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[CFRG] Re: Silithium - A Compact, Efficient and Non-separable Hybrid Signature

Ilari Liusvaara <ilariliusvaara@welho.com> Thu, 16 July 2026 07:10 UTC

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Date: Thu, 16 Jul 2026 10:10:02 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
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Subject: [CFRG] Re: Silithium - A Compact, Efficient and Non-separable Hybrid Signature
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On Thu, Jul 16, 2026 at 06:26:19AM +0000, John Mattsson wrote:
> One difference is that Mothma-Ed25519-ML-DSA-65 requires retaining
> SHA-2, whereas Silithium (which I assume can be used with
> edwards25519) can be implemented using only SHA-3. If people plan
> to use hybrids long-term, that is an advantage for Silithium.

Another advantage for long-term use is resistance to zombie crypto.


> The first discussion I am aware of that Q o P preserves the SUF-CMA
> property of Q is:
> https://mailarchive.ietf.org/arch/msg/pqc/She2XoyCWl9paHP8GvLUdciRGYE/

An issue with that kind of one-sided SUF-CMA is that with protocols
needing SUF security, the classical component does not add security,
as either the PQ part holds, or there is a serious security problem.

For using hybrids with protocols needing SUF, one needs two-sided
SUF-CMA. Which can not be archived in black-box model.




-Ilari

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