> Why not do both at the same time? I understand that a TLSA record in and of its own would suffice technically, but combined with the regular CA-based PKI, I figured the robustness would increase.
That seems quite complicated while not increasing security by much, or at all?
I don't necessarily see the complication. The benefit would be that I, the domain owner, would be able to communicate to clients what certificate they should be expecting, and in turn, clients would be able to tell if there's a mismatch. Sounds like a simple win to me.
According to my understanding, multiple CAs can issue a certificate covering the same domain just fine, so that on its own showing up on the CT logs is not a sign of CA compromise, just a clue. Could then check CAA, but that is optional and clients are never supposed to check that according to the standard, only the CAs (which again the idea is that one or more are compromised in this scenario). So there's a gap there. This gap to my knowledge is currently bridged by people auditing CT manually, and is the gap that would be filled with DANE in this setup in my thinking, automating it away (or just straight up providing it, because I can imagine that a lot of domain owners do not monitor CT for their domains whatsoever).
That seems quite complicated while not increasing security by much, or at all?