href="http://scm.sipfoundry.org/rep/ietf-drafts/fluffy/draft-ietf-sipping-certs-01.html"
target="NewWindow">draft-ietf-sipping-certs-01

This draft defines a Credential Service
that allows SIP User Agents to use a SIP package to discover the certificates
of other users. This mechanism allows user agents that want to contact a given
Address-of-Record (AOR) to retrieve that AOR’s certificate by subscribing to
the Credential Service. The Credential Service also allows users to store and
retrieve their own certificates and private keys.