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Re: [Full-disclosure] FD / lists.grok.org - bad SSL cert

From: Tim <tim-security_at_nospam>
Date: Mon Jan 05 2009 - 23:35:14 GMT
To: Volker Tanger <vtlists@wyae.de>


> And as browsers usually do not check CRLs, there is no way preventing
> the use of wrongfully signed certificates short of distributing a
> "software update" (as was with the MS case). If browsers had a cert
> cache and checked it similar to SSH, MitM-attacks would be much harder.

Well, now you're just pushing the problem off on users. How many of them would check the certificate the first time? Does it matter to an end-user if their credit card info is stolen *only the first time* and not after that?

Certainly SSL's PKI has major problems. Many of these problems can be remedied through simple client software changes. Why is every CA treated the same? Why don't we start assigning levels of trust to different CAs? A web-of-trust would be a great way to go, so long as there's a way to hide it from end users. Who would be allowed to participate in the web of trust? Tough questions.

As a basic first step, perhaps what browsers need to start doing is to take all of those CAs out of the default install and replace it with just one. Their own. Sign all current CAs as sub-CAs. Turn on CRL checks by default to their servers and start tracking all revocations in one place. Then, when a CA starts misbehaving, deal with it through the central CRL or through a trust rating system which is separate from the standard certificate formats. Yeah, sure, it centralizes things in a bad way, but centralized CRLs are still better than none. Once the system is solidified, standardize and redistribute.

Some crazy ideas, I know. Feel free to shred them.

tim



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