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

[Sophie Schmieg <[e-mail]>]

My main criticism of hybrid signatures is and remains that there is no
clear alternative that has enough political capital behind it to make it
worthwhile to bet on, especially while pure constructions continue to make
progress. Having even more hybrid constructions beyond the original LAMPS
RFC feels counterproductive when it comes to that. If proponents of hybrid
signatures could chose just one combination and construction, it would be
far easier to implement and throw support behind. With KEMs, this is what
happened with X-Wing (and the TLS hybrid), but so far with signatures,
every time I look there is yet another incompatible construction that yet
another even smaller splinter group would like to see supported.

On Thu, Jul 16, 2026 at 6:54 AM Ilari Liusvaara <[e-mail]>
wrote:

> On Thu, Jul 16, 2026 at 08:16:48AM +0000, John Mattsson wrote:
> > On 2026-07-16, 08:57, "Simon Josefsson" <simon=
> [e-mail]> wrote:
> >
> > >I believe the point of using hybrids is to continue using old crypto as
> > >a black-box in parallel with new crypto, in a safe way. A hybrid that
> > >doesn't re-use traditional crypto as a black box seems esoteric to me.
> >
> > There seem to be different opinions about the purpose of hybrids. The
> > more obsolete cryptographic components PQ/T hybrids rely on, the more
> > important it is to enable a migration path for removing those
> > components once they become pure overhead and no longer provide
> > meaningful security. In my view that will happen sometime around 2035.
>
> I think hybrids are about relying on multiple cryptographic assumptions
> as alternatives to each other. Hybrids can be inseparable into black-box
> components, and there exists problems that are inherently inseparable
> (not admitting a black-box solution, even if overall solution exists or
> is even known).
>
> There are costs and benefits for breaking a black box. All the former
> contets of the black box become complexity. But the black box itself is
> no longer around to cause problems.
>
>
>
>
> -Ilari
>
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-- 

Sophie Schmieg | Information Security Engineer | ISE Crypto |
[e-mail]