Secure Shell (SSH) Key Exchange Method Using Hybrid Streamlined NTRU Prime sntrup761 and X25519 with SHA-512: sntrup761x25519-sha512
draft-ietf-sshm-ntruprime-ssh-06

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-sshm-ntruprime-ssh and RFC 9941, changed IESG state to RFC Published)

[Ballot comment]
Thank you to Christer Holmberg for the GENART review
.
** Is there a better source for this critical normative reference – it is currently a personal website.  Is there a DOI number?
[NTRUPrimePQCS]
              Bernstein, D.J., Brumley, B. B., Chen,, M.,
              Chuengsatiansup, C., Lange, T., Marotzke, A., Peng, B.,
              Tuveri, N., Vredendaal, C. V., and B. Yang, "NTRU Prime:
              round 3", WWW https://ntruprime.cr.yp.to/nist/ntruprime-
              20201007.pdf, October 2020.

[Ballot comment]
# Orie Steele, ART AD, comments for draft-ietf-sshm-ntruprime-ssh-05
CC @OR13

* line numbers:
  - https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-sshm-ntruprime-ssh-05.txt&submitcheck=True

* comment syntax:
  - https://github.com/mnot/ietf-comments/blob/main/format.md

* "Handling Ballot Positions":
  - https://ietf.org/about/groups/iesg/statements/handling-ballot-positions/

## Comments

### SSH_DISCONNECT_KEY_EXCHANGE_FAILED: Why not MUST?

I'm sure this has been discussed by the WG, but:

```
134   keys Q_C or Q_S are not the expected lengths.  An abort for these
135   purposes is defined as a disconnect (SSH_MSG_DISCONNECT) of the
136   session and SHOULD use the SSH_DISCONNECT_KEY_EXCHANGE_FAILED reason
137   for the message, see section 11.1 (Disconnection Message) of
138   [RFC4253].  No further validation is required beyond what is
```

Which other reason codes are appropriate for this?

### Ok to Implement?

```
193   Since sntrup761x25519-sha512 is expected to offer no reduction of
194   security compared to curve25519-sha256, it is recommended that it is
195   used and preferred whenever curve25519-sha256 is used today, when the
196   extra communication size and computational requirements are
197   acceptable.
```

```
213   IANA is requested to add a new "Method Name" of
214   "sntrup761x25519-sha512" to the "Key Exchange Method Names" registry
215   for Secure Shell (SSH) Protocol Parameters [IANA-KEX] with a
216   "reference" field to this RFC and the "OK to implement" field of
217   "SHOULD".
```

The security considerations recommends "sntrup761x25519-sha512" over "curve25519-sha256" but the IANA guidance for both algorithms is "SHOULD".

I've seen discussion of this topic on the lists.

Per https://www.rfc-editor.org/rfc/rfc9142.html#section-3.1.3-4

```
Table 8 lists algorithms as "SHOULD" where implementations may be more efficient or widely deployed. The items listed as "MAY" in Table 8 are potentially less efficient.
```

...


```
Methods that are newer or considered to be stronger usually require more device resources than many administrators and/or developers need are to be allowed ("MAY"). (Eventually, some of these methods could be moved by consensus to "SHOULD" to increase interoperability and security.) Methods that are not "weak" and have implementation consensus are encouraged ("SHOULD"). There needs to be at least one consensus method promoted to a status of mandatory to implement (MTI). This should help to provide continued interoperability even with the loss of one of the now disallowed MTI methods.
```

If the working group believes that both methods are equally widely deployed and equally efficient, SHOULD seems correct to me.

I don't see how a WG can conclude that a PQ/T hybrid will be more widely deployed or more efficient than one of its traditional algorithm components, but I am not an expert on SSH.

I'd advise the WG to make this a "MAY", and to tackle clarifying the guidance this registry is trying to provide in a separate document.

I'm not recommending MAY for any reason other than I had to read RFC 9142 to understand what "Ok to implement" means.

The arguments raised regarding PQ migration and harvest now decrypt later are important.

However, I do not believe they justify reading a column in a registry differently for hybrids, even if there is a some chance of a security benefit from doing so.

## Nits

### Acknowledgements before security considerations

```
156 4.  Acknowledgements
```

Typically this comes at the end of the document, although I noted that RFC4251 put contributors after the introduction.

[Ballot comment]
The discussions around SHOULD/MAY have drawn a lot of attention, and I am surprised to see a SHOULD value here compared to the reasons given for other values in RFC9142. However, the distinction is small in practice -- it's not prohibited and not mandated. Thus, I don't see a reason to block further on that.

In Section 1, should "The variant sntrup761 instance" be "The variant sntrup761" or "The sntrup761 instance"? Otherwise, I'm uncertain what a "variant instance" is in this context.

I appreciate the acknowledgement that you've patterned this draft after RFC8731, but this doesn't seem to be useful information in the Introduction. You're already referencing that RFC extensively in the process of building a hybrid; it's unclear that this final statement in the Introduction adds anything.

===NITS FOLLOW===

Section 3: "procedure re-use" => "procedure re-uses"

[Ballot comment]
Thanks for the hard work and the discussions on this I-D.

Balloting an ABSTAIN rather than NoObjection as I have two reservations (see below) on this I-D in its current form but they are not DISCUSS worthy. Please note that for an informational draft, ABSTAIN is like a NoObjection regarding the IESG evaluation.

My first issue is the third consensus call *during* the IESG evaluation, using an *unclear email subject*, with a duration of 4 days... At least, the 3rd consensus call confirmed the 2nd consensus.

My second issue is more fundamental: this I-D specifies an algorithm that must be negotiated and *interoperable* between clients and servers, i.e., it should really be "standards track" and not "informational". The latter would have been OK in the ISE stream to document the "sn..512@openssh.com" but not the official IANA entry of "sn...512".

Normal COMMENTS:

Abstract: unsure whether the IETF can write `This document describes a *widely* deployed` without citing a reference (as it then seems like an advertisement for an implementation).

Section 1: if this document is informational, then `This document *specifies* a hybrid construction` is not correct: it should use "describes" rather than "specifies".

Section 3: s/Some earlier implementation may /Some earlier implementation*s* may /

Section 4: who is the "we" in `We wish to thank` ? The authors (I guess)? the SSH WG ? the IETF ? Please be specific.

Section 4: does the list after `who contributed` mean that the identified people are actual contributors (in the IETF sense == provided a lot of text ?).

[Ballot comment]
Thanks for the discussion on my concerns and giving me the confidence on mlkem768x25519-sha256 getting the same OK-to-implement status and that the WG will work on updating the IANA SSH Registration Policies to align with the fact that there is an SSH WG now for future algorithm discussions.

I have updated my ballot to No Objection.

[Ballot comment]
Thank you for documenting this an Informational I-D.

It's a pity there is a normative reference to a PDF document, rather than an archived source, but for this particular, I-D I shall not worry about that.

[Ballot discuss]
I am balloting DISCUSS, because of the lack of consensus of the current
draft, and its odd Informational Status combined with the "OK-to-implement"
field which is used as a Mandatory-To-Implement (MTI) declaration, resulting
in an Informational Document using a Standards Track action of "MTI".

This document's last calls generated about 100 messages:
https://mailarchive.ietf.org/arch/browse/ssh/?q=ntruprime%20wglc

This document went through two WGLCs, after the first WGLC was appealed
by Eric Rescorla. I agree with his grounds of appeal.
https://mailarchive.ietf.org/arch/msg/ssh/8cTqj-LH_LxUBDWjr8lTjId3mRQ/

There was clearly no consensus. Participants are strongly divided into
two groups. The discussion was heated, and a number of participants
left the discussion as it became combative, tilting results to the
proponents. This makes a consensus call even harder to evaluate, and in
my opinion should be taken into account for the final outcome of both
the intended status of the document and the MTI status.

The opinions between the two WGLCs did not really change, other than
one or two public votes. I also received a private message of someone
who said he was tallied (by a WG member counting votes) into the wrong
column, but they did not want/dare speak out publicly (I can share the
name with AD or WG Chairs). I feel that Eric's appeal grounds are still
valid after the second WGLC was run.

To summarize my objections:

1) There is no consensus for this document to have a SHOULD for MTI

2) It is odd that an Informational document has a MTI other than MAY

3) There seemed to be consensus for all post quantum algorithms to get
  the same MTI status, similar to TLS. But making this document a SHOULD
  would mean all other post quantum algorithms would need a SHOULD as well,
  or for that consensus to be violated.

4) This crypto algorithm is not used in any current IETF protocol, and the
  Crypto Panel review was negative about using this algorithm (which lead
  to the AD Sponsor route with a previous SEC AD being aborted)

5) The deployment of the SSH protocol is strongly biased towards the one
  dominant implementation. This has been the argument used for the MTI
  status. However, use of postquantum algorithms is first and foremost
  to defend against "store now, decrypt later" attacks. As of April 2025,
  with the release of OpenSSH 10.0, the NTRUprime algorithm default has
  been replaced with mlkem:
  From https://www.openssh.com/releasenotes.html

  "the hybrid post-quantum algorithm mlkem768x25519-sha256 is now used
    by default for key agreement."

  This means that the main arguments to promote NTRUprime are not longer
  valid, as soon the usage of NTRUprime will become zero. And having a
  fallback algorithm does not defend against the "store now, decrypt later"
  attack in the case mlkem would have failed.

6) Due to the SSH protocol's use of "vendor namespaces", everyone who
  wants to can already implement any algorithm, and before this document's
  use of the non-vendorized ("IETF") namespace, everyone is running
  this algorithm already in the openssh vendor namespace. I believe the
  IETF namespace should be reserved for algorithms that the IETF strongly
  recommends (eg MTI SHOULD or MUST), but this algorithm does not satisfy
  these constrains.

  During the documents lifetime, I proposed to fix the IANA SSH Registry that
  was updated via RFC 9519 but did not take into account the easy availability
  of "vendor namespaces" with updated Registry Policies, and with a fix to
  rename the odd "OK-to-Implement", which was clearly a field originally
  meant for deprecation of no longer safe algorithms, to a proper MTI field.
  This was not taken into consideration.


If this document would change the OK-to-implement field to MAY, that would
resolve my DISCUSS. I would still think inclusion into the IETF namespace
is a bit of a wrong signal, but I think that would be tolerable. Forcing
people to implement NTRUprime this late in its deployment cycle when it is
basically in its sunset phase, is not the forward thinking we are expecting
from an RFC document (that is not, but pretends to be, a Standards Track
document)

[Ballot comment]
Hi Markus, Jan, and Simon,

Thank you for the effort put into documenting this.

Thanks to Susan Hares for an early OPSDIR review of the individual draft.

Special thanks to Job Snijders for the detailed write-up and description of the development of this document.

I have one minor comment:

# Consider citing a reference

CURRENT:
  The variant sntrup761 instance has been implemented
  widely.

Cheers,
Med

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-sshm-ntruprime-ssh-04. If any part of this review is inaccurate, please let us know.

IANA understands that, upon approval of this document, there is a single action which we must complete.

In the Key Exchange Method Names registry in the Secure Shell (SSH) Protocol Parameters registry group located at:

https://www.iana.org/assignments/ssh-parameters/

the existing registration for:

Method Name: sntrup761x25519-sha512
Note:
OK to Implement: SHOULD

will have its reference changed to [ RFC-to-be ].

We understand that this is the only action required to be completed upon approval of this document.

NOTE: The action requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the action that will be performed.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2025-07-28):

From: The IESG
To: IETF-Announce
CC: debcooley1@gmail.com, draft-ietf-sshm-ntruprime-ssh@ietf.org, job@sobornost.net, ssh@ietf.org, sshm-chairs@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Secure Shell (SSH) Key Exchange Method Using Hybrid Streamlined NTRU Prime sntrup761 and X25519 with SHA-512: sntrup761x25519-sha512) to Informational RFC


The IESG has received a request from the Secure Shell Maintenance WG (sshm)
to consider the following document: - 'Secure Shell (SSH) Key Exchange Method
Using Hybrid Streamlined NTRU
  Prime sntrup761 and X25519 with SHA-512: sntrup761x25519-sha512'
  as Informational RFC

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2025-07-28. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  This document describes a widely deployed hybrid key exchange method
  in the Secure Shell (SSH) protocol that is based on Streamlined NTRU
  Prime sntrup761 and X25519 with SHA-512.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-sshm-ntruprime-ssh/


The following IPR Declarations may be related to this I-D:

  https://datatracker.ietf.org/ipr/6544/

# Document Shepherd Write-Up for draft-ietf-sshm-ntruprime-ssh-03

Overview: this document has been controversial and its processing
in the IETF both before and after the formation of the SSHM WG.
The controversy has multiple bases and dimensions, some of which are
related, some independently controversial, but the starting points are:

- The I-D specifies a mechanism to protect against potential
  "record-now-decrypt-later" attacks from the future invention of a
  cryptographically relevant quantum computer (CRQC). Consensus exists in
  the IETF such protections are a desirable feature in security protocols.

- The specification itself is clear, implemented by multiple parties, and widely
  available through numerous operating system distributions.

- This specific mechanism has been deployed as the default KEX by some SSH
  implementations (incl. OpenSSH) for about 5 years and so has seen widespread
  use, it is expected to continue to be used for maybe a decade to come.

The controversy involved:

- This specific mechanism is based on an algorithm (NTRU Prime) that has not
  been selected as a "winner" in the NIST post-quantum competition. It should
  be noted that NTRU Prime has no known weaknesses and a fairly long history in
  the cryptographic community; the SSHM WG has other drafts in the pipeline to
  handle NIST "winners" but how to signal IETF or WG preferences in this space
  is inherently tricky.

- (valid) opinions in the IETF differ markedly as to whether or not publishing an
  RFC that defines how to use a protocol (like SSH) with a specific algorithm
  (like NTRU), especially in the case where the combination is not expected to be
  a preferred/default (the combination defined here needs to be included in an IANA
  registry and that has happened already).

As a result we have reasoned and reasonable opinions from well-informed WG
participants (and others who care about the generalisation of these topics),
ranging anywhere on the spectrum from:

... "- this MUST be a mandatory-to-implement thing" ...

to

... "- this need not be published in an RFC, the IANA code-point alone is sufficient (or maybe better)" ...

We also have participants preferring almost all opinions in between the above,
some strongly, some weakly.

Any change to intended RFC status or to RFC 2119 terms in this document is
likely to spawn an extended and largely pointless (re-)discussion, so we
(the WG chairs) would strongly encourage not going there during IESG review.
Please ask the SEC ADs or WG chairs before suggesting such. (Though we may well
get the discussion anyway during IETF last call, or maybe people will conclude
that we've already said all that's to be said, which is the case :-)

Paul Wouters indicated to the SSH WG chairs he'd abstain once this document
reaches the IESG.

Lastly the chairs also have observed some historic and personnel based issues
that have caused friction - even well-intentioned apparently trivial suggested
changes may trigger yet more friction.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

See the overview above.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

See the overview above. Consensus on the spec is clear. Consensus on all
RFC 2119 terms is rough, but we got there in the end.

Relevant chair summaries:

29/01/2025 https://mailarchive.ietf.org/arch/msg/ssh/5Plc5CBkNJ-D4Ds26k-OF49Fi4g/
01/03/2025 https://mailarchive.ietf.org/arch/msg/ssh/NU4KkOw-kqLh39PeIgzbuBTos90/

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

See the overview above.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

We've already had an appeal of the 1st WGLC, to the responsible AD and
processed that, related to the RFC 2119 terms.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

Widely implemented, selected as the default KEX in OpenSSH, for about 5 years.
It'll no longer be the default KEX going forward, but will continue to be
supported and used for many years to come.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

N/A. Technically, this is SSH-internal. Politically, this touches loads
of things but additional review is not really needed, nor will it be
useful.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

N/A.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Informational. Yes, datatracker state reflects the intent.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

In-progress, the SSHM chairs do not expect obstacles here.
See https://mailarchive.ietf.org/arch/msg/ssh/S3Vhfm-HW0MOJwq9eHBkVN0w7Ds/

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

In-progress. We don't forsee obstacles here.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

Seems fine. Some "weird spacing" nits for parts of hexadecimal dumps in included
test vectors, but those'll either be fine or be fixed by the RFC editor.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All good.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

All good.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

All good.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

All good.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No status change for existing RFCs.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

All good. Also see the overview.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

# Document Shepherd Write-Up for draft-ietf-sshm-ntruprime-ssh-03

Overview: this document has been controversial and its processing
in the IETF both before and after the formation of the SSHM WG.
The controversy has multiple bases and dimensions, some of which are
related, some independently controversial, but the starting points are:

- The I-D specifies a mechanism to protect against potential
  "record-now-decrypt-later" attacks from the future invention of a
  cryptographically relevant quantum computer (CRQC). Consensus exists in
  the IETF such protections are a desirable feature in security protocols.

- The specification itself is clear, implemented by multiple parties, and widely
  available through numerous operating system distributions.

- This specific mechanism has been deployed as the default KEX by some SSH
  implementations (incl. OpenSSH) for about 5 years and so has seen widespread
  use, it is expected to continue to be used for maybe a decade to come.

The controversy involved:

- This specific mechanism is based on an algorithm (NTRU Prime) that has not
  been selected as a "winner" in the NIST post-quantum competition. It should
  be noted that NTRU Prime has no known weaknesses and a fairly long history in
  the cryptographic community; the SSHM WG has other drafts in the pipeline to
  handle NIST "winners" but how to signal IETF or WG preferences in this space
  is inherently tricky.

- (valid) opinions in the IETF differ markedly as to whether or not publishing an
  RFC that defines how to use a protocol (like SSH) with a specific algorithm
  (like NTRU), especially in the case where the combination is not expected to be
  a preferred/default (the combination defined here needs to be included in an IANA
  registry and that has happened already).

As a result we have reasoned and reasonable opinions from well-informed WG
participants (and others who care about the generalisation of these topics),
ranging anywhere on the spectrum from:

... "- this MUST be a mandatory-to-implement thing" ...

to

... "- this need not be published in an RFC, the IANA code-point alone is sufficient (or maybe better)" ...

We also have participants preferring almost all opinions in between the above,
some strongly, some weakly.

Any change to intended RFC status or to RFC 2119 terms in this document is
likely to spawn an extended and largely pointless (re-)discussion, so we
(the WG chairs) would strongly encourage not going there during IESG review.
Please ask the SEC ADs or WG chairs before suggesting such. (Though we may well
get the discussion anyway during IETF last call, or maybe people will conclude
that we've already said all that's to be said, which is the case :-)

Paul Wouters indicated to the SSH WG chairs he'd abstain once this document
reaches the IESG.

Lastly the chairs also have observed some historic and personnel based issues
that have caused friction - even well-intentioned apparently trivial suggested
changes may trigger yet more friction.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

See the overview above.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

See the overview above. Consensus on the spec is clear. Consensus on all
RFC 2119 terms is rough, but we got there in the end.

Relevant chair summaries:

29/01/2025 https://mailarchive.ietf.org/arch/msg/ssh/5Plc5CBkNJ-D4Ds26k-OF49Fi4g/
01/03/2025 https://mailarchive.ietf.org/arch/msg/ssh/NU4KkOw-kqLh39PeIgzbuBTos90/

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

See the overview above.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

We've already had an appeal of the 1st WGLC, to the responsible AD and
processed that, related to the RFC 2119 terms.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

Widely implemented, selected as the default KEX in OpenSSH, for about 5 years.
It'll no longer be the default KEX going forward, but will continue to be
supported and used for many years to come.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

N/A. Technically, this is SSH-internal. Politically, this touches loads
of things but additional review is not really needed, nor will it be
useful.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

N/A.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Informational. Yes, datatracker state reflects the intent.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

In-progress, the SSHM chairs do not expect obstacles here.
See https://mailarchive.ietf.org/arch/msg/ssh/S3Vhfm-HW0MOJwq9eHBkVN0w7Ds/

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

In-progress. We don't forsee obstacles here.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

Seems fine. Some "weird spacing" nits for parts of hexadecimal dumps in included
test vectors, but those'll either be fine or be fixed by the RFC editor.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All good.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

All good.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

All good.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

All good.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No status change for existing RFCs.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

All good. Also see the overview.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/