[chair hat off]

Ilari said:
> > I think if public key client ask is something that can signe things we
could
>> just ask client to sign a jws with key in question:

> That is not cryptographically kosher, and does not work with algorithms
that are not in JWS.

Currently, in order to get a cert you have to sign an ASN.1 CSR, regardless
of what protocol you will eventually use that key / certificate for. So (I
conjecture?) signing a JSON-based challenge instead of a CSR is not
substantially different from a cross-protocol security perspective.
That said, trying to define ACME PoP Challenges to match the protocol the
certificate is for will mean an explosion of new ACME Challenges -- TLS,
JWS, CWS, CMS, IKEv2, WiFi, etc etc etc -- and that sounds like an
operational nightmare that will almost certainly became a security issue
when people get it wrong. So I strongly vote that if we replace CSR with an
in-band ACME PoP challenge, that we just do it once and not try to match
the target protocol.

On Tue, 10 Mar 2026 at 06:52, Ilari Liusvaara <[email protected]>
wrote:

> On Tue, Mar 10, 2026 at 05:57:23PM +0900, Seo Suchan wrote:
> > I think if public key client ask is something that can signe things we
> could
> > just ask client to sign a jws with key in question:
>
> That is not cryptographically kosher, and does not work with
> algorithms that are not in JWS.
>
>
> > we need something else for kemtls though, because they can't sign
> > anything but makeing new random shared session key
>
> Have server send challenge ciphertext, and then have client
> decapsulate it and send MAC using the key.
>
> KEMTLS is not happening any time soon anyway.
>
>
>
>
> -Ilari
>
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