[CFRG] Re: [lamps] Cross-testing update on LAMPS Composite and cfrg-concrete-hybrid-kems

[John Mattsson <[e-mail]>]

Hi Mike,

draft-ietf-lamps-pq-composite-kem-08 states:

”At the time of writing, [SP-800-227] is in its public draft period and not yet in force.”

I think the first check should be to check that draft-ietf-lamps-pq-composite-kem is compatible with the final version of SP 800-227 which is now “in force”. As stated in FIPS 203, SP 800-227 provides requirements for the use of ML-KEM in applications.

Cheers,
John

From: Mike Ounsworth <[e-mail]>
Date: Thursday, 16 October 2025 at 15:31
To: CFRG <[e-mail]>, [e-mail] <[e-mail]>, LAMPS WG <[e-mail]>
Subject: [lamps] Cross-testing update on LAMPS Composite and cfrg-concrete-hybrid-kems
Hi CFRG, HPKE, and LAMPS.

This is just a status update.


draft-ietf-lamps-pq-composite-kem has run out of time and we're gonna ask to start WGLC within a few days (the composite-sigs has passed WGLC yesterday).

One outstanding item was alignment with cfrg-concrete-hybrid-kems. I just pulled the latest test vectors from  https://github.com/cfrg/draft-irtf-cfrg-concrete-hybrid-kems , ran them through a script I wrote that bolts on to the lamps reference implementation to convert a cfrg-concrete-hybrid-kems test vector into a lamps-composite-kem test vector, and tests them. Results: we are cross-compatible on X-Wing, but not on P256 (and that's after hacking my script to use the CFRG label not the LAMPS label, so there's clearly some other bug at play, but I have no idea what, so of course I assume it's on the cfrg reference impl side 😋).

MLKEM768_X25519:
        ss from CFRG test vectors, and decapsulated ss
        60447f94b1e3675f09dbc4bc1abe8eafa14aed544547637aa980c3822ddd8578
        60447f94b1e3675f09dbc4bc1abe8eafa14aed544547637aa980c3822ddd8578

MLKEM768_P256:
        ss from CFRG test vectors, and decapsulated ss
        0a0768e2475eb7897799ac2e5d3abae0632792cd3d2221ebac2c04fa7cd973fc
        f726c75f8e63da0f59f28130622ef2d67038000d959d632e7053f9b3383be9d3

There's also the open issue of aligning the KEM combiner domain-separator labels, or intentionally not aligning the labels, which is being discussed here: https://github.com/cfrg/draft-irtf-cfrg-concrete-hybrid-kems/pull/15



LAMPS has run out of time, we have to start our WGLC. So this is mostly an advisory that if anyone in the HPKE community has comments on interop with LAMPS, you should raise them during the LAMPS WGLC that I hope will start as soon as I post a new version.


-Mike Ounsworth