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by moxie
4987 days ago
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I conceptualize Convergence as providing trust agility for situations where a client needs third party verification. TACK is about reducing the number of situations where we even need to trust a third party at all. The latter helps the former by making it easier to deploy. If TACK were the norm, then the only purpose CAs would serve is to introduce clients to websites they have never seen before (rather than authenticating every single connection to a website during every page load to that website). By taking a bite out of the problem, we feel the remainder will be easier to solve. And yeah, hopefully we can position convergence as that solution. It's also easier to get TACK done with browser vendors, simply because it's well encapsulated as a TLS extension, is fairly uncontroversial, and requires them to write less code. Basically, we feel it's a good first step. |
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However what happens if the MITM attack is on the other end, in other words somebody has got into a hosting providers network and is MITMing a bunch of traffic to some of their servers.
They could use this to pass back bullshit certs/public keys to all clients (including notaries) who connect to servers they have MITMd.
One way to prevent this of course would be to have the server keep it's own list of notaries and self-check every so often and alert clients if something appears wrong.
However here you are relying on server administrators keeping this configured and working. I could imagine less scrupulous administrators on strict SLAs disabling this and letting it fail in a way that is silent to the end user to avoid downtime. This would be more difficult to do with the traditional CA structure since the attacker would need a valid cert for the site or would need to SSL strip everything (which would eventually get noticed).
Or do I have this wrong and it is intended to augment the existing CA structure rather than replace it?