摘要： 由于P2P系统具有分布性、开放性等特点，传统的访问控制和认证的方法不能很好地在P2P系统中适用。一些专门解决P2P系统中的信任问题的声誉系统也存在着容易被虚伪的节点所攻击的缺陷。文章研究了自动信任协商机制如何通过互相出示证书的方法合理地解决了P2P系统中的访问控制和认证问题，针对自动信任协商中存在策略循环依赖的问题使用建立LTTP的方法加以解决，并通过模拟实验证明LTTP的确能够提高信任协商的成功率。

关键词: 信任, 声誉系统, 自动信任协商, 策略循环依赖, 局部可信第三方

Abstract: As P2P system is inherently decentralized and open, some traditional access control and authentication approaches cannot be adapted in P2P system. Some reputation systems which aim to solve the trust problem in P2P system may be easily attacked by some hypocritical peers. This paper researches on automated trust negotiation mechanisms which use exchanging credentials to completely solve the access control and authentication problems in P2P systems, builds LTTP to solve the cyclic interdependent policies problem in ATN, experiments prove that LTTP can improve the success rate of ATN.

Key words: Trust, Reputation system, Automated trust negotiation, Cyclic interdependent policies, Local trusted third party