Subject: [AVT] I-D ACTION:draft-ietf-avt-srtp-06.txt

From: [email-masked]
Date: Thu, 01 May 2003 07:48:19 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Audio/Video Transport Working Group of the IETF.

	Title		: The Secure Real-time Transport Protocol
	Author(s)	: M. Baugher et al.
	Filename	: draft-ietf-avt-srtp-06.txt
	Pages		: 53
	Date		: 2003-4-30
	
This document describes the Secure Real-time Transport Protocol   
(SRTP), a profile of the Real-time Transport Protocol (RTP), which 
can provide confidentiality, message authentication, and replay 
protection to the RTP/RTCP traffic.

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From: Mark Baugher <[email-masked]>
Date: Fri, 02 May 2003 09:52:43 -0700

Hello,

We have prepared this version of the I-D for the IESG review.  It contains 
the following changes, most of which are what we said we were going to do 
in the foil presented to the last AVT WG meeting.

1. Authentication tag length

# Made 80-bit SRTP authentication the default
# Crafted precise language about when a NULL (zero length)
or short (e.g. 32-bit) SRTP authentication tag
is acceptable and its elaborated the risks
# Added text describing replay attacks

For the above, Section 7.5 has been added, and Section 9.5 has
been extended.

# Mandated 80-bit SRTCP authentication
# Removed "error tolerance" from the spec (i.e. we eliminated
non-propagation of bit errors from the goals)
# Mandated automatic key generation/management

2. Reflect recent feedback from programmers

# Clarifications on re-keying, i.e. the use of the <From, To> vs MKI
(Section 8.1: the <From, To> to be used in simple scenarios, MKI recommended)

# The master key sharing is allowed only within the same RTP session
(before was allowed also between RTP sessions, but that caused complexity
due to the risk of SSRC collision and two-time pad)

3. Fixed a mistake

Changed the length of the authentication session key for HMAC/SHA1
from 128 to 160 bits (to conform to RFC 2104 recommendations)

4. Cleaned up

Scenarios (section 11) cleaned up.

Some language fixing (e.g. variable -> configurable, some mandatory --> 
recommended).

Mark

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_______________________________________________
Audio/Video Transport Working Group
[email-masked]
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From: Allison Mankin <[email-masked]>
Date: Wed, 07 May 2003 18:19:00 -0700

Folks,

I plan to Last Call SRTP, having done a long security and AD review on
version 05, resulting in a number of the changes that Mark describes.
So far I have seen no list discussion of his mail, but if working group
issues do come up, I suggest we take them in parallel with the IETF
Last Call, and if extra time is needed, that is ok.

Allison