Verifiable Random Functions (VRFs)
draft-irtf-cfrg-vrf-03

Document Type Active Internet-Draft (cfrg RG)
Last updated 2018-09-14
Replaces draft-goldbe-vrf
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CFRG                                                         S. Goldberg
Internet-Draft                                                 L. Reyzin
Intended status: Standards Track                       Boston University
Expires: March 18, 2019                                  D. Papadopoulos
                           Hong Kong University of Science and Techology
                                                               J. Vcelak
                                                                     NS1
                                                      September 14, 2018

                   Verifiable Random Functions (VRFs)
                         draft-irtf-cfrg-vrf-03

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).

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of

Goldberg, et al.         Expires March 18, 2019                 [Page 1]
Internet-Draft                     VRF                    September 2018

   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Rationale . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  VRF Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  VRF Security Properties . . . . . . . . . . . . . . . . . . .   5
     3.1.  Full Uniqueness or Trusted Uniqueness . . . . . . . . . .   5
     3.2.  Full Collison Resistance or Trusted Collision Resistance    5
     3.3.  Full Pseudorandomness or Selective Pseudorandomness . . .   5
     3.4.  A random-oracle-like unpredictability property  . . . . .   6
   4.  RSA Full Domain Hash VRF (RSA-FDH-VRF)  . . . . . . . . . . .   7
     4.1.  RSA-FDH-VRF Proving . . . . . . . . . . . . . . . . . . .   8
     4.2.  RSA-FDH-VRF Proof To Hash . . . . . . . . . . . . . . . .   8
     4.3.  RSA-FDH-VRF Verifying . . . . . . . . . . . . . . . . . .   9
   5.  Elliptic Curve VRF (ECVRF)  . . . . . . . . . . . . . . . . .  10
     5.1.  ECVRF Proving . . . . . . . . . . . . . . . . . . . . . .  12
     5.2.  ECVRF Proof To Hash . . . . . . . . . . . . . . . . . . .  13
     5.3.  ECVRF Verifying . . . . . . . . . . . . . . . . . . . . .  13
     5.4.  ECVRF Auxiliary Functions . . . . . . . . . . . . . . . .  14
       5.4.1.  ECVRF Hash To Curve . . . . . . . . . . . . . . . . .  14
       5.4.2.  ECVRF Nonce Generation  . . . . . . . . . . . . . . .  21
       5.4.3.  ECVRF Hash Points . . . . . . . . . . . . . . . . . .  22
       5.4.4.  ECVRF Decode Proof  . . . . . . . . . . . . . . . . .  23
     5.5.  ECVRF Ciphersuites  . . . . . . . . . . . . . . . . . . .  23
     5.6.  When the ECVRF Keys are Untrusted . . . . . . . . . . . .  26
       5.6.1.  ECVRF Validate Key  . . . . . . . . . . . . . . . . .  26
   6.  Implementation Status . . . . . . . . . . . . . . . . . . . .  28
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
     7.1.  Key Generation  . . . . . . . . . . . . . . . . . . . . .  28
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