Hehehe. Well, I would agree that composites are preferable to this model.
But I also think not doing hybrids is preferable to both. :-)

On Wed, Apr 29, 2026, 20:44 Andrei Popov <[email protected]> wrote:

> Indeed. A good argument in favor of composites, even if David did not
> intend it this way 😊
>
>
>
> Cheers,
>
>
>
> Andrei
>
>
>
> *From:* David Benjamin <[email protected]>
> *Sent:* Wednesday, April 29, 2026 4:56 PM
> *To:* ekr <[email protected]>
> *Cc:* [email protected]
> *Subject:* [EXTERNAL] [TLS] Re: anyone interested in multiple
> CertificateVerify messages?
>
>
>
> The main challenge with doing something like that is not in TLS, but in
> what leaks out of TLS. Systems everywhere are designed around a notion of
> "the" peer certificate that you received over the connection. There's the
> tls-server-end-point channel binding, but more broadly, TLS APIs tend to
> expose a "get peer certificate" function.
>
>
>
> I think this thus falls under the "way too complicated and expensive to
> justify doing" bucket. Once you have to move mountains to get the hybrid
> property, it becomes extremely not worth it.
>
>
>
> On Wed, Apr 29, 2026 at 7:37 PM Eric Rescorla <[email protected]> wrote:
>
> Even stipulating for the moment that it's good to sign with multiple
> certificates, I do not believe that this is the correct approach to doing
> so.
>
>
>
> If we're going to do something here, something more like
> https://datatracker.ietf.org/doc/draft-yusef-tls-pqt-dual-certs/ seems
> like a better starting point.
>
>
>
> -Ekr
>
>
>
>
>
> On Wed, Apr 29, 2026 at 4:27 PM Stephen Farrell <[email protected]>
> wrote:
>
>
> Hiya,
>
> Given that it may be the case that getting certificates for
> composite signing keys could be impractical and also involve
> a combinatoric explosion in the number of credentials severs
> would need to have available, I wonder if anyone has explored
> whether it'd be useful to look at defining a way in which a
> server (or, I guess, a client) could authenticate using more
> than one CertificateVerify message?
>
> I guess that figuring that all out, and getting it implemented
> and deployed would involve a pile of work, but ISTM it might
> be useful, hence the question:-)
>
> Cheers,
> S.
>
> PS: If this isn't a bonkers idea, I'd be willing to do work on
> it, for whatever that'd be worth:-)
>
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