[pyre]

The real problem with revocation lists for websites is that there is no secure channel to transfer them over. You can't transfer them over SSL because you don't know which certs you shouldn't trust until you get the list.

If someone is alreay man-in-the-middling you with a cert you trust, they can easily filter the revocation lists that you download.

[chalst]

But you can know whether a CRL is valid, provided Apple's own CA hasn't been compromised. If Apple were to issue a complete CRL every 6 hours or so, then man-in-the-middle filtering won't work since clients can simply not trust any new signatures until they have seen the current CRL.

So the man-in-the-middle attack can keep the client ignorant of the contents of the CRL, but can't trick the client into believing a revoked certificate has not been revoked.

SSL is a red herring here, since we care about authenticity, not privacy.

[pyre]

Also...

  > provided Apple's own CA hasn't been compromised

We've been seeing this happen a lot lately, so that's a big assumption.

[pyre]

I was mostly commenting on the first paragraph in relation to the web, not specifically about Apple using certificates.