Re: Module signing and post-quantum crypto public key algorithms

[Stephan Mueller <smueller@chronox.de>]

Am Freitag, 7. November 2025, 11:03:49 Mitteleuropäische Normalzeit schrieb 
David Howells:

Hi David,

> Stefan Berger <stefanb@linux.ibm.com> wrote:
> > On 6/16/25 1:27 PM, Simo Sorce wrote:
> > > Of course we can decide to hedge *all bets* and move to a composed
> > > signature (both a classic and a PQ one), in which case I would suggest
> > > looking into signatures that use ML-DSA-87 + Ed448 or ML-DSA-87 + P-521
> > > ,ideally disjoint, with a kernel policy that can decide which (or both)
> > > needs to be valid/checked so that the policy can be changed quickly via
> > > configuration if any of the signature is broken.
> > 
> > FYI: based on this implementation of ML-DSA-44/65/87
> > 
> > https://github.com/IBM/mlca/tree/main/qsc/crystals
> 
> The problem with that is that the Apache-2 licence is incompatible with
> GPLv2. Now, it might be possible to persuade IBM to dual-license their
> code.

The code used as a basis for the current approach (leancrypto.org) offers 
hybrids with ED25519 and ED448) including the X.509/PKCS7 support.

However, please note that the X.509 specification for storing hybrid public 
keys is not yet completed and there is still some work on the draft IETF 
standard [1].

Side note: the leancrypto code base uses the Linux kernel X.509/PKCS7 parser 
code where the relevant handler functions (see [2]) could be relatively 
quickly transplanted into the kernel if needed.

[1] https://lamps-wg.github.io/draft-composite-sigs/draft-ietf-lamps-pq-composite-sigs.html

[2] https://github.com/smuellerDD/leancrypto/blob/master/asn1/src/
x509_cert_parser.c

Ciao
Stephan