Abstract: Effective trust mechanism for P2P networks needs to be constructed to isolate malicious peers and guarantee successful completion of transactions between peers against multiple network attacks. Considering the characteristics of behaviors of peers and the importance of negative evaluation, trust mechanism based on negative evaluation dissemination is proposed. Once a transaction is evaluated negatively, the information of the negative evaluation will be disseminated to related peers which have completed transactions in a certain period of time with the upload peer. The impact of negative evaluation on the reputation of peer is enhanced. The reputation value of the peer after computed twice can reflect the actual reputation level and the trends of transactions of the peer. Simulations are given and the results show that the trust mechanism can guarantee the success rate of transaction completion and defend against attacks effectively.

Key words: trust mechanism, negative evaluation dissemination, Peer-to-Peer（P2P） networks, collusive attack, swing attack

摘要： 面对各种网络攻击，P2P网络需要有效的信任机制隔离恶意节点，保证节点的成功交易。考虑节点行为特征和差评的重要性，提出基于差评散布的信任机制。服务节点一旦提供的服务被给出差评，对其近期交易的相关节点进行差评的散布，加大差评对服务节点声誉的影响力度。经过二次计算的节点声誉值能真实反映节点近期的声誉水平与交易趋势。实验结果表明，该信任机制能保证正常节点的交易成功率，有效对抗各种攻击行为。

关键词: 信任机制, 差评散布, 点对点（P2P）网络, 合谋攻击, 摇摆攻击