Technical Summary
The existing security mechanisms in the Session Initiation Protocol
are inadequate for cryptographically assuring the identity of the end
users that originate SIP requests, especially in an interdomain
context. This document specifies a mechanism for securely identifying
originators of SIP messages. It does so by defining two new SIP
header fields, Identity, for conveying a signature used for
validating the identity, and Identity-Info, for conveying a reference
to the certificate of the signer. It specifies the mechanisms and
procedures for using these and how they can be used with the
existing SIP privacy capabilities.
It is desirable for SIP user agents to be able to send requests to
destinations with which they have no previous association - just as
in the telephone network today, one can receive a call from someone
with whom one has no previous association, and still have a
reasonable assurance that their displayed Caller-ID is accurate. A
cryptographic approach, like the one described in this document, can
probably provide a much stronger and less-spoofable assurance of
identity than the telephone network provides today.
Working Group Summary
This specification required a number of tries and much analysis.
There was strong consensus on the solution by the time it reached
the version in this draft.
Protocol Quality
Eric Rescorla provided early architectural review of the work.
The careful reading by the GEN-ART reviewer, Lakshminath
Dondeti was valuable. Allison Mankin is the Responsible Area Director.