RSA Blind Signatures
draft-wood-cfrg-rsa-blind-signatures-00

Document Type Active Internet-Draft (individual)
Authors Frank Denis  , Frederic Jacobs  , Christopher Wood 
Last updated 2021-03-08
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Network Working Group                                           F. Denis
Internet-Draft                                               Fastly Inc.
Intended status: Informational                                 F. Jacobs
Expires: 9 September 2021                                     Apple Inc.
                                                               C.A. Wood
                                                              Cloudflare
                                                            8 March 2021

                          RSA Blind Signatures
                draft-wood-cfrg-rsa-blind-signatures-00

Abstract

   This document specifies the RSA-based blind signature scheme with
   appendix (RSA-BSSA).  RSA blind signatures were first introduced by
   Chaum for untraceable payments [Chaum83].  It extends RSA-PSS
   encoding specified in [RFC8017] to enable blind signature support.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/chris-wood/draft-wood-cfrg-blind-signatures.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 9 September 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Denis, et al.           Expires 9 September 2021                [Page 1]
Internet-Draft            RSA Blind Signatures                March 2021

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   extracted from this document must include Simplified BSD License text
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Notation  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Blind Signature Protocol Overview . . . . . . . . . . . . . .   4
   5.  RSABSSA Signature Instantiation . . . . . . . . . . . . . . .   4
     5.1.  Signature Generation  . . . . . . . . . . . . . . . . . .   4
       5.1.1.  Blind . . . . . . . . . . . . . . . . . . . . . . . .   5
       5.1.2.  BlindSign . . . . . . . . . . . . . . . . . . . . . .   5
       5.1.3.  Finalize  . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  Encoding Options  . . . . . . . . . . . . . . . . . . . .   7
   6.  Public Key Certification  . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
     7.1.  Timing Side Channels  . . . . . . . . . . . . . . . . . .   8
     7.2.  Message Robustness  . . . . . . . . . . . . . . . . . . .   8
     7.3.  Salt State  . . . . . . . . . . . . . . . . . . . . . . .   9
     7.4.  Key Substitution Attacks  . . . . . . . . . . . . . . . .   9
     7.5.  Alternative RSA Encoding Functions  . . . . . . . . . . .   9
     7.6.  Alternative Blind Signature Schemes . . . . . . . . . . .   9
     7.7.  Post-Quantum Readiness  . . . . . . . . . . . . . . . . .  10
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Test Vector  . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Originally introduced in the context of digital cash systems by Chaum
   for untraceable payments [Chaum83], RSA blind signatures turned out
   to have a wide range of applications ranging from electric voting
   schemes to authentication mechanisms.

   Recently, interest in blind signatures has grown to address
   operational shortcomings from VOPRFs such as [I-D.irtf-cfrg-voprf].
   Specifically, VOPRF evaluation requires access to the private key,
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