A Proxy-Based Server Irrelevant Security Mechanism for VoIP

With the development of Internet, people can use their computer to make calls instead of telephone. Many Internet calls take place without any protection. TLS and SRTP could keep the callee and caller from third party´s malicious action. However, both methods could do little when the reliability of VoIP server is under suspicion. In this paper, we present a server irrelevant security mechanism for VoIP system based on SIP and RTP. This mechanism implements safety handshake in media channel. User gets certificate from third party CA. Caller and callee exchange PKI or IBE information during the call. As long as the server keeps media data unchanged, this mechanism could ensure the safety of the call against server eavesdropping. It is flexible because the user could utilize different CA to obtain suitable safety demand with the same VoIP server. Cooperating with other protective methods, it can provide a more reliable environment for Internet telephone.