How to distrust a CA without any certificate errors

Re:How to distrust a CA without any certificate errors by Spivak on Friday March 07, 2025 @11:43AM (#43291667)

Web PKI is not TOFU in the specific instance where you have an a priori trusted url you know about. But I, and others, argue that this isn't actually that strong of a guarantee in practice. I'm just trusting that this URL is the real life entity I think it is. The only thing you get is that you're connected to someone who has control of the domain. And it's pretty clear that with ACME and DNS challenges we don't need a huge centralized system to do this much weaker thing, you just need any DNS server you trust, it can even be yours.

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Re:How to distrust a CA without any certificate errors by lxgr on Friday March 07, 2025 @11:51AM (#43291747)

> The only thing you get is that you're connected to someone who has control of the domain.

Yes, that's the entire scope of the web PKI, and with the exception of EV certificates it never was anything else.

> it's pretty clear that with ACME and DNS challenges we don't need a huge centralized system to do this much weaker thing

Agreed – what we are doing today is primarily a result of the historical evolution of the system.

"Why don't we just trust the DNS/domain registry system outright if we effectively defer most trust decisions to it anyway" is a valid question to ask, with some good counterpoints (one being that the PKI + CT make every single compromise globally visible, while DANE does not, at least not without further extensions).

My objection is purely on terminology: Neither the current web PKI nor any hypothetical DANE-based future would be TOFU. Both delegate trust to some more or less centralized entity.

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