On 30/04/2024 16:13, Brendan McMillion wrote:

    Of course this is possible in theory, there are no standards
    police, but this argument overlooks the gargantuan technical and
    economic costs of deploying this kind of private extension. You'd
    need to convince a diverse population of implementers on both the
    client and server side to adopt and enable your thing.


I don't believe my hypothetical private extension would need to be adopted by any servers, just clients. And due to power laws, adoption by one or two clients would provide visibility into a substantial section of Internet traffic.
This is just an observation that unilateral actions taken by major players can screw things up for many people. It's true, but it has little bearing on what we're weighing up here.

    Can you expand on how this draft enables the more rapid distrust
    of failed CAs?


 This is described in more detail in section 9.1 of the draft. Currently we have the problem that, as long as any older RP relies on a given root, subscribers have to keep using it, which means newer RPs have to keep trusting it.

This doesn't apply in case we're distrusting a CA because it's failed. In 9.1 we're rotating keys. As I laid out in my initial mail, we can already sign the new root with the old root to enable rotation. There's no size impact to up-to-date clients using intermediate suppression or abridged certs.


    I'm confused by this remark. Are there clients which would
    tolerate a certificate if only it had a longer lifetime? Is there
    any circumstance in which you would have both a long-life and
    short-life certificate available, and you would prefer to serve
    the long-life cert?


 Yes, especially when you push to shorter and shorter lifetimes (say, 1 day, 1 hour), you start to have the issue that not all clients will have sufficiently accurate clocks to verify them. Clients with accurate clocks can advertise support for a root that issues short-lived certs while clients that don't will not advertise support for this root, and with TE we can support both.

Firefox already supports Delegated Credentials for exactly this use case and which addresses clock skew, but DCs have never seen much use as far as I know. In any case, this is an already solved problem.
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