Sip Messages Based On The S / Mime Security Mechanism

In recent years, session initiation protocol (SIP) is gotten more attention in the research fields of communication and network, is one of core protocols for Next Generation Network (NGN). SIP is an application-layer control protocol that can establish, modify, or terminate user sessions.When organizations are starting to apply SIP to conduct their core business, security of SIP becomes clearly critical. Security problem is complex, and security of SIP Services is very important. There are such regularly SIP secure mechanisms as TLS, IPSec, SIPS URI, HTTP and S/MIME. The secure mechanisms can be the same with different SIP secure requirements, but also have some deficiencies of each side. So they must be improved to assure security of SIP.In this paper, we mainly study the secure mechanisms of SIP. On the works of research, firstly, We study the systematic configuration of SIP; Secondly, We review security requirements of SIP, especially study SIP secure mechanisms based on S/MIME; Thirdly, we put forward a secure mechanism based on S/MIME which inducted PKCS, and discuss S/MIME encryption procedure in SIP. Finally, as an example for a practical project, we realized an instant messaging system based on SIP protocol, and used S/MIME which inducted PKCS to encrypt SIP entity, so as to improve traditional encryption mode.