[openpgp] Re: Size of ML-DSA Secret key in draft-ietf-openpg p-pqc and other considerations

Hi Aron,

On Mon, 2025-02-10 at 17:14 +0000, Aron Wussler wrote:

> Note that the specification is only for the wire format, and transferring among identical tokens will still be possible, no matter the format we choose.

It think this might come to bite in the future, but I do not have the
energy to argue for it now. Once we'll have interop issue I'll let you
guys deal with it :)

> 2. Code points
> This was discussed at IETF 117, 118 and 119. We concluded that this could be done in a separate doc, adding a further codepoint for ML-DSA (or ML-KEM) as standalone when the WG feels ready for it.

Just to be clear the reason I am asking is that CNSA 2.0 "seems" to
exclude hybrids (I know, not my choice, they also do not allow SLH-DSA
which I would very much prefer for long term signatures... ).

I think I can "work around" this by simply ignoring the spec and
considering a signature valid even if the EdDSA part is unchecked, and
live with that.

For tokens that support only one key this is more challenging, but I
guess one of the two keys will have to stay on disk and be less secure
until a new spec that allows for "pure" algorithms is provided.

> 3. Signature data digests
> I honestly have seen that requirement, and am still wondering why the hell it is there. I don't understand it, and the "SHA-3 limits interoperability" reason sounds really weird to me, feels to me as "we have a machine in the basement that can break this hash". Happy to hear other reasons tho.
> 
> Said this, if for you this is a blocker for RHEL, I think we can revisit the hash binding requirement.

Yes this is the only "blocker" I have,
We use PGP for signing packages and we really need a way to be CNSA 2.0
compliant.
At this time it means ML-DSA-87 for signatures and either SHA-384 or
SHA-512 for content hashes.

I do not think the NSA can break SHA2 as they allow SHA3/SHAKE as
internal implementations in the signature algorithms. I think this is
more of a case of: "we have accelerators that can speed up SHA2 but not
SHA3 and we want to keep using them for the time being to produce
content hashes"

This is my speculation, several of their positions are questionable,
but I still need to be able to support their preferences as they are
not broken (as far as we know).

Best,
Simo.

-- 
Simo Sorce
Distinguished Engineer
RHEL Crypto Team
Red Hat, Inc

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