sip101 This document specifies a means to integrate Certificate Management Service for The Session Initiation Protocol(SIP) with presence. Presentities employing the Presence Information Data Format (PIDF) can use the extensions in this draft to advertise their ability to exchange signalling using S/MIME, and thus allow secure signalling between the two peers. In a presence application, the presence of this information could be displayed to watchers as the padlock "secure signalling available" of the presentity.