On Thu, Jan 23, 2014 at 11:52 AM, carlo von lynX < [email protected]> 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. -- Tony Arcieri
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