[tptacek]

Adam Langley explains in "Why Not DANE In Browsers" that this is not in fact the case, and that DANE will ultimately just expand the number of trust anchors; you can't even get things narrowed down to just the governments controlling your records.

Further: a mis-issuing CA can be put to death (as happened to the largest CA when Google caught them mis-issuing). You can't revoke a TLD.

Meanwhile, CT actually exists today and is meaningfully combating misissuance, and obviously does not rely on DNSSEC to function.

[Ajedi32]

> Adam Langley explains in "Why Not DANE In Browsers" that this is not in fact the case, and that DANE will ultimately just expand the number of trust anchors

This is false. That article makes no such claims.

[tptacek]

There are two ways that you might wish to use DANE in a web browser: either to block a certificate that would normally be considered valid, or to bless a certificate that would normally be rejected. The first, obviously, requires that DANE information always be obtained—if a lookup failure was ignored, a network attacker with a bad certificate would just simulate a lookup failure. But requiring that browsers always obtain DANE information (or a proof of absence) is nearly implausible

[Ajedi32]

That paragraph does not claim DANE expands the number of trust anchors.

As magila stated, registrars are already a trust anchor for domain validated certificates. Trusting a certificate directly via DANE vs through a domain-validated certificate doesn't change that. It does, however, cut CAs out of the process, which reduces the number of trust anchors.

[tptacek]

If you can't use DANE to block certificates that the WebPKI says are valid, then you're stuck trusting both DANE and the CAs. Browsers don't trust DANE today. Ergo, adoption of DANE would expand the number of trust anchors.

[Ajedi32]

Assuming we need to keep backwards compatibility indefinitely that's true, but that still wouldn't expand the number of trust anchors. DANE isn't a new trust anchor, it's just a more direct way of trusting preexisting trust anchors (DNS registrars). Even if you don't use or support DANE you still need to trust the registrars.

[tptacek]

No, that is false. DNS registrars do not sign CA certificates and, without DANE, are not trust anchors in the WebPKI. And, of course, with DANE, they would essentially gain that status. This is a plain fact, but you can reason your way to it axiomatically by (again) considering how trust would be rescinded: Google singlehandedly killed the web's largest CA after a misissuance, but obviously cannot do that to .COM in a DANE world.

When your argument starts depending on redefinitions of well-established concepts, that's a sign that you should reconsider it.

[magila]

I was speaking more in a hypothetical sense, but you're right. The DNS as currently implemented is sufficiently broken so as to preclude securing it.