Subject: [dispatch] Proposal for a new WG: Privacy Enhanced RTP Conferencing (PERC)

From: Magnus Westerlund <[email-masked]>
Date: Wed, 25 Mar 2015 18:27:16 -0500

Dispatch,

AVTCORE WG has discussed a couple of proposals that discusses end-to-end
security in centralized RTP based conferences.

Drafts for these Proposals:
https://datatracker.ietf.org/doc/draft-jones-avtcore-private-media-reqts/
https://datatracker.ietf.org/doc/draft-jones-avtcore-private-media-framework/
https://datatracker.ietf.org/doc/draft-cheng-avtcore-srtp-cloud/

In these discussions one has reached the conclusion that this work
requires its own venue to continue the work. Therefore a number of
interested has put together a initial draft charter for a new WG.

Please review and provide feedback.

Name: Privacy Enhanced RTP Conferencing (PERC)
Area: ART
Chairs: TBD
Mailing List: <using [email-masked] for now>

Motivation for new WG
---------------------

RTP-based real-time multi-party interactive media conferencing is today
in widespread use. Many of the deployments uses one or more centrally
located media distribution devices that perform selective forwarding or
mixes media streams received from the participating endpoints. The media
transport protocol commonly used is RTP (RFC3550). There are various
signaling systems used to establish these multi-party conferences.

These conferences require security to ensure that the RTP media and
related meta data of the conference is kept private to the set of
invited participants and only other devices trusted by those
participants with their media.  At the same time, multi-party media
conferences do need source authentication and integrity checks to
protect against modifications, insertions or replay attacks.  Media
distribution devices supporting these conferences may also perform RTP
header changes and often consume and create RTCP messages for efficient
media handling.

To date, deployment models for these multi-party media distribution
devices do not enable them to perform their functions without having
keys to decrypt the participants’ media, primarily using Secure RTP
(RFC3711) to provide session security.

A new architecture model and related specifications is needed, with a
focused effort from the RTP and Security communities.

WG Objectives
-------------

This WG will work on a solution that enables centralized SRTP based
conferencing where the central device distributing the media is not
required to be trusted with the keys to decrypt the participant’s media.
The media must be kept confidential and authenticated between an
originating endpoint and the explicitly allowed receiving endpoints or
other devices.  Further it is desired that a solution still provide
replay protection so that the media distribution devices can’t replay
previous parts of the media.

The solution must also provide security for each hop between endpoints
and multi-party media distribution devices and between multi-party media
distribution devices. The RTCP messages and RTP header extensions
required for the media distribution device to perform the selective
media forwarding may require both source authentication and integrity as
well as confidentiality. The solution may also consider providing
end-to-end security for a subset of the RTCP messages or header extensions.

The solution should be usable from both SIP and WebRTC endpoints that
implement the extension defined by this WG.

This WG will perform the following work:

1.    Define a general architecture and RTP topology(s) that enables
      end-to-end media security for multi-party RTP conferencing.

2.    Define the trust model and describe the resulting security
      properties.

3.    Specify any necessary extensions to SRTP.

4.    Define a Key Management Function that distributes the keys. The
      system needs to be able to bind the media to the sender of the
      media’s identity and/or the identity of the conference.

Collaboration
-------------

If there is identification of missing protocols or functionalities, such
work can be requested to be done in another working group with a
suitable charter or by requests for chartering it in this WG or another
WG. Potential work that might require work in other WGs are DTLS
extensions (TLS) as well as RTP header extensions (AVTEXT). This
requires strong collaboration with the security area. We will notify
SIPREC, W3C WebRTC, AVTCore, and other related groups about this work.

Non-Goals
---------

The WG is not chartered to extend any signaling system used to establish
the RTP based conferences. It will however, need to consider in its
architecture how the solution may integrate with these systems.

Will not consider non-real-time usages, multicast based media
distribution, or Security descriptions-based keying.

Goals and Milestones
--------------------

TBD  Submit architecture or framework specification to IESG (Standards
Track)

TBD  Submit protocol specification(s) to IESG (Standards Track)

Cheers

Magnus Westerlund
(AVTCORE WG chair)

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