I agree with John. I will give a concrete example to help clarify the
uncertainty. DTLS based security solution for SCTP has been mandated by
3GPP for several key interfaces. These interfaces involve long-lived DTLS
sessions. For more details, see the liaison statement from 3GPP:
https://datatracker.ietf.org/liaison/1851/. The DTLS-in-SCTP standrds work
is done in the TSVWG WG.

-Tiru

On Tue, 22 Jul 2025 at 12:20, John Mattsson <john.mattsson=
40ericsson....@dmarc.ietf.org> wrote:

> I feel like I need re-iterate that according to 3GPP specifications, SLH-DSA
> is already allowed (MAY/OPTIONAL) to support and use for all uses of TLS
> in 3GPP deployments and that vendors are planning to support both ML-DSA
> and SLH-DSA. As Matt correctly points out it is not yet decided which PQC
> signature algorithms 3GPP specifications will have as SHOULD/MUST support.
>
> Cheers,
>
> John
>
>
>
> *From: *Matt G1 <Matt.g1=40ncsc.gov...@dmarc.ietf.org>
> *Date: *Tuesday, 22 July 2025 at 11:29
> *To: *Loganaden Velvindron <logana...@gmail.com>, Simon Josefsson <simon=
> 40josefsson....@dmarc.ietf.org>
> *Cc: *TLS List <tls@ietf.org>
> *Subject: *[TLS] Re: Second WG Adoption Call for Use of SLH-DSA in TLS 1.3
>
> [You don't often get email from matt.g1=40ncsc.gov...@dmarc.ietf.org.
> Learn why this is important at
> https://aka.ms/LearnAboutSenderIdentification ]
>
> I feel like I need re-iterate that use cases for SLH-DSA have not been
> addressed in 3GPP meetings. The discussion will happen over the next 6
> months. We may or may not come to consensus to wish to use it.
>
> Matt
>
> NCSC Telecoms Security Consultant
>
>
> -----Original Message-----
> From: Loganaden Velvindron <logana...@gmail.com>
> Sent: 21 July 2025 05:53
> To: Simon Josefsson <simon=40josefsson....@dmarc.ietf.org>
> Cc: TLS List <tls@ietf.org>
> Subject: [TLS] Re: Second WG Adoption Call for Use of SLH-DSA in TLS 1.3
>
> [You don't often get email from logana...@gmail.com. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification ]
>
> I also support adoption of the draft. If there is a use case for 3gpp, I'm
> ok with that.
>
> On Sat, 19 Jul 2025 at 22:49, Simon Josefsson <simon=
> 40josefsson....@dmarc.ietf.org> wrote:
> >
> > I support adoption of the draft, and believe SLH-DSA in TLS would be
> > useful and that a stable reference in the form of an RFC would be good.
> >
> > I think the people who have concerns with the performance assume the
> > intended use is for regular web browser HTTPS use, but TLS has broader
> > applicability than that.  50kb sizes is peanuts for the majority of
> > applications today, and you may compare with 1MB handshakes as for
> > Classic McEliece [1] which is still performant for many use-cases.
> > Performance on modern machines are negligible, slower than what RSA
> > was in SSL 30 years ago on then typical machines.  So I would disagree
> > with the notion that SLH-DSA is slow, and suggest that we let users
> > decide how to balance performance to (perceived) security.
> >
> > /Simon
> >
> > [1]
> >
> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww%2F&data=05%7C02%7Cjohn.mattsson%40ericsson.com%7Cc6e3804471cb437ac51f08ddc90243f7%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C638887733753195174%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=H8DztUNNzMNxaulvcyxeZR%2BDaEbu5WUI%2BZm4hjiNQ3M%3D&reserved=0
> .
> > wolfssl.com%2Fannouncing-mcwolf-classic-mceliece-support-with-wolfssl%
> > 2F&data=05%7C02%7Cmatt.g1%40ncsc.gov.uk%7C658ad8d442be497c63ae08ddc812
> > a2db%7C14aa5744ece1474ea2d734f46dda64a1%7C0%7C0%7C638886704564536777%7
> > CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlA
> > iOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Dpu3n
> > srM9sPaWFv4sQnnpibD8l19opMipusegEuI3wc%3D&reserved=0
> >
> > Sean Turner <s...@sn3rd.com> writes:
> >
> > > 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://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fma%2F&data=05%7C02%7Cjohn.mattsson%40ericsson.com%7Cc6e3804471cb437ac51f08ddc90243f7%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C638887733753238286%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=J0FeB4Xe%2B7zL0bwiL9q8cS24YSAx4zUecAMBnlmDP8c%3D&reserved=0
> > > ilarchive.ietf.org%2Farch%2Fmsg%2Ftls%2Fo4KnXjI-OpuHPcB33e8e78rACb0%
> > > 2F&data=05%7C02%7Cmatt.g1%40ncsc.gov.uk%7C658ad8d442be497c63ae08ddc8
> > > 12a2db%7C14aa5744ece1474ea2d734f46dda64a1%7C0%7C0%7C6388867045645618
> > > 08%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwM
> > > CIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sda
> > > ta=%2Bp6skyMbRIIBoCtVOq8S7lscwywomTgz18nze8bVsak%3D&reserved=0
> > > [1]
> > >
> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fma%2F&data=05%7C02%7Cjohn.mattsson%40ericsson.com%7Cc6e3804471cb437ac51f08ddc90243f7%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C638887733753267328%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=ADn9D72C6c7GvTuMrPI9ZjH3mWYNkFiPZxz%2BsMwq4HM%3D&reserved=0
> > > ilarchive.ietf.org%2Farch%2Fmsg%2Ftls%2FhhLtBBctK5em6l82m7rgM6_hefo%
> > > 2F&data=05%7C02%7Cmatt.g1%40ncsc.gov.uk%7C658ad8d442be497c63ae08ddc8
> > > 12a2db%7C14aa5744ece1474ea2d734f46dda64a1%7C0%7C0%7C6388867045645759
> > > 96%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwM
> > > CIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sda
> > > ta=SL6FFCWDmn%2BxnhzGuoJjdV0HqbkrDL%2Bx%2F8Ra99MQinI%3D&reserved=0
> > > [2]
> > >
> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fda%2F&data=05%7C02%7Cjohn.mattsson%40ericsson.com%7Cc6e3804471cb437ac51f08ddc90243f7%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C638887733753285746%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=YFrpnHjAiApfP%2BMfpbVTQlzkwepu011wTLNhoUHjLRA%3D&reserved=0
> > > tatracker.ietf.org%2Fdoc%2Fdraft-reddy-tls-slhdsa%2F&data=05%7C02%7C
> > > matt.g1%40ncsc.gov.uk%7C658ad8d442be497c63ae08ddc812a2db%7C14aa5744e
> > > ce1474ea2d734f46dda64a1%7C0%7C0%7C638886704564589656%7CUnknown%7CTWF
> > > pbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiI
> > > sIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=j3AEujdi2W7kFT6
> > > A6nD2JFPMHqskoPJ196TiKWErguk%3D&reserved=0
> > > _______________________________________________
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