Subject: [AVT] Security issues for draft-ietf-avt-rtcpssm

From: Julian Chesterfield <[email-masked]>
Date: Mon, 24 Jun 2002 14:59:32 -0700

Further to discussions at the last IETF meeting, more consideration has
been given to the unicast RTCP feedback draft security issues,
particularly with respect to source authentication of RTCP streams. This
has been identified as an issue that must be addressed in order for
unicast feedback to be standardised for contexts such as SSM groups and
related single source environments.

It didn't seem appropriate to release an `official' document on the
subject at this stage, however in order to illustrate the problems and
work towards a solution, I have put some thoughts down into an analysis
document in order to outline some options and generate discussion
amongst interested parties.

This document therefore is available from:

http://irg.attlabs.net/rtcp_ssm/rtcp_security.ps    (postscript) and
also as

http://irg.attlabs.net/rtcp_ssm/rtcp_security.pdf   (pdf)

I would greatly appreciate comments and feedback on the ideas presented,
with the intention that a solution can be integrated into the exisiting
draft, or released as a separate profile to accompany the unicast
feedback document.

Many Thanks,

Julian Chesterfield

============================
A brief synopsis of the main points:

- Security requirements identified in draft-ietf-avt-rtcpssm-00, section
11. Key requirement, however is unique source authentication.

- Description of some existing IETF security solutions and accompanying
key distribution mechanisms.

- TESLA style authentication identified as the best lightweight solution
out of options presented.

- Proposal to adopt TESLA with some modifications in order to enable
time synchronisation, fixed key disclosure interval and alternative
feedback address identification.

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Colin Perkins <[email-masked]>
Date: Sun, 30 Jun 2002 13:17:24 -0400

Julian,

Interesting document, I think it clearly shows the problems in ensuring
security for a complete one-to-many media distribution system. I wonder,
though, if the problem might become clearer if split into two parts: the
issues that are specific to unicast feedback and those that are relevant
for any one-to-many transmission? 

Unicast feedback would seem to cause two additional security issues: (1)
identification of where to send feedback; and (2) authentication of RTCP
traffic from the sender, so receivers know how much feedback to send. The
other issues, confidentiality of the media, replay protection, authenticity
and integrity of the media, are important but do not seem specific to the
unicast RTCP feedback case.

A way to move forwards might be to solve the problems caused specifically
by unicast feedback - making something that is no worse than the existing
protocols - and leave the broader issues for future study. 

Colin