Hi all,

I am mostly ambivalent, but slightly leaning positive about SLH-DSAs future in 
TLS. My thoughts on SLH-DSA in TLS are the following:

Against:
- By almost every metric that I have measured TLS handshake performance, 
SLH-DSA (SPHINCS+) performance is abysmal (handshake size, latency)
- The potentially much more relevant parameters with reduced numbers of 
signatures have not been selected by NIST yet, but are supposed to be upcoming.

Pro:
- Public keys are tiny, this could be beneficial for devices with limited 
storage (e.g. as secondary algorithm)
- Implementing SLH-DSA, simplified, is essentially slapping a loop on a hash 
function. This makes its code size very manageable, especially if there is 
already a (good) hash implementation on a device (as one would likely already 
ship as part of ML-KEM or ML-DSA).
- Some applications might not care about the latency (suggested 3GPP)

A secondary question is whether an RFC is necessary, for which I think the same 
reasoning applies as with ML-DSA.

It would be very helpful if more potential users come forward.

Cheers,

Thom

> Op 16 mei 2025, om 23:20 heeft David Benjamin <[email protected]> het 
> volgende geschreven:
> 
> I share the confusion about what this is for. SLH-DSA is handy, but it seems 
> to not fit TLS very well at all.
> 
> There's also rather a lot of algorithms proposed to be added here, so I am 
> correspondingly that many missing use cases worth of confused. 
> 
> On Fri, May 16, 2025, 17:06 Watson Ladd <[email protected] 
> <mailto:[email protected]>> wrote:
>> I don't support adoption.
>> 
>> It is not clear to me what an RFC for a ciphersuite is supposed to
>> signal. To the extent it indicates this solution is prefered, the fact
>> that SLH-DSA is a very awkward fit for server auth makes me think we
>> should say no.
>> 
>> Sincerely,
>> Watson Ladd
>> 
>> On Fri, May 16, 2025 at 6:28 AM Sean Turner <[email protected] 
>> <mailto:[email protected]>> wrote:
>> >
>> > We are continuing with our WG adoption calls for the following I-D: Use of 
>> > SLH-DSA  in TLS 1.3 [1]; see [2] for more information about this tranche 
>> > of adoption calls. If you support adoption and are willing to review and 
>> > contribute text, please send a message to the list. If you do not support 
>> > adoption of this draft, please send a message to the list and indicate 
>> > why. This call will close at 2359 UTC on 30 May 2025.
>> >
>> > Reminder:  This call for adoption has nothing to do with picking the 
>> > mandatory-to-implement cipher suites in TLS.
>> >
>> > Cheers,
>> > Joe and Sean
>> >
>> > [1] https://datatracker.ietf.org/doc/draft-reddy-tls-slhdsa/
>> > [2] https://mailarchive.ietf.org/arch/msg/tls/KMOTm_lE5OIAKG8_chDlRKuav7c/
>> > _______________________________________________
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>> > <mailto:[email protected]>
>> 
>> 
>> 
>> -- 
>> Astra mortemque praestare gradatim
>> 
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