3 ms·

You raise some good points. There are definitely some benefits to having a diversity of different trust anchors rather than just one. The problem though is that

You raise some good points. There are definitely some benefits to having a diversity of different trust anchors rather than just one. The problem though is that the way things are currently set up that diversity is somewhat of an illusion; DNS is still a central point of failure for all CAs (e.g. via the ACME DNS challenge), and each individual CA is also a single point of failure unto itself (a CA can issue certs for any domain, not just those of its customers). I also think you may be underestimating the amount of leverage browser developers have over DNS, should they choose to exercise it. If Google, Apple, Microsoft, and Mozilla all agreed tomorrow that they wanted to migrate the web to a new set of DNS root servers they could probably do it. (Though yes, it would be a huge ordeal for everyone involved.) The real reason we haven't gotten DANE transparency (or anything similar) is simply because it hasn't been a priority for browsers. (Why pressure DNS roots to improve a system that you aren't even using in the first place?) Still, I can't deny what you're saying. The CA system is probably a lot more flexible than a naively designed DNS-based system would be. I'll have to think about that a bit more. Maybe it would make sense to have something like SCTs in the certificate transparency system, where a number of different independently operated organizations all have to sign off on the validity of each cert _in addition_ to the DNS operator that actually issued the certificate. That way you'd get the benefits of diversified trust anchors without the downside of having hundreds of distributed single points of failure.

tptacek 4y ago
The browsers absolutely cannot migrate to a different set of DNS roots. It's only been in the last 5-10 years that they've managed to get as much control over the root programs as they have now, and there was a lot of behind-the-scenes drama involved in that. And TLS certificates are, when you come right down to it, a browser feature.
- Ajedi32 4y ago
  That was just a hypothetical example to illustrate how much power browser vendors have over the web; they wouldn't need to literally migrate to a different DNS root in order to effect change in this space, but I maintain they absolutely could go that far (again, hypothetically) if they all agreed and there were a sufficiently compelling reason. Browsers always had full control over CA root programs, it's just a question of how willing they were to actually assert themselves in that fashion. I agree they've become more bold about that over the years, but what Mozilla just did to TrustCo was always an option for the major browser vendors, both legally and technically (or at least since automatic updates became a thing). DNS is also effectively a browser feature these days, as evidenced by all the browsers suddenly supporting things like DNS-over-HTTPS despite host operating systems lacking support. Given a sufficiently smooth transition path for users and website operators, browser vendors could collectively decide to alter their DNS implementations in pretty much any way they want.
  - tptacek 4y ago
    I don't think this is really true at all, and I think it underestimates (significantly) the amount of behind-the-scenes work that went into the current WebPKI situation with activist root programs. I don't think there's any reason at all to believe that browsers would have similar success governing a DNS PKI, and there are specific reasons --- evidence, even --- to believe they wouldn't. We can go round and round on this stuff, but I feel like I'm repeating myself at this point.
    - Ajedi32 4y ago
      Like I said, I agree with you that a naive, purely DNS-based PKI would be less flexible in that regard. That was a good point, and well noted. However, the current status quo is sort of ignoring the big DNS-shaped elephant in the room. You can build all the validation and transparency solutions you want on top of the CA system, but it's still fundamentally dependent on the security of a DNS system that currently requires no cryptographic assurances that the records the CAs are validating against are actually correct.
ciupicri 4y ago
> If Google, Apple, Microsoft, and Mozilla all agreed tomorrow that they wanted to migrate the web to a new set of DNS root servers they could probably do it. They're already pushing DNS over HTTP.

tptacek 4y ago

The browsers absolutely cannot migrate to a different set of DNS roots. It's only been in the last 5-10 years that they've managed to get as much control over the root programs as they have now, and there was a lot of behind-the-scenes drama involved in that. And TLS certificates are, when you come right down to it, a browser feature.

Ajedi32 4y ago
That was just a hypothetical example to illustrate how much power browser vendors have over the web; they wouldn't need to literally migrate to a different DNS root in order to effect change in this space, but I maintain they absolutely could go that far (again, hypothetically) if they all agreed and there were a sufficiently compelling reason. Browsers always had full control over CA root programs, it's just a question of how willing they were to actually assert themselves in that fashion. I agree they've become more bold about that over the years, but what Mozilla just did to TrustCo was always an option for the major browser vendors, both legally and technically (or at least since automatic updates became a thing). DNS is also effectively a browser feature these days, as evidenced by all the browsers suddenly supporting things like DNS-over-HTTPS despite host operating systems lacking support. Given a sufficiently smooth transition path for users and website operators, browser vendors could collectively decide to alter their DNS implementations in pretty much any way they want.
- tptacek 4y ago
  I don't think this is really true at all, and I think it underestimates (significantly) the amount of behind-the-scenes work that went into the current WebPKI situation with activist root programs. I don't think there's any reason at all to believe that browsers would have similar success governing a DNS PKI, and there are specific reasons --- evidence, even --- to believe they wouldn't. We can go round and round on this stuff, but I feel like I'm repeating myself at this point.
  - Ajedi32 4y ago
    Like I said, I agree with you that a naive, purely DNS-based PKI would be less flexible in that regard. That was a good point, and well noted. However, the current status quo is sort of ignoring the big DNS-shaped elephant in the room. You can build all the validation and transparency solutions you want on top of the CA system, but it's still fundamentally dependent on the security of a DNS system that currently requires no cryptographic assurances that the records the CAs are validating against are actually correct.

ciupicri 4y ago

> If Google, Apple, Microsoft, and Mozilla all agreed tomorrow that they wanted to migrate the web to a new set of DNS root servers they could probably do it. They're already pushing DNS over HTTP.