[liberationtech] WebRTC - The next big surveillance machine

[Patrick Schleizer]

Tony Arcieri:
> On Thu, Jan 23, 2014 at 11:52 AM, carlo von lynX <
> lynX at time.to.get.psyced.org> wrote:
> 
>>> say it not secure. WebRTC is compatible with ZRTP key-authentication
>> which
>>> builds in a video-based auth scheme and should stop MITM attacks (last
>> time
>>
>> You can't diffie-hellman yourself out of a MITM. If the fundamental link
>> is unsafe, you can make all the ephemeral keys you like - the observer can
>> trace them all.
>>
> 
> You should take a look at how ZRTP actually works, particularly Matt
> Green's analysis:
> 
> http://blog.cryptographyengineering.com/2012/11/lets-talk-about-zrtp.html
> 
> ZRTP authentication works by negotiating what's called a "short
> authentication string" between peers. If there's no MitM, both sides will
> see the same string.
> 
> To authenticate, you start a voice/video call. You will see the person
> you're expecting, but at this point the link is insecure and may be MitMed.
> 
> However, Alice can read off the Short Authentication String to Bob. Short
> of fancy realtime video editing and voice impersonators, the string will be
> incorrect if the connection is being MitMed.
> 
> Once this has been done successfully once, ZRTP stores some "continuity
> data" so the next time you authenticate to the same person, the previous
> authentication will ensure future connections are secured.

The latter, the "continuity data" is implementation specific.

I wonder how my voip clients actually support this.

Last time I asked the PhonerLite developer, he told me, that PhonerLite
does not support it.