Abstract: P2P system can enable the nodes that are strangers to one another to make online transactions with each other，but the problem of security is attracting more and more people’s attention.Hence，how to construct an effective trust mechanism to help build trust among the nodes is an important issue for the research of P2P technology nowadays.This paper proposes a novel reputation-based trust evaluation mechanism for P2P system.This mechanism takes into account the comprehensive factors affecting the trust level，improves the calculation methods of the local reputation and global reputation，reduces the computing load of the trust level，and introduces the blacklist mechanism into P2P system.The experiment result shows that this proposed mechanism can effectively evaluate the trust level of node and detect and separate the malicious nodes from P2P system to improve the rate of successful transaction，and can be effectively applied to P2P system.

Key words: P2P（Peer to Peer） system, reputation, trust mechanism

摘要： P2P系统能够使陌生节点之间进行在线交易，但安全问题越来越受到人们的关注。因此，如何在P2P系统中构建一个有效的信任机制来帮助在节点之间建立信任是目前P2P技术研究的一个热点。提出了一种新的P2P系统中基于声誉的信任评估机制，该机制较全面地考虑了影响信任度的因素，改进了局部声誉与全局声誉的计算方法，降低了信任度的计算负载，并且引入了黑名单机制。实验结果表明，该机制能有效地评估节点的信任度，识别和隔离恶意节点，提高系统交易成功率，并能有效地应用于P2P系统中。

关键词: P2P系统, 声誉, 信任机制