In this paper, a novel authentication protocol called APExSPKI for P2P networks is proposed with the combination of certificate and trust. Trust being bound to certificate allows peers to perform authorization and access control as well as authentication. In addition, APExSPKI avoids the presence of central trusted authorities and allows every peer in the community to participate in the trust recommendation and be an agent to issue certificates for other peers, which fully embodies the equity and self-government of peers.