Session Initiation Protocol
SIP [171,169,170] is a text-based protocol, similar to HTTP and SMTP, for initiating interactive communication sessions between users. Such sessions include voice, video, chat, interactive games, and virtual reality. Due to the complexity of the protocol, many distinct mechanisms have been proposed to secure different aspects and usages of SIP. We will concentrate on the most common ones, Protocol SIP-Digest (4), (see [171], Section 22) re-uses the seurity mechanisms developed for HTTP.
Protocol SIP-Digest should provide Authentication (G1,2).
For Protocol SIP-SMIME (5), defined in Section 23 of the same RFC [171], we assume the existence and provision of user certificates.
Protocol SIP-SMIME should provide Authentication and Secrecy (G1,2,12) (more explicitely: User-to-User Authentication, User-to-User Content Secrecy, and Proxy-to-User Authentication).
Related RFCs and drafts are: [134], [149], [202], [92], [16], [27], [62], [112], [154], [155], [153], [110], [197], and [200].