# 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 "- this need not be published in an RFC, the IANA code-point alone is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/