There is a new version of ZRTP available. Some major changes include:
- New title: ZRTP: Media Path Key Agreement for Secure RTP
- A new packet format. ZRTP now no longer uses RTP for transport.
Instead, it is a distinct protocol multiplexed on the same port as
RTP. The packet format is a similar structure to STUN, making it
clearly distinguishable from both RTP and STUN.
- Discussion of how ZRTP meets all ten requirements in
- Changed "a=zrtp" SDP attribute to "a=zrtp-zid" which allows
transport of ZID passed in ZRTP Hello message in the signaling for
coupling of media and signaling paths. Combined contents of old
"a=zrtp-sasvalue" into new "a=zrtp-sas" attribute.
- Changed Multistream mode to Preshared mode for a key agreement mode
which does not require a DH calculation.
- New method of calculating the SAS that protects against both MiTM
and bid-down attacks.
- New signature block allowing endpoints to sign the SAS and exchange
signatures in the Confirm messages.
- Definition of a new ZRTP RTP extension header field. No ZRTP data
is passed - the presence of the flag in RTP packets just indicates
support for the ZRTP protocol.
- Improved discussion about the behavior of media intermediaries in
media path keying.
Comments and suggestions are most welcome.
-------- Original Message --------
Subject: I-D ACTION:draft-zimmermann-avt-zrtp-03.txt
Date: Wed, 07 Mar 2007 10:50:02 -0500
A New Internet-Draft is available from the on-line Internet-Drafts
Title : ZRTP: Media Path Key Agreement for Secure RTP
Author(s) : P. Zimmermann, et al.
Filename : draft-zimmermann-avt-zrtp-03.txt
Pages : 53
Date : 2007-3-7
This document defines ZRTP, a protocol for media path Diffie-Hellman
exchange to agree on a session key and parameters for establishing
Secure Real-time Transport Protocol (SRTP) sessions. The ZRTP
protocol is media path keying because it is multiplexed on the same
port as RTP and does not require support in the signaling protocol.
ZRTP does not assume a Public Key Infrastructure (PKI) infrastructure
or require the complexity of certificates in end devices. For the
media session, ZRTP provides confidentiality, protection against Man
in the Middle (MITM) attacks, and, in cases where a secret is
available from the signaling protocol, authentication. ZRTP can
utilize two Session Description Protocol (SDP) attributes to provide
discovery and authentication through the signaling channel. To
provide best effort SRTP, ZRTP utilizes normal RTP/AVP profiles.
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