Subject: [Cfrg] I-D Action: draft-irtf-cfrg-vrf-07.txt

From: [email-masked]
Date: Thu, 18 Jun 2020 07:36:23 -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           : Verifiable Random Functions (VRFs)
        Authors         : Sharon Goldberg
                          Leonid Reyzin
                          Dimitrios Papadopoulos
                          Jan Vcelak
	Filename        : draft-irtf-cfrg-vrf-07.txt
	Pages           : 39
	Date            : 2020-06-18

Abstract:
   A Verifiable Random Function (VRF) is the public-key version of a
   keyed cryptographic hash.  Only the holder of the private key can
   compute the hash, but anyone with public key can verify the
   correctness of the hash.  VRFs are useful for preventing enumeration
   of hash-based data structures.  This document specifies several VRF
   constructions that are secure in the cryptographic random oracle
   model.  One VRF uses RSA and the other VRF uses Eliptic Curves (EC).

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

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-irtf-cfrg-vrf-07
https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-vrf-07

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-irtf-cfrg-vrf-07

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/

---

From: Leonid Reyzin <[email-masked]>
Date: Thu, 18 Jun 2020 10:39:03 -0400

Dear CFRG,

Summary: This update removes two of our own hash-to-curve methods and
instead incorporates by reference those of the hash-to-curve draft
<https://datatracker.ietf.org/doc/draft-irtf-cfrg-hash-to-curve/> (many
thanks to Riad Wahby for his assistance with the necessary edits and
technical decisions).

We believe the draft is close to RGLC and would appreciate feedback.

Details: The draft specifies four Elliptic Curve VRF ciphersuites (in
addition to the RSA VRF). The four ciphersuites are based on two curves
with two hash-to-curve methods for each curve. That has not changed. The
update affects all four ciphersuites. Unfortunately, incorporating the
hash-to-curve draft by reference required breaking compatibility with the
previous versions (-03 through -06) of the VRF draft.

More Details: For curve Edwards25519, we replaced our own Elligator2
hash-to-curve method with the one from the hash-to-curve draft, which has
significant differences in hashing and minor differences in arithmetic. For
curve P256, we similarly replaced our own Simplified Shallue-van de
Woestijne-Ulas hash-to-curve method with the one from the hash-to-curve
draft. For both curves, we updated the hash function domain separation for
every use of hashing, in order to ensure that hash functions are
domain-separated from the hash-to-curve draft. This affected also the two
ciphersuites that use our own, non-constant-time, try-and-increment method
of hashing to elliptic curves.

Sincerely,

Sharon, Dimitris, Leo, Jan

On Thu, Jun 18, 2020 at 10:36 AM <[email-masked]> wrote:

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