slh-dsa: update to FIPS 205 final

[tarcieri]

It's out: https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.205.pdf

cc @tjade273

A.1 Changes From FIPS 205 Initial Public Draft

The differences from Version 3 of the SPHINCS+ specification described in Appendix A were
included in the draft version of this standard (FIPS 205 ipd) that was posted on August 24, 2023.
Based on comments that were submitted on FIPS 205 ipd, the SLH-DSA signature generation and
verification functions were modified to include domain separation cases in which the message
is signed directly and in which a digest of the message is signed. The changes were made by
modifying the inputs to the signing and verification functions (see Algorithms 22, 23, 24, and 25).

[DiscordJim]

Anyone currently working on this? Would be thrilled to help out.

Also: FIPS 204

[tarcieri]

@DiscordJim might wait a day to hear from @tjade273, otherwise go for it

[DiscordJim]

@tarcieri Sounds good. Ideally I'd like to work on the 204 implementation first. Do you guys have a Discord or something of the like?

[tarcieri]

@DiscordJim you can find some discussion about implementing ML-DSA in #8. There's currently an empty ml-dsa crate in-tree. Ideally it would share some code with ml-kem. You can chat about it on our Zulip

[tjade273]

Nice! I can take care of this tomorrow morning

[tarcieri]

Fixed in #844