I still do not support adoption. To first- and second- order approximation,
these should never be used for the per-connection TLS signature in the
CertificateVerify message, and risks being an attractive nuisance.
The claim that folks want this for X.509 signatures is slightly more
plausible to me, but that's not a reason to add it to the TLS signature.
While X.509 signatures do technically peek into TLS codepoints (even if in
practice it's never really worked terribly well), the WG already has
precedent for squaring this exact circle:
RSASSA-PKCS1-v1_5 algorithms: Indicates a signature algorithm using
RSASSA-PKCS1-v1_5 [RFC8017] with the corresponding hash algorithm
as defined in [SHS]. These values refer solely to signatures
which appear in certificates (see Section 4.4.2.2) and are not
defined for use in signed TLS handshake messages, although they
MAY appear in "signature_algorithms" and
"signature_algorithms_cert" for backward compatibility with
TLS 1.2.
David
On Mon, Jul 14, 2025 at 6:06 PM Sean Turner <[email protected]> wrote:
> We kicked off an adoption call for Use of SLH-DSA in TLS 1.3; see [0]. We
> called consensus [1], and that decision was appealed. We have reviewed the
> messages and agree that we need to redo the adoption call to get more input.
>
> What appears to be the most common concern, which we will take from Panos'
> email, is that "SLH-DSA sigs are too large and slow for general use in TLS
> 1.3 applications". One way to address this concern is to add an
> applicablity statement to address this point. We would like to propose that
> this (or something close to this) be added to the I-D:
>
> Applications that use SLH-DSA need to be aware that the signatures sizes
> are large; the signature sizes for the cipher suites specified herein range
> from 7,856 to 49,856 bytes. Likewise, the cipher suites are considered
> slow. While these costs might be amoritized over the cost of a long lived
> connection, the cipher suites specified herein are not considered for
> general use in TLS 1.3.
>
> With this addition in mind, we would like to start another WG adoption
> call for draft-reddy-tls-slhdsa. If you support adoption with the above
> text (or something similar) and are willing to review and contribute text,
> please send a message to the list. If you do not support adoption of this
> draft with the above text (or something similar), please send a message to
> the list and indicate why. This call will close at 2359 UTC on 28 July 2025.
>
> Cheers,
> Deirdre, Joe, and Sean
>
> [0] https://mailarchive.ietf.org/arch/msg/tls/o4KnXjI-OpuHPcB33e8e78rACb0/
> [1] https://mailarchive.ietf.org/arch/msg/tls/hhLtBBctK5em6l82m7rgM6_hefo/
> [2] https://datatracker.ietf.org/doc/draft-reddy-tls-slhdsa/
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