Hash-based Signatures: State and Backup Management
draft-ietf-pquip-hbs-state-04

[Ballot comment]
Thank you to Peter Yee for his GENART review.  See https://datatracker.ietf.org/doc/review-ietf-pquip-hbs-state-03-genart-lc-yee-2026-02-14/.  He outlines a few areas that would benefit from further clarity.  Please also review his editorial feedback.

I support the DISCUSS position of Deb Cooley.

[Ballot discuss]
Let me start by saying that I absolutely think this specification is needed.  Stateful HBS schemes are useless without a way to backup/transfer a key/state from one hardware device to another securely.  US NIST's SP 800-208 is woefully lacking in this regard.

This discuss should be easy to resolve.  I'm happy to help.

General (background):  Even though there are no BCP14 keywords (BCP 14 keywords are for interoperability, not security), that does not imply that there is no normative language.  In fact, there are 32 'must' statements as well as 23 'should' statements in the draft that are clearly normative.  This is merely an observation, but my comment about the Reference section is more important.

References:  Are there really no Normative References?  Can one read this specification without any of the current references?  I will suggest that at least a portion of these should be Normative References.  Perhaps:  RFCs 8391, 8554, 9802, and SP 800-208.

[Ballot comment]
Thanks to Yaron Sheffer for their secdir review.

Section 2.3, para 2:  I don't understand the phrase 'to avoid state reuse by rolling back to a state in which already-used OTS keys'. Are you intending to roll back to the most recently used state/OTS key?  If so, why?

Section 2.4, key export and key import:  Why is the word (partial) used here?  Under some circumstances is a partial private key imported/exported?  Perhaps the key is imported/exported in multiple parts?  If that is the case, I think it can be ignored, so the '(partial)' type language could be removed.

Section 6: (I fear that this comment will be too late for action) Backup management is the real issue this specification raises.  There is a simple mechanism which might make backup management cleaner.  If one were allowed to store the seed private key in backup hardware, and then recorded state both internal to the current hardware, and on a paper copy for a backup of state.  There would be a process where both internal state and paper copy state are updated prior to a signature being issued.  In the case of catastrophic failure of the hardware is then recoverable with the backup hardware (seed private key) and the paper copy state backup.

[Ballot comment]

# Éric Vyncke INT AD comments for draft-ietf-pquip-hbs-state-03
CC @evyncke

Thank you for the work put into this document (even if most of the content was above my field of expertise).

Please find below some non-blocking COMMENT points/nits (replies would be appreciated even if only for my own education).

I hope that this review helps to improve the document,

Regards,

-éric

Note: this ballot comments follow the Markdown syntax of https://github.com/mnot/ietf-comments/tree/main, i.e., they can be processed by a tool to create github issues.

## COMMENTS (non-blocking)

### Section 1

who is the "we" in `draft-ietf-pquip-hbs-state-03` ? The authors ? the WG ? The IETF ? Please avoid ambiguities (it is not an academic paper ;-) )

Also in other places.

### Section 9

Should the NSA & NIST be qualified by prefixing their names with US ?

Request for IETF Last Call review by GENART Completed: Ready with Issues. Reviewer: Peter Yee. Sent review to list. Submission of review completed at an earlier date.

[Ballot comment]
Hi Thom, Kaveh, Stefan, Jim, and Stavros,

Thank you for the effort put into this document.

## I find this very useful, well-structured, and nuances to the reasoning through the text helpful.

## I appreciate the discussion in the Operational Considerations section, although I have a comment about the form. The text is dense in some part with very long sentences (:-), splitting into sub-sections will help highlight key considerations. I would structure it as follows:

NEW:
# Operational Considerations
## Assessing Operational Costs
## Ensuring Long-lived Resilient Solutions
## Training and Skills
## Configurable Warning Thresholds
## Selection of Appropriate Parameter Set
## External Dependecies

## M-of-N controls

CURRENT:
  Mechanisms also should be put in place to mitigate the
  ever-present insider threat via mechanisms such as M-of-N controls

Maybe consider adding a reference or define these controls.

## I flagged some nits here and there that I will send as a PR for authors convenience.

Cheers,
Med

[Ballot comment]
# Andy Newton, ART AD, comments for draft-ietf-pquip-hbs-state-03
CC @anewton1998

* line numbers:
  - https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-pquip-hbs-state-03.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/

## Thanks to the Reviewers

Thanks to Jiankang Yao for the ARTART review.

## Comments

This is a very interesting document.
I have no objection to it being published as an RFC.

The following Last Call announcement was sent out (ends 2026-02-24):

From: The IESG
To: IETF-Announce
CC: draft-ietf-pquip-hbs-state@ietf.org, paul.hoffman@icann.org, paul.wouters@aiven.io, pqc@ietf.org, pquip-chairs@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Hash-based Signatures: State and Backup Management) to Informational RFC


The IESG has received a request from the Post-Quantum Use In Protocols WG
(pquip) to consider the following document: - 'Hash-based Signatures: State
and Backup Management'
  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 2026-02-24. 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


  Stateful Hash-Based Signature Schemes (Stateful HBS) such as LMS,
  HSS, XMSS and XMSS^MT combine Merkle trees with One-Time Signatures
  (OTS) to provide signatures that are resistant against attacks using
  large-scale quantum computers.  Unlike conventional stateless digital
  signature schemes, Stateful HBS have a state to keep track of which
  OTS keys have been used, as double-signing with the same OTS key
  allows forgeries.

  This document provides guidance and catalogs security considerations
  for the operational and technical aspects of deploying systems that
  rely on Stateful HBS.  Management of the state of the Stateful HBS,
  including any handling of redundant key material, is a sensitive
  topic.  This document describes some approaches to handle the
  associated challenges.  It also describes the challenges that need to
  be resolved before certain approaches should be considered.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-pquip-hbs-state/



No IPR declarations have been submitted directly on this I-D.

Request for IETF Last Call review by ARTART Completed: Almost Ready. Reviewer: Jiankang Yao. Sent review to list. Submission of review completed at an earlier date.

The following Last Call announcement was sent out (ends 2026-01-20):

From: The IESG
To: IETF-Announce
CC: draft-ietf-pquip-hbs-state@ietf.org, paul.hoffman@icann.org, paul.wouters@aiven.io, pqc@ietf.org, pquip-chairs@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Hash-based Signatures: State and Backup Management) to Informational RFC


The IESG has received a request from the Post-Quantum Use In Protocols WG
(pquip) to consider the following document: - 'Hash-based Signatures: State
and Backup Management'
  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 2026-01-20. 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


  Stateful Hash-Based Signature Schemes (Stateful HBS) such as LMS,
  HSS, XMSS and XMSS^MT combine Merkle trees with One-Time Signatures
  (OTS) to provide signatures that are resistant against attacks using
  large-scale quantum computers.  Unlike conventional stateless digital
  signature schemes, Stateful HBS have a state to keep track of which
  OTS keys have been used, as double-signing with the same OTS key
  allows forgeries.

  This document provides guidance and catalogs security considerations
  for the operational and technical aspects of deploying systems that
  rely on Stateful HBS.  Management of the state of the Stateful HBS,
  including any handling of redundant key material, is a sensitive
  topic.  This document describes some approaches to handle the
  associated challenges.  It also describes the challenges that need to
  be resolved before certain approaches should be considered.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-pquip-hbs-state/



No IPR declarations have been submitted directly on this I-D.

Document History

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

There was a fair but not large number of responses to the WG Last Call. There was not noticeable disagreement.

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

There was not significant controversy.

- 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.)

None was suggested.

- 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 recommends) or elsewhere (where)?

This is an operational document.

Additional Reviews

- 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.

Stateful Hash-Based Signature Schemes (Stateful HBS) are discussed in other WGs (particularly LAMPS), and some external organizations. Members of those groups are also members of the PQUIP WG.

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

No such reviews are applicable here.

- If the document contains a YANG module, has the final version of the module been checked with any of the recommended validation tools 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?

There is no YANG module here.

- 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.

There are no checks here.

Document Shepherd Checks

- 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?

needed: yes
clearly written: as much as possible for the topic
complete: yes
correctly designed: yes
ready to be handed off to the responsible Area Director: yes

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

None noted.

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

Informational, because it is about operations. It is not a BCP because it is suggestions based on theory, not proven practice.

- Have reasonable efforts been made to remind all authors of the intellectual property rights (IPR) disclosure obligations described in BCP 79? 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.

Each author replied that they did not know of any IPR related to the document.

- 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.

Yes, and there are five.

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

The remaining nits are non-consequential.

- Should any informative references be normative or vice-versa? See the IESG Statement on Normative and Informative References.
- List any normative references that are not freely available to anyone. Did the community have sufficient access to review any such normative references?
- Are there any normative downward references (see RFC 3967 and BCP 97) that are not already listed in the DOWNREF registry? If so, list them.
- 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 references are informative, as is appropriate.

- 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.

This document does not change the status of any other RFC.

- 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).

It correctly says that there are no IANA actions.

- 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.

None.

Document History

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

There was a fair but not large number of responses to the WG Last Call. There was not noticeable disagreement.

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

There was not significant controversy.

- 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.)

None was suggested.

- 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 recommends) or elsewhere (where)?

This is an operational document.

Additional Reviews

- 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.

Stateful Hash-Based Signature Schemes (Stateful HBS) are discussed in other WGs (particularly LAMPS), and some external organizations. Members of those groups are also members of the PQUIP WG.

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

No such reviews are applicable here.

- If the document contains a YANG module, has the final version of the module been checked with any of the recommended validation tools 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?

There is no YANG module here.

- 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.

There are no checks here.

Document Shepherd Checks

- 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?

needed: yes
clearly written: as much as possible for the topic
complete: yes
correctly designed: yes
ready to be handed off to the responsible Area Director: yes

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

None noted.

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

Informational, because it is about operations. It is not a BCP because it is suggestions based on theory, not proven practice.

- Have reasonable efforts been made to remind all authors of the intellectual property rights (IPR) disclosure obligations described in BCP 79? 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.

Each author replied that they did not know of any IPR related to the document.

- 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.

Yes, and there are five.

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

The remaining nits are non-consequential.

- Should any informative references be normative or vice-versa? See the IESG Statement on Normative and Informative References.
- List any normative references that are not freely available to anyone. Did the community have sufficient access to review any such normative references?
- Are there any normative downward references (see RFC 3967 and BCP 97) that are not already listed in the DOWNREF registry? If so, list them.
- 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 references are informative, as is appropriate.

- 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.

This document does not change the status of any other RFC.

- 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).

It correctly says that there are no IANA actions.

- 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.

None.

Document History

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

There was a fair but not large number of responses to the WG Last Call. There was not noticeable disagreement.

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

There was not significant controversy.

- 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.)

None was suggested.

- 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 recommends) or elsewhere (where)?

This is an operational document.

Additional Reviews

- 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.

Stateful Hash-Based Signature Schemes (Stateful HBS) are discussed in other WGs (particularly LAMPS), and some external organizations. Members of those groups are also members of the PQUIP WG.

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

No such reviews are applicable here.

- If the document contains a YANG module, has the final version of the module been checked with any of the recommended validation tools 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?

There is no YANG module here.

- 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.

There are no checks here.

Document Shepherd Checks

- 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?

needed: yes
clearly written: as much as possible for the topic
complete: yes
correctly designed: yes
ready to be handed off to the responsible Area Director: yes

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

None noted.

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

Informational, because it is about operations. It is not a BCP because it is suggestions based on theory, not proven practice.

- Have reasonable efforts been made to remind all authors of the intellectual property rights (IPR) disclosure obligations described in BCP 79? 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.

I have sent the authors this request on 2025-12-16; I will update this report when I have heard all the responses.

- 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.

Yes, and there are five.

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

The remaining nits are non-consequential.

- Should any informative references be normative or vice-versa? See the IESG Statement on Normative and Informative References.
- List any normative references that are not freely available to anyone. Did the community have sufficient access to review any such normative references?
- Are there any normative downward references (see RFC 3967 and BCP 97) that are not already listed in the DOWNREF registry? If so, list them.
- 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 references are informative, as is appropriate.

- 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.

This document does not change the status of any other RFC.

- 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).

It correctly says that there are no IANA actions.

- 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.

None.