Hi John,
On 7/12/26 17:49, John Mattsson wrote:
David Stainton wrote:
No. Let’s not move the discussion away from the draft and from the
extremely relevant context of TLS.
I do not understand why draft-ietf-tls-ecdhe-mlkem, random fields in
TLS and other IETF protocols, all key transport protocols, and the
use of various algorithms (ML-KEM, RSA-OAEP, RSA-PSS, RSA-KEM) in
other IETF protocols would not be considered equally important. I
think modern RSA algorithms also reveals randomness to the peer
similar to ML-KEM.
David Stainton wrote:
I am going to update the golang hpqc library and the katzenpost
mixnet project will take the defense in depth route.
That actually seems compatible with the view that securing the
randomness should be done by the application and not the algorithm.
Note that just hashing gives a very poor protection against
compromised RNGs. If possible you should include some additional
entropy in the hash m = H(m, additional entropy).
Restoring Kyber's hash is safer. The issue is not related to entropy but
structure. I am concerned that you don't accept this distinction and
continue to confuse the two issues. This attack strategy works when the
RNG in question has been fed as much entropy as you'd like to give it.
Simon Josefsson wrote:
If you deviate, such as by taking the defense-in-depth approach to
hash m
Inserting a NIST-approved DRBG such as Hash_DRBG, HMAC_DRBG between
your potentially compromised entropy source and ML-KEM seems
conformant to NIST specifications.
This again mistakes the issue at hand for entropy when it is about
hidden algebraic structure.
Your suggestion is deficient in that the issue is that ML-KEM's `m` is
not robust against different kinds of failures in _the DRBG itself_
including issues such as intentionally hiding structure it the output.
Hashing `m` is more robust than not hashing it against this exact concern.
I appreciate that you have full confidence in the remaining NIST DRBGs
and depending on your threat model(s), they may indeed be sufficient.
I am confident that they are not sufficient in all threat models. I
would rather use a better fast-key erasure design in any case.
Kind regards,
Jacob Appelbaum
Cheers, John Preuß Mattsson
From: David Stainton <[email protected]> Date: Sunday, 12 July
2026 at 16:03 To: Kris Kwiatkowski <[email protected]> Cc:
[email protected] <[email protected]> Subject: [TLS] Re: WG Last Call: draft-
ietf-tls-mlkem-08 (Ends 2026-07-08)
Hi Kris, No. Let’s not move the discussion away from the draft and
from the extremely relevant context of TLS.
Restoring the hash is reasonable and NIST’s removal wasn’t well
motivated or justified, their silence to reasonable questions now is
suspicious when we consider the relevant history.
There may be better designs but they will only slow down deployment.
The best course of action is restoring the hash over m. It lasted
for three rounds without a security issue being found by NIST or
NSA.
I am going to update the golang hpqc library and the katzenpost
mixnet project will take the defense in depth route.
David Stainton Founder and core developer, Katzenpost post quantum
mixnet
On Sun, Jul 12, 2026 at 1:08 PM Kris Kwiatkowski
<[email protected]> wrote:
On 12/07/2026 09:06, John Mattsson wrote:
Regarding Jakob Appelbaum's suggested text, I agree that wording
along the lines of "the m value is recoverable by the
decapsulating peer" should be added to draft-ietf-tls-ecdhe-mlkem,
draft-ietf-tls-mlkem, and likely to future IETF KEM specifications
as well.
I agree with the points below, including that the broader CSPRNG
guidance discussion belongs in a wider IETF context such as an
RFC4086bis effort.
On where the suggested text about 'm' being recoverable by the
decapsulating peer should go: I think draft-sfluhrer-cfrg-ml-kem-
security-considerations is the proper home for it, rather than the
documents that merely define code points for TLS. The TLS drafts
could then simply reference it. Duplicating ML-KEM security
considerations across draft-ietf-tls-ecdhe-mlkem, draft-ietf-tls-
mlkem, and every future KEM code point document seems fragile, and
a single CFRG document keeps the guidance consistent. This follows
the same logic as your RFC4086bis suggestion: put the guidance
where it can be referenced, not in each protocol-specific draft.
For the same reason, the discussion itself belongs in CFRG, where
it would get review from the crowd focused on cryptographic
mechanisms.
Cheers, Kris
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