Elliptic Curve-Based Certificateless Signatures for Identity-Based Encryption (ECCSI)
RFC 6507

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Internet Engineering Task Force (IETF)                         M. Groves
Request for Comments: 6507                                          CESG
Category: Informational                                    February 2012
ISSN: 2070-1721

            Elliptic Curve-Based Certificateless Signatures
                 for Identity-Based Encryption (ECCSI)

Abstract

   Many signature schemes currently in use rely on certificates for
   authentication of identity.  In Identity-based cryptography, this
   adds unnecessary overhead and administration.  The Elliptic Curve-
   based Certificateless Signatures for Identity-based Encryption
   (ECCSI) signature scheme described in this document is
   certificateless.  This scheme has the additional advantages of low
   bandwidth and low computational requirements.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It has been approved for publication by the Internet
   Engineering Steering Group (IESG).  Not all documents approved by the
   IESG are a candidate for any level of Internet Standard; see Section
   2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6507.

Copyright Notice

   Copyright (c) 2012 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
   Provisions Relating to IETF Documents
   (http://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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Groves                        Informational                     [Page 1]
RFC 6507           ECCSI for Identity-Based Encryption     February 2012

Table of Contents

   1. Introduction ....................................................2
      1.1. Requirements Terminology ...................................3
   2. Architecture ....................................................3
   3. Notation ........................................................5
      3.1. Arithmetic .................................................5
      3.2. Representations ............................................6
      3.3. Format of Material .........................................6
   4. Parameters ......................................................7
      4.1. Static Parameters ..........................................7
      4.2. Community Parameters .......................................8
   5. Algorithms ......................................................8
      5.1. User Key Material ..........................................8
           5.1.1. Algorithm for Constructing (SSK,PVT) Pair ...........8
           5.1.2. Algorithm for Validating a Received SSK .............9
      5.2. Signatures .................................................9
           5.2.1. Algorithm for Signing ...............................9
           5.2.2. Algorithm for Verifying ............................10
   6. Security Considerations ........................................11
   7. References .....................................................13
      7.1. Normative References ......................................13
      7.2. Informative References ....................................13
   Appendix A. Test Data..............................................14

1.  Introduction

   Digital signatures provide authentication services across a wide
   range of applications.  A chain of trust for such signatures is
   usually provided by certificates.  However, in low-bandwidth or other
   resource-constrained environments, the use of certificates might be
   undesirable.  This document describes an efficient scheme, ECCSI, for
   elliptic curve-based certificateless signatures, primarily intended
   for use with Identity-Based Encryption (IBE) schemes such as
   described in [RFC6508].  As certificates are not needed, the need to
   transmit or store them to authenticate each communication is
   obviated.  The algorithm has been developed by drawing on ideas set
   out by Arazi [BA] and is originally based upon the Elliptic Curve
   Digital Signature Algorithm [ECDSA], one of the most commonly used
   signature algorithms.

   The algorithm is for use in the following context:

      *  where there are two parties, a Signer and a Verifier;

      *  where short unambiguous Identifier strings are naturally
         associated to each of these parties;