Shepherd writeup

As required by RFC 4858, this is the current template for the Document 
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

This document defines added Modular Exponential (MODP) Groups for the
Secure Shell (SSH) protocol using SHA-2 hashes. The draft updates RFC4250, 
RFC4253. This is indicated in the header as well as in the abstract and 
the introduction.   

(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  Relevant content can frequently be found in the abstract 
  and/or introduction of the document. If not, this may be 
  an indication that there are deficiencies in the abstract 
  or introduction.

This document defines added Modular Exponential (MODP) Groups for the
Secure Shell (SSH) protocol using SHA-2 hashes.

Working Group Summary

  Was there anything in WG process that is worth noting? For 
  example, was there controversy about particular points or 
  were there decisions where the consensus was particularly 

The document received few reviews on the mailing list. However, 
discussions occur on whether:
    - choosing IKE vs TLS primes
    - choosing fixed primes versus random.  
The consensus for this document was to restraint to the primes defined for IKE.

  Are there existing implementations of the protocol? Have a 
  significant number of vendors indicated their plan to 
  implement the specification? Are there any reviewers that 
  merit special mention as having done a thorough review, 
  e.g., one that resulted in important changes or a 
  conclusion that the document had no substantive issues? If 
  there was a MIB Doctor, Media Type or other expert review, 
  what was its course (briefly)? In the case of a Media Type 
  review, on what date was the request posted?

The draft describes the following key exchange algorithms:
* diffie-hellman-group14-sha256 
* diffie-hellman-group15-sha512 
* diffie-hellman-group16-sha512 
* diffie-hellman-group17-sha512 
* diffie-hellman-group18-sha512 

These suites have been at least partially implemented. [00],[2]
* OpenSSH has implemented and distributed at least diffie-hellman-group14-sha256 it already [0]
* Dropbear has preliminary support for  diffie-hellman-group14-sha256 by Matt Johnston [1] 
* RLogin supports dh-group{14,15,16}-sha256 since version 2.19.8 [3]. 
* Tera Term committed dh-group{14,15,16}-sha256  support committed to trunk, and it will be included in next release. [4] 
* Poderosa [5] committed to support dh-group{14,15,16}-sha256 support where a pull request has been sent  [6]. 

[5] in 


  Who is the Document Shepherd? Who is the Responsible Area

Daniel Migault is the Document Shepherd, Eric Rescola is the 
Responsible Area Director.

(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.

The document shepherd reviewed the document and followed the 
discussion on mailing list and during the meeting. 

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?


(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.


(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.

I have no concerns. 

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.

The author declared he is not aware of any IPR. 

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR


(9) How solid is the WG consensus behind this document? Does it 
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?   

I believe the we reached WG consensus. 

(10) Has anyone threatened an appeal or otherwise indicated extreme 
discontent? If so, please summarise 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.) 

One person strongly disagrees with the statement that fixed primes
are better than random. Although this discussion was not targeting 
the draft and was not opposed to the use of fixed primes for the draft. As
 a result, I see this more as a relevant discussion, than as a opposition
to the draft.  

The "security considerations" section reflects the discussion with the text below:
   Using a fixed set of Diffie-Hellman parameters makes them a high
   value target for precomputation.  Generating additional sets of
   primes to be used, or moving to larger values is a mitigation against
   this issue.  Care should be taken to avoid backdoored primes ([SNFS])
   by using "nothing up my sleve" parameters.

People did not really care on using TLS or IKE primes. 

(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be

The only nit mentioned is the one below. I believe this paragraph can be removed as I do not see material copied from previous document.

  -- The document seems to contain a disclaimer for pre-RFC5378 work, and may
     have content which was first submitted before 10 November 2008.  The
     disclaimer is necessary when there are original authors that you have
     been unable to contact, or if some do not wish to grant the BCP78 rights
     to the IETF Trust.  If you are able to get all authors (current and
     original) to grant those rights, you can and should remove the
     disclaimer; otherwise, the disclaimer is needed and you can ignore this
     comment. (See the Legal Provisions document at for more information.)

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

These reviews were not needed.  

(13) Have all references within this document been identified as
either normative or informative?


(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?


(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in 
the Last Call procedure. 


(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.

The draft updates RFC4250 and RFC4253. These RFC are listed in the header, abstract and introduction. 

(17) 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 protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).

The IANA section is clear. It is consistent with the current draft and 
references have been clearly identified. 

The IANA section details how to update the Key Exchange Method Names table [1].
Registration requires the IETF consensus. There is no expert review. 


(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.

The IANA consideration provides the necessary parameters for the 
IANA registries. IANA registries requires IETF consensus. There is
 no Expert review.

(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

This is not applicable. No checks were performed