Subject: [Cfrg] I-D Action: draft-irtf-cfrg-spake2-04.txt

From: [email-masked]
Date: Mon, 16 Oct 2017 22:40:32 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Crypto Forum RG of the IRTF.

        Title           : SPAKE2, a PAKE
        Authors         : Watson Ladd
                          Benjamin Kaduk
	Filename        : draft-irtf-cfrg-spake2-04.txt
	Pages           : 7
	Date            : 2017-10-16

Abstract:
   This Internet-Draft describes SPAKE2, a secure, efficient password
   based key exchange protocol.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-irtf-cfrg-spake2/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-irtf-cfrg-spake2-04
https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-spake2-04

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-irtf-cfrg-spake2-04

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: Benjamin Kaduk <[email-masked]>
Date: Tue, 17 Oct 2017 06:18:04 -0500

This version is intended to have minimal changes from the -03, and was
intended to un-expire the draft and add me as editor to effect that change.
I want this draft to advance so that it can be used as a reference by
draft-ietf-kitten-krb-spake-preauth.

There is some reformatting due to having to rewrite the source into XML,
and I took advantage of that opportunity to un-wrap the python snippet.

-Ben

On Mon, Oct 16, 2017 at 10:40:32PM -0700, [email-masked] wrote:
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> [email-masked]
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From: Greg Hudson <[email-masked]>
Date: Fri, 20 Oct 2017 13:10:12 -0400

> and I took advantage of that opportunity to un-wrap the python snippet.

Thanks.  I found my old feedback on this draft in
https://www.ietf.org/mail-archive/web/cfrg/current/msg07928.html and
this update resolves one of those issues (the misformatted Python code).

I do not know how to resolve the problem that SPAKE2+ doesn't use w0 or
w1 in the transcript hash, and therefore more closely resembles SPAKE1
than SPAKE2.  I suggest the following edits for the other issues:

* In section 2.2, remove the spaces around the || operators starting
after K.

* In section 2.3, replaces "here Bob" with "here B".

* In the Python code, replace "ec.canon_pointstr" with "canon_pointstr".

* Replace the introductory text of section 3 with:

  Every curve presented in the table below has an OID from [RFC5480].
  We construct a string using the OID and the needed constant, for
  instance "1.3.132.0.35 point generation seed (M)" for P-512.  This
  string is turned into a series of blocks by hashing with SHA256, and
  hashing that output again to generate the next 32 bytes, and so on.
  This pattern is repeated for each group and value, with the string
  modified appropriately.

  A byte string of length equal to that of an encoded group element is
  constructed by concatenating as many blocks as are required,
  starting from the first block, and truncating to the desired length.
  The byte string is then formatted as required for the group.  In the
  case of Weierstrass curves, this means setting the first byte to
  0x02 or 0x03 depending on the low-order bit.  For Ed25519 style
  formats this means taking all the bytes as the representation of the
  group element.  The byte string is then interpreted as an element in
  the group.  If this interpretation yields a valid group element with
  the correct order (p), the byte string is the output.  Otherwise,
  the initial hash block is discarded and the process is repeated
  until a valid element is found.

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From: Benjamin Kaduk <[email-masked]>
Date: Mon, 23 Oct 2017 22:30:01 -0500

Hi Greg,

> than SPAKE2.  I suggest the following edits for the other issues:

Thanks for pulling up your old review comments.  I do plan to go through
the archives to see if there were any other outstanding review comments,
for the next revision.

-Ben

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From: Watson Ladd <[email-masked]>
Date: Tue, 24 Oct 2017 07:33:40 -0700

> than SPAKE2.  I suggest the following edits for the other issues:

Yeah, I'll have to look at the source (SPAKE2+ comes from an upublished
book...)

>   until a valid element is found.

Thanks for you comments

-- 
"Man is born free, but everywhere he is in chains".
--Rousseau.