Embodiments of the present invention disclose a peer enrollment method, a route updating method, a communication system, and relevant devices to improve security of a peer-to-peer (P2P) network. The peer enrollment method includes: receiving an enrollment request from a peer, where the enrollment request carries identity information of the peer; verifying the identity information of the peer, and if the verification succeeds, obtaining peer location information of the peer and generating a peer credential according to the peer location information; and sending the peer credential carrying the peer location information to the peer so that the peer joins the P2P network according to the peer credential. Embodiments of the present invention further provide a route updating method, a communication system, and relevant devices. Embodiments of the present invention may improve security of the P2P network effectively.