关键词: 信任，安全，串空间，点对点，无证书密码系统

Abstract: The open and anonymity nature of P2P networks makes it extremely susceptible to malicious users attacking.On way to minimize threats is to build the trust model for P2P network. The trust data is critical to the trust model of P2P system which validity is relied on the reliability of trust data. We presented a CL-PKGI3ased protocol which provides the ability for sharing trust data securely in the hybrid P2P networks. I}he protocol avoids the authentication of the public key and the key escrow problem of identity-based cryptosystem. The security of cryptosystem is based on Bilinear DifficHellman Problem. And the strand space model was used to prove that the secure protocol can achieve agrccmcnt properties and keep secrecy of trust data.

Key words: Trust, Security, Strand space, P2P, CL-PKC