In this message, I am responding collectively to the following
emails: - William Layton (NSA) - Deb Cooley (Sec AD)
Due to the high volume of traffic from this mailing list, I will
create a new email address. I would like to mention this in advance
to avoid any misunderstandings, as the new email address will be
registered before the current one is removed.
William Layton (NSA):
On Tue, 07 July 2026 [1]:
The two independent layers is all about implementation, not
cryptography. If you look at the more detailed solutions that
implement two layers you'll see separate boxes with firewalls,
intrusion detection, etc. placed between them. That concept is
orthogonal to a discussion of multiple algorithms.
My question was:
Why the apparent change of position?
In this PDF document, the NSA consistently requires the exact
opposite: a hybrid approach (two tunnels/layers).
1. The concept of a (parallel) hybrid approach is to safeguard
against failure of a single component. Whether the hybrid approach
is applied across implementation boundaries or across cryptographic
algorithms is irrelevant to the nature of the hybrid approach. In
this case, it safeguards against any (future) compromise of ML-KEM
(or weaknesses associated with it) by also using ECC. Therefore, the
distinction between implementation and cryptography is irrelevant in
this context.
2. Post-quantum algorithms are immature. RFC 9958 (Post-Quantum
Cryptography for Engineers) [2] from June 2026: "the post-quantum
algorithms face uncertainty about the underlying mathematics,
compliance issues, unknown vulnerabilities, and hardware and
software implementations that have not had sufficient maturing time
to rule out traditional cryptanalytic attacks and implementation
bugs." ECC was far better understood and studied at the time it was
standardized. I myself found it surprising how quickly the NIST PQC
standardization process took place. The subsequent cryptanalytic
breaks of several algorithms, including a finalist, are therefore
less surprising.
3. SIKE, a NIST finalist, was shown to be breakable in 2022, only
four years ago. Under these circumstances, cutting away the second
safety belt introduces unnecessary risk.
4. Moreover, contrary to the explicit recommendation of one of the
authors of ML-KEM/Kyber (Peter Schwabe), the hash was removed even
though it would help protect against attacks such as the NSA's
Dual_EC_DRBG backdoor, which NIST was ultimately forced to remove:
"Should those RNGs include the hash? Yes, of course. [...] Of
course, as you stated in a another message, the RNG output may leak
through all kind of other sources, but the hash in Kyber's Ecnaps is
a cheap "defense-in-depth" mechanism to ensure that we don't add
another source of leakage." [3] As the Kyber author mentions
correctly, adding the hash is inexpensive, and removing it without a
compelling justification raises legitimate concerns. Given that the
NSA's contribution was never disclosed ("The FOIA results show that
what NIST publicly labeled as the "Post Quantum Cryptography Team,
National Institute of Standards and Technology (NIST), [email protected]"
actually had more NSA members than NIST members." [4]), these
circumstances warrant careful scrutiny.
5. Anything other than using a hybrid approach here is difficult to
justify from a cryptographic perspective. This is especially true
given the risks outlined above. For these reasons, the hybrid
approach is explicitly recommended in RFC 9958 (Post- Quantum
Cryptography for Engineers) Section 15.4. [5]: "Hybrid key exchange
is recommended to enhance security against the HNDL attack.
Additionally, hybrid signatures provide for time to react in the
case of the announcement of a devastating attack against any one
algorithm, while not fully abandoning traditional cryptosystems."
6. Virtually everyone else has also chosen a hybrid approach. Not
only did OpenSSH adopt a hybrid approach by default in 2022 ("use
the hybrid Streamlined NTRU Prime + x25519 key exchange method by
default (" [email protected]")" [6]), but it also
adopted another hybrid scheme only a few days ago ("OpenSSH 10.4 was
released on 2026-07-06. [...] add experimental support for a
composite post-quantum signature scheme that combines ML-DSA 44 and
Ed25519" [7]). Germany's NIST counterpart, the BSI, reaches the same
conclusion. Technical Guideline TR-02102-2 (version 2026-01): "The
BSI intends to recommend the quantum-safe hybrid key agreement
mechanisms SecP256r1MLKEM768 and SecP384r1MLKEM1024 from the
Internet-Draft at https:// datatracker.ietf.org/doc/ draft- ietf-
tls-ecdhe-mlkem/ as soon as the corresponding RFC has been
adopted." [8] BSI TR-02102-1 (version 2026-01): "The quantum- safe
mechanisms recommended in this Technical Guideline are generally not
yet trusted to the same extent as the established classical
mechanisms, since they have not been as well studied with regard to
side-channel resistance and implementation security. To ensure the
long-term security of a key agreement, this Technical Guideline
therefore recommends the use of a hybrid key agreement mechanism
that combines a quantum- safe and a classical mechanism. An obvious
hybridization is to perform two key agreements in parallel and to
derive a combined key from the generated key material." [9]
There are multiple significant warning signs.
I can only respond intermittently, and lack of response, even for a
longer time, does not mean endorsement. Currently, my resources are
outmatched by those of the NSA.
Deb Cooley (Sec AD):
On Tue, 07 July 2026 15:55 UTC [10]:
This is a public warning to the entire TLS working group, in
accordance
with RFC 3934 Section 2 [0]. [...]
*not participating in ad hominum attacks (veiled or unveiled) *not
sending multiple responses in quick succession
On Tue, 07 July 2026 17:37 UTC [11]:
I will only engage on a couple of points:
1. Obviously those participants who have been contributing in good
faith
have nothing to worry about.
2. The new participants should read the rules prior to posting, this
warning will help them understand what is expected.
RFC 3934 Section 2 [12] explicitly states that a public warning is
the second step after communicating directly with the offending
individual: "Unless the disruptive behavior is severe enough that it
must be stopped immediately, the WG chair should attempt to
discourage the disruptive behavior by communicating directly with
the offending individual. If the behavior persists, the WG chair
should send at least one public warning on the WG mailing list."
I feel it necessary to seek clarification, since the warning and the
subsequent email referring to "[t]he new participants" (plural) were
issued shortly after I entered the mailing list and someone accused
me of an ad hominem attack, although my point clearly concerned a
potential conflict of interest related to NSA activity on this
mailing list, and, in that context, specific actions (or failures to
act) by NSA employees [13].
Andrew Lee made a point [14] with which I agree and which I would
rephrase as follows: an indiscriminate warning can have an
intimidating effect and therefore is detrimental to an open
discussion. The same holds for any vagueness in the interpretation
of rules.
He also wrote:
*not sending multiple responses in quick succession
Participants on both sides have posted multiple messages throughout
this
WGLC. This standard has never previously been cited or enforced.
Further, this warning starves debate during a WGLC; whether that's
intentional or not doesn't matter.
To avoid intimidation and ensure the fair application of the rules,
all parties should strictly adhere to the RFCs and avoid any
uncertainty caused by vague wording.
My understanding is the following:
1. RFC 3934 Section 2 states that, in the case of disruptive
behavior, the WG (working group) chair should first contact the
individual directly. Ideally, the relevant passage should be quoted
and the reason explained.
2. RFC 3934 Section 2 states that a public warning should be issued
by the WG chair only as a second step, and the wording implies that
the individual should be identified in the public warning (and also
not to intimidate others).
3. RFC 3934 Section 2 states that neither individual correspondence
nor a public warning should be conducted by the AD (Area Director),
but by the WG chair.
4. RFC 3934 Section 2 does not state that "new participants" should
be greeted with a warning message.
5. The term "contributing in good faith" is subject to
interpretation, and in order to avoid intimidation, any person to be
warned should be mentioned by name instead. For example, not only
many researchers, but probably the majority of the world population
would reasonably question whether the pervasive NSA presence in this
working group qualifies as "contributing in good faith."
6. Discussions about conflict of interest related to the NSA,
including their behavior on this mailing list with regard to a
potential conflict of interest - as NSA employees, not as members of
a specific ethnicity or some other outward property - constitute
neither an ad hominem attack nor some other violation of any rule.
7. The criterion "not sending multiple responses in quick
succession" is not part of any RFC, as the RFCs define criteria
based on content rather than frequency (e.g., RFC 3683 Section 1
[15] mentions "unsolicited bulk e-mail" or "discussion of subjects
unrelated to IETF policy" etc.). (If a numerical criterion is
unavoidable, it should be exactly defined, e.g., more than two
emails per hour.) I find such a vague formulation problematic, as I
sometimes edit several emails in parallel, and later send them at
the same time, which would formally satisfy the criterion "sending
multiple responses in quick succession" although my overall email
volume is no higher than that of others.
8. An AD (Area Director) who has retired from the NSA after 35+
years no less than three years ago [16] and published RFC 9151 in
2022 as an NSA employee [17] would present a conflict of interest
when dealing with questions concerning the NSA, including whether a
debate constitutes a legitimate discussion of a conflict of interest
related to the NSA. In such a case, that AD should therefore recuse
themselves in accordance with RFC 7776 Section 7 (Conflicts of
Interest) [18]: "Furthermore, a conflict of interest arises if the
person involved in the process of handling a harassment report is
closely associated personally or through affiliation with any of the
Reporter, Respondent, or Subject. / For the avoidance of doubt,
recusal in this context means completely stepping out of any
advisory or decision-making part of any process associated with
handling a harassment report, remedy arising from a harassment
report, or appeal into the handling of a harassment report. That
means that a recused person has no more right to participate in or
witness the process than any other person from the community in the
same situation." One example of a potential conflict of interest is
the publication of an RFC authored solely by an NSA employee [17].
When NSA announced Suite B Cryptography in 2005 and published the
corresponding webpage in 2009 [19], the obvious strategy was to make
the security levels of 128 bits of security (e.g., curve P-256) and
192 bits of security (e.g., curve P-384) publicly available as Suite
B, but withhold the security level of 256 bits of security (e.g.,
curve P-521) as part of Suite A [19, 20, 21]. (From the beginning,
only AES-256 was used to "to enhance interoperability" [22], and in
August 2015, the security level of 128 bits of security was removed
[23].) This may explain why RFC 9151 Section 5.1 [24] lists only
curve P-384 (192 bits of security) as the sole acceptable curve
without providing a rationale in Section 8 (Security Considerations)
[25] for this limitation. While providing a minimum security (a
lower bound) for commercial applications is a legitimate concern,
establishing a limitation (an upper bound) by withholding 256 bits
of security is not. RFC 8890 clearly says "The Internet is for End
Users" [26], and this means strong cryptography (256 bits of
security) should be available for everyone. Notably, Bernstein
explicitly praises curve P-521 (256 bits of security): "To be fair I
should mention that there's one standard NIST curve using a nice
prime, namely 2^521−1" [27].
Please confirm this understanding or, if you disagree, provide an
explanation or clarification.
It would be helpful if every email received from the mailing list
included a permanent archive link in its signature, so that
participants do not have to search the archives manually when
quoting previous messages.
Kind regards,
Ken Kubota
____________________________________________________
Ken Kubota https://doi.org/10.4444/100
[1] https://mailarchive.ietf.org/arch/msg/
tls/5lGA_ObJ5Z58PqIRyF8nC3Lj1Po/
[2] https://www.rfc-editor.org/rfc/rfc9958.html#name-post- quantum-
and-traditiona
[3] https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/
WFRDl8DqYQ4/m/o2XJ2YvfAwAJ
[4] https://nist.pqcrypto.org/foia/highlights.html
[5] https://www.rfc-editor.org/rfc/rfc9958.html#name-hybrid-key-
exchange-and-sig
[6] https://www.openssh.org/txt/release-9.0
[7] https://www.openssh.org/txt/release-10.4
[8] https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/
Publications/TechGuidelines/TG02102/BSI-TR-02102-2.pdf?
__blob=publicationFile&v=11#page=12
[9] https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/
Publications/TechGuidelines/TG02102/BSI-TR-02102-1.pdf?
__blob=publicationFile&v=14#page=29
[10] https://mailarchive.ietf.org/arch/msg/tls/hBFfH4lHo-
cLPNfikGfxkoV6hAY/
[11] https://mailarchive.ietf.org/arch/msg/tls/X44P3cF-H4s8kX-
RzyZEeQYTkbo/
[12] https://www.rfc-editor.org/rfc/rfc3934.html#section-2
[13] https://mailarchive.ietf.org/arch/msg/tls/
xTiYQnK8uS181kRlFe7xiFjdD20/
[14] https://mailarchive.ietf.org/arch/msg/tls/
LvUiinuyMPCXTFMrbeYB0aa1Iw4/
[15] https://www.rfc-editor.org/rfc/rfc3683.html#section-1
[16] https://datatracker.ietf.org/person/Deb%20Cooley "Deb Cooley
Pronouns: she/her
Retired Senior Cryptographic Vulnerability Analyst, National
Security Agency Cybersecurity Directorate (NSA/CSD) with 37+ years
of service in Dec 2023. Most of Deb’s career was spent as a security
evaluator on many different technologies including IP encryptors,
satellites, radios, and key management devices.
Previously, Special Government Expert for the Department of Homeland
Security, Cybersecurity and Infrastructure Security Agency’s Cyber
Security Division. Previously, acme working group chair."
[17] https://www.rfc-editor.org/rfc/rfc9151.html "Published: April
2022 Author: D. Cooley NSA"
"Author's Address
Dorothy Cooley National Security Agency Email: [email protected]"
[18] https://www.rfc-editor.org/rfc/rfc7776.html#section-7
[19] https://web.archive.org/web/20090117004931/http:// www.nsa.gov/
ia/programs/suiteb_cryptography/index.shtml
[20] https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
nistspecialpublication800-56ar.pdf#page=30
[21] https://csrc.nist.gov/files/pubs/fips/186-3/final/docs/
fips_186-3.pdf#page=101
[22] https://web.archive.org/web/20090117004931/http:// www.nsa.gov/
ia/programs/suiteb_cryptography/index.shtml "1. CNSSP-15 correctly
states that 192-bit AES keys are sufficient for
protecting even TOP SECRET information. However, Suite B uses only
256-bit keys to enhance interoperability."
[23] https://web.archive.org/web/20150815072948/https://
www.nsa.gov/ia/programs/suiteb_cryptography/index.shtml
[24] https://www.rfc-editor.org/rfc/rfc9151.html#section-5.1
[25] https://www.rfc-editor.org/rfc/rfc9151.html#section-8
[26] https://www.ietf.org/rfc/rfc8890.html
[27] https://web.archive.org/web/20260628050821/https://
blog.cr.yp.to/20140323-ecdsa.html
Am 07.07.2026 um 23:54 schrieb [email protected]
<[email protected]>:
The two independent layers is all about implementation, not
cryptography. If you look at the more detailed solutions that
implement two layers you'll see separate boxes with firewalls,
intrusion detection, etc. placed between them. That concept is
orthogonal to a discussion of multiple algorithms.
Get Outlook for Android
From: Ken Kubota <[email protected]> Sent: Tuesday, July 7, 2026
5:47:51 PM To: William Layton (GOV) <[email protected]>
Cc: [email protected] <[email protected]> Subject: Re: [TLS] WG Last Call:
draft-ietf-tls-mlkem-08 (Ends
2026-07-08)
Why the apparent change of position?
In this PDF document, the NSA consistently requires the exact
opposite:
a hybrid approach (two tunnels/layers).
"The security against a passive attack targeting Data in
Transit (DiT) across Public Black networks is provided by the
layered encryption of two independent tunnels (Inner and Outer)
using a specific selection of security protocols as instructed
in each CP. The two independent Encryption Components provide
confidentiality and high-level assurance for the solution, because
the adversary should never be able to exploit a single
cryptographic implementation to compromise both tunnels.
Two layers of Data at Rest (DAR) Commercial National Security
Algorithm (CNSA) encryption are employed to provide confidentiality
and mitigate passive attacks of stored data. The DAR components are
independent in a number of ways to mitigate the ability of an
adversary to exploit a single cryptographic implementation to
compromise both layers."
This document is available at:
https://web.archive.org/web/20260425180701/https://www.nsa.gov/
portals/75/documents/resources/everyone/csfc/threat-prevention.pdf
It is also still available on the NSA website.
Originally referenced in:
https://mailarchive.ietf.org/arch/msg/spasm/ytjNpbERE-YgKw-7c_w-
ZRUA1Fw/
The questions raised there remained unanswered:
https://mailarchive.ietf.org/arch/msg/spasm/
WJMl6inph8t8m898kcBzhpWZC0o/
Kind regards,
Ken Kubota
____________________________________________________
Ken Kubota https://doi.org/10.4444/100
Am 07.07.2026 um 22:08 schrieb [email protected]
<[email protected]>:
I support publication. Implementors will make their own decisions.
This algorithm choice
looks likely to be implemented in multiple places, so having
clear documentation of both security considerations and technical
details (as provided by the draft) is worthwhile for those who might
choose to use it.
-Bill _______________________________________________ TLS mailing
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