[VOIPSEC] ZRTP and Asterisk

[Dittmann, Werner (NSN - DE/Munich)]

Alejandro,

as you said I use Twinkle+ZRTP only in Clinet-to-Client connections
and also via SIP proxies. I've no experience with Asterisk. Also
The ZRTP library that Twinkle uses does _not support_ the specific
Asterisk mode as defined by the ZRTP specification. Thus my
interpretation is that Asterisk just forwards the data send over
the RTP session without doing any modification.

Regards,
Werner

> -----Ursprüngliche Nachricht-----
> Von: ext Alejandro Cabrera Obed [mailto:acabrera at sintys.gov.ar] 
> Gesendet: Mittwoch, 6. August 2008 20:12
> An: Dittmann, Werner (NSN - DE/Munich)
> Cc: voi >> "VOIPSEC (list)"
> Betreff: Re: ZRTP and Asterisk
> 
> Thanks Werner,
> 
> I used Wireshark in order to trace ZRTP packets, but I don't remember
> what I see. I'll do it again.
> 
> Phill Zimmerman told me to use tha ZRTP patch in Asterisk, and he was
> surprised when I tell my experience among Twinkle+libzrtp.
> 
> Just one more question: which scenario do you use Twinkle+ZRTP in ???
> Maybe direct connections or through a SIP server like Openser ???
> 
> Thanks a lot !!!
> 
> Alejandro
> 
> Dittmann, Werner (NSN - DE/Munich) wrote:
> >
> > Hello Alejandro,
> >
> > just got a link to your question on the VOIPSEC list
> > regarding this topic. I'm quite familiar with the
> > GNU ZRTP / Twinkle implementation of ZRTP, however
> > I'm not familiar with Asterisk.
> >
> > Here just some ideas why it could work with Twinkle:
> >
> > Twinkle is quite flexible with respect to audio codecs,
> > it supports a lot of them.
> >
> > Now, if the Twinkle clients agree on a codec and Asterisk
> > does not need to re-encode the RTP packets and just transport
> > them unaltered between the clients then ZRTP will obviously work.
> >
> > Depending on the Twinkle and Zfone versions a connection between
> > Twinke and Zfone is possible or not  :-) - computers are digital
> > devices ;-) .
> >
> > (Just checked the Twinkle Web site: Michel de Boer did not
> > yet update to the latest version of ZRTP. I use a newer/modified
> > version here in my sandbox.)
> >
> > To analyse this further I would need a protocol trace (Wireshark)
> > to analyse the traffic. My first guess: something is wrong
> > with the Asterisk configuration and twinkele is able (somehow)
> > to perform direkt client-to-client connections.
> >
> >
> > Best regards,
> > Werner
> >
> 
> 
> -- 
> Ing. Alejandro Cabrera Obed
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