Subject: [Lwip] I-D Action: draft-ietf-lwig-curve-representations-17.txt

From: [email-masked]
Date: Fri, 11 Dec 2020 08:14:18 -0800

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Light-Weight Implementation Guidance WG of the IETF.

        Title           : Alternative Elliptic Curve Representations
        Author          : Rene Struik
	Filename        : draft-ietf-lwig-curve-representations-17.txt
	Pages           : 136
	Date            : 2020-12-11

Abstract:
   This document specifies how to represent Montgomery curves and
   (twisted) Edwards curves as curves in short-Weierstrass form and
   illustrates how this can be used to carry out elliptic curve
   computations using existing implementations of, e.g., ECDSA and ECDH
   using NIST prime curves.  We also provide extensive background
   material that may be useful for implementers of elliptic curve
   cryptography.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-lwig-curve-representations/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-ietf-lwig-curve-representations-17
https://datatracker.ietf.org/doc/html/draft-ietf-lwig-curve-representations-17

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-lwig-curve-representations-17

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---

From: Rene Struik <[email-masked]>
Date: Fri, 11 Dec 2020 13:31:15 -0500

Dear colleagues:

I updated the draft, mostly reconsidering iana-related sections. I may 
update once more, depending on what I hear back from expert review.

Small updates:
- added cautionary note re use of signature schemes with message 
encoding/decoding scheme (Section 10.2.1 - ECDSA25519/ECDSA448 with COSE);
- added cautionary language to reflect this in security consideration 
section;
- added step in in Example 4.1, where shared key (curve point) is 
converted to shared secret (octet string). Note: this was already 
spelled out in the COSE/JOSE sections, but thought to add this for 
clarity/avoiding confusion throughout also in specification of ECDH25519 
(Section 4.1);
other:
- added definition of quadratic twist (in curve nomenclature section 
Appendix B.1, with cross-reference to Annex A (added one-liner for each 
of three curve models);
- added one more sentence re twisted curves being a group only under 
certain conditions (triggered by dispelling myths in other standards 
groups) (end of Appendix A.3);
- added informative note on how co-factor DH relates to X25519 and X448 
(end of Section 4.1, resp. Section 4.4), so that readers better 
appreciate differences and similarities;
- tiny word-smything ("i.e.", vs. "e.g." use; "type" vs. "case" language).
   {this is all just simple service to community, so that others can 
reuse definitions in future without much ado}

Rene

On 2020-12-11 11:14 a.m., [email-masked] wrote:
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