Mojtaba Bahrami - IT department, Amin Police University Tehran, Iran
Alireza Rahmani - Applied Research Center NAJA, ICT department Tehran, Iran
Behnam Dorostkar - Applied Research Center NAJA, ICT department Tehran, Iran

Session Initiation Protocol (SIP) is a key protocol in NGN signaling that is used during registration and session establishment. The protocol is also one of mains components of the IMS architecture. SIP authentication typically uses HTTP digest authentication, which is vulnerable to many forms of known attacks. in This paper at the first a detailed threat analysis of IMS is demonstrated then proposed a new approach for user authentication and server authentication by using Elliptic curve Diffie–Hellman (ECDH) and optional SIP’s header. Through our solution we can protect any network such as IMS network from intruders and eavesdropping. With present result, necessary steps for intruder to decode authentication is increased.

SIP Authentication, NGN, IMS, HTTP digest, Threat analysis