharing system offers a way for users to exchange their resources easily, but the truthfulness of the resources cannot be guaranteed. The openness and anonymity character of P2P file-sharing permits each peer to join and leave the community, some vicious peers may harm the system,which enhances the unsafe probability in file-sharing, so it is necessary to take some measures to distinguish and reduce the effects of vicious peers.By analyzing several solutions of P2P network security and the evaluation system of real life,this paper designs a credibility evaluation system based on the contents and the node evaluation. This system will be made an independent evaluation for each document, which can be used to describe the authenticity of the document when downloading by other nodes.System get the credibility of other nodes by calculating the volume of evaluation, length of online time, bandwidth and other factors,which can judge node`s credibility. Through the analysis of this evaluation system shows that the system is correct, feasibility.Then this thesis designs and realizes a file sharing system based on Distributed Hash Table(DHT),to use this credibility evaluation system.Then improved the structure of DHT to adapt to this evaluation system. To prevent other nodes from malicious node, the system limits the connectivity from malicious node, control malicious node`s upload and download operation to ensure that P2P file-sharing system is in the accuracy of resources and authenticity.