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[Linphone-developers] Integrating ZRTP protocol into LINphone

From: Earl
Subject: [Linphone-developers] Integrating ZRTP protocol into LINphone
Date: Sun, 25 Jan 2009 13:07:31 +0100
User-agent: Thunderbird (Windows/20081105)

On Sat, 24 Jan 2009, Earl wrote:

I am thinking about open-source standards, which Zphone is ( IETF ).
It is the only protocol that I know of that can resist man-in-the-middle attacks.

Hmm, please post a link for the ZRTP RFC, I can't find it...

Doing a Google search for the words:  zrtp ietf
gives *357 000 results

I quote:

     Here's what we last submitted to the IETF

The ZRTP Internet Draft as last submitted on the IETF web site:

   * **
     This link also contains older obsolete drafts that can be
     individually selected at the top of the page, and colorful tools
     to review the changes between drafts.

On our own web site, the submitted draft is also available:

   * *HTML*
     - Nicely formatted and easier to read than the format used on the
     IETF web site.

The ZRTP draft is still undergoing changes, the last only 10 days ago.
It may not yet have a RFC, don't know.
I believe the SRTP standard says very clearly in it that SRTP offers zero security.

What are you talking about??? SRTP does not get into key exchange, that is for other protocols to deal with. Even draft-zimmermann-avt-zrtp-12 runs over SRTP!!! Nathan Stratton

That is exactly what I said in my last email:
"Actually Zphone uses SRTP, but in a secure fashion.
SSL/TLS does not warn you that there is a MITM, Zphone can
warn you. "

You said:
"May want to think about standards based SRTP rather
then the Zphone stuff... "
But now you say ZRTP uses standards based SRTP.

It is clear that SRTP can provide zero security, since SRTP
has no secure way to exchange keys.

Other protocols must be used for key exchange, but the
big problem is that no known public key exchange can
resist the MITM.

For this reason, ZRTP uses a verbal SAS exchange, since
its Diffie-Hellman key exchange can also be trivially
broken just like all others, including SSL/TLS.

The very fact that a verbal SAS exchange can discover
the MITM existence will discourage this listening, since
MITM do not like to be exposed.  This verbal SAS exchange
makes ZRTP the "gold standard" for voice and video

Nathan, if you would take the time to read about ZRTP, you
would understand why it is fast becoming a de-facto security
standard for RTP.  The Linux SIP program TWINKLE is using
it internally, rather than an external Zphone.  SIP-
Communicator has also internally integrated it into its code.
At the FOSDEM in Brussels (7-8 février /2009/) there should
be an interop demo between TWINKLE and SIP-COMMUNICATOR
both using internal ZRTP protocol.

Simon, I started this thread asking you to assure the correct
functioning of the external Zphone program.
I would now like to politely ask you to please contact Phil
Zimmermann and tell him that you wish to integrate the ZRTP
protocol into the LINphone code.  Phil could allow you
confidential access to the latest ZRTP builds thereby
permitting LINphone betas to have the latest ZRTP build and
code.  Phil has a good relationship with a number of open
source developers.

Simon, I am assuming that you desire to have excellent security
for voice and video integrated into LINphone.  If not, I am
on a faux piste.

Regards, Earl

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