A Lightweight Scheme for Securely and Reliably Locating SIP Users Lei Kong Vijay A. Balasubramaniyan Mustaque Ahamad Introduction Mapping SIP address to contact address is an important function in VOIP systems Key requirements: Integrity Availability Performance and scalability Our solution Lightweight scheme to meet these requirements SIP Trapezoid Related Work SIPS DNS security extension Authentication Service Others Our Approach Proxies have certificates User contact address signed with locally generated public key SIP proxies protect user public key exchange Balancing between two extremes: PGP/SSH End user certificates Other SIP message fields can also be protected Using SIP Infrastructure to Protect User Public Key Exchange Proxy awareness of user public keys User public key is registered with local proxies User public key is completely managed by end points Initial Session Setup Session Setup after Public Key Exchange High Availability Via Replication Byzantine fault model Replication schemes For stateful proxy Consistency requirement For stateless proxy Optimistic assumption and parallel session setup Stateful Example Stateless Example Preliminary Evaluation Conclusions and Future Work Lightweight approach for securing contact address and other SIP message fields Availability with Byzantine failure Preliminary performance results show better scalability Future performance study and SIP extension RFC proposal