Abstract
Session initiation protocol (SIP) provides the basis for establishing the voice over internet protocol sessions after authentication and exchanging signaling messages. SIP is one of the significant and extensively used protocols in the multimedia protocol stack. Since the RFC2617 was put forth, numerous schemes for SIP authentication have been presented to overcome the flaws. Recently, in 2012, Tang and Liu proposed SIP based authentication protocol and claimed for eliminating the threats in Arshad and Ikram protocol. However the scheme can be made more robust by making further improvements, as the former scheme may come under a threat by adversaries through impersonating a server, given that the user password is compromised. We have proposed an improved protocol for SIP authentication by using elliptic curve cryptography that encounters the previous threat with enhanced security. The analysis shows that proposed scheme is suitable for applications with higher security requirements. Copyright (c) 2013 John Wiley & Sons, Ltd.