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Using EdDSA in the Internet X.509 Public Key Infrastructure
draft-josefsson-pkix-eddsa-01

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Author Simon Josefsson
Last updated 2015-06-15
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draft-josefsson-pkix-eddsa-01
Network Working Group                                       S. Josefsson
Internet-Draft                                                    SJD AB
Intended status: Informational                             June 15, 2015
Expires: December 17, 2015

      Using EdDSA in the Internet X.509 Public Key Infrastructure
                     draft-josefsson-pkix-eddsa-01

Abstract

   This document specify algorithm identifiers and ASN.1 encoding
   formats for EdDSA digital signatures and subject public keys used in
   the Internet X.509 Public Key Infrastructure (PKIX) for Certificates
   and CRLs.  Parameters for Ed25519 are defined.

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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 17, 2015.

Copyright Notice

   Copyright (c) 2015 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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1.  Introduction

   In [Ed25519], an elliptic curve signature system EdDSA was
   introduced, and a recommended choice of curve Ed25519 is chosen.
   EdDSA and Ed25519 was designed with performance and security in mind.
   Specification, test vectors and a sample implementation is available
   in [I-D.josefsson-eddsa-ed25519].

   This RFC defines ASN.1 object identifiers for EdDSA for use in the
   Internet X.509 PKI [RFC5280], and parameters for Ed25519.  This
   document serves a similar role as [RFC3279] does for RSA (and more),
   [RFC4055] for RSA-OAEP/PSS, and [RFC5758] for SHA2-based (EC)DSA.

2.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  EdDSA ASN.1 Object Identifier Tree

   The root of the tree for the object identifiers defined in this
   specification is given by:

       id-EdDSA OBJECT IDENTIFIER ::= { 1.3.6.1.4.1.11591.4.12 }

   [[TODO: Find a shorter OID.  https://gitlab.com/jas/ietf-pkix-eddsa/
   issues/4 ]]

4.  Subject Public Key Information Fields

   In the X.509 certificate, the subjectPublicKeyInfo field has the
   SubjectPublicKeyInfo type, which has the following ASN.1 syntax:

        SubjectPublicKeyInfo  ::=  SEQUENCE  {
          algorithm         AlgorithmIdentifier,
          subjectPublicKey  BIT STRING
        }

   The fields in SubjectPublicKeyInfo have the following meanings:

   o  algorithm is the algorithm identifier and parameters for the
      public key (see below).

   o  subjectPublicKey is the EdDSA public key.

   The AlgorithmIdentifier type, which is included for convenience, is
   defined as follows:

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         AlgorithmIdentifier  ::=  SEQUENCE  {
           algorithm   OBJECT IDENTIFIER,
           parameters  ANY DEFINED BY algorithm OPTIONAL
         }

   The fields in AlgorithmIdentifier have the following meanings:

   o  algorithm identifies the cryptographic algorithm with an object
      identifier.  This is the EdDSA OID defined below.

   o  parameters, which are optional, are the associated parameters for
      the algorithm identifier in the algorithm field.

5.  EdDSA Public Keys

   Certificates conforming to [RFC5280] may convey a public key for any
   public key algorithm.  The certificate indicates the algorithm
   through an algorithm identifier.  This algorithm identifier is an OID
   and optionally associated parameters.

   This section identify the OID and parameters for the EdDSA algorithm.
   Conforming CAs MUST use the identified OIDs when issuing certificates
   containing EdDSA public keys.  Conforming applications supporting
   EdDSA MUST, at a minimum, recognize the OID identified in this
   section.

   The id-EdDSAPublicKey OID is used for identifying EdDSA public keys.

          id-EdDSAPublicKey OBJECT IDENTIFIER ::= { id-EdDSA 1 }

   The id-EdDSAPublicKey OID is intended to be used in the algorithm
   field of a value of type AlgorithmIdentifier.

   EdDSA public keys use the parameter field to specify the particular
   instantiation of EdDSA parameters.  The parameters field have the
   ASN.1 type EdDSAParameters as follows.

       EdDSAParameters ::= ENUMERATED { ed25519 (1) }

   The EdDSAParameters enumeration may be extended in the future.

   The raw binary EdDSA public key is encoded directly in the
   subjectPublicKey BIT STRING object.

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6.  Key Usage Bits

   The intended application for the key MAY be indicated in the keyUsage
   certificate extension.

   If the keyUsage extension is present in an end-entity certificate
   that conveys an EdDSA public key with the id-EdDSAPublicKey object
   identifier, then the keyUsage extension MUST contain one or both of
   the following values:

          nonRepudiation; and
          digitalSignature.

   If the keyUsage extension is present in a certification authority
   certificate that conveys an EdDSA public key with the id-
   EdDSAPublicKey object identifier, then the keyUsage extension MUST
   contain one or more of the following values:

          nonRepudiation;
          digitalSignature;
          keyCertSign; and
          cRLSign.

7.  EdDSA Signatures

   Certificates and CRLs conforming to [RFC5280] may be signed with any
   public key signature algorithm.  The certificate or CRL indicates the
   algorithm through an algorithm identifier which appears in the
   signatureAlgorithm field within the Certificate or CertificateList.
   This algorithm identifier is an OID and has optionally associated
   parameters.  For illustration the Certificate structure is reproduced
   here:

      Certificate  ::=  SEQUENCE  {
           tbsCertificate       TBSCertificate,
           signatureAlgorithm   AlgorithmIdentifier,
           signatureValue       BIT STRING  }

   Recall the definition of the AlgorithmIdentifier type:

         AlgorithmIdentifier  ::=  SEQUENCE  {
           algorithm   OBJECT IDENTIFIER,
           parameters  ANY DEFINED BY algorithm OPTIONAL
         }

   This document identify an AlgorithmIdentifier OID for EdDSA
   signatures.  No parameters are defined.  The EdDSA parameters follow
   from the public-key parameters.

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   The data to be signed is prepared for EdDSA.  Then, a private key
   operation is performed to generate the signature value.  This
   signature value is then ASN.1 encoded as a BIT STRING and included in
   the Certificate or CertificateList in the signatureValue field.

   The id-EdDSASignature OID is used for identifying EdDSA signatures.

          id-EdDSASignature OBJECT IDENTIFIER ::= { id-EdDSA 2 }

   The id-EdDSASignature OID is intended to be used in the algorithm
   field of a value of type AlgorithmIdentifier.  The parameters field
   MUST be absent.  To further clarify how to encode the parameters
   field, due to historical misunderstandings in this area, it MUST NOT
   have an ASN.1 type NULL.

8.  Examples

   An example of a X.509v1 certificate using EdDSA would be:

-----BEGIN CERTIFICATE-----
MIHpMIGTAgIAgDAOBgorBgEEAdpHBAwCBQAwEjEQMA4GA1UEAxMHRXhhbXBsZTAeFw0xNTA2MDgx
NDEzMTNaFw0xNTA5MDgxNDEzMTNaMBIxEDAOBgNVBAMTB0V4YW1wbGUwNTAOBgorBgEEAdpHBAwB
BQADIwAEIOWj2mfLDCaC9FMMddwIg9WxktAcusgNUUUSVaa2pNlAMA4GCisGAQQB2kcEDAIFAANB
AAZCIvRcw03Utgmf8Xmgx0lQbp5XBzDG3xNquT2urGD+GMfbJSAGmx/dDoDre1ZctxG2XLZ249ly
fGTaTn5Fiw8=
-----END CERTIFICATE-----

   An example of a raw Ed25519 public key certificate:

MDUwDgYKKwYBBAHaRwQMAQUAAyMABCAu4FI+ME5I7qtL2Kh0nJryEqLjrM0kh4yJwU1QUYEdQg==

9.  Acknowledgements

   Text and/or inspiration were drawn from [RFC5280], [RFC3279],
   [RFC4055], [RFC5480], and [RFC5639].

   Thanks to Klaus Hartke and Ilari Liusvaara for fixes, ideas and
   discussion.

10.  IANA Considerations

   None.

11.  Security Considerations

   The security considerations of [RFC5280] and
   [I-D.josefsson-eddsa-ed25519] apply accordingly.

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12.  References

12.1.  Normative References

   [I-D.josefsson-eddsa-ed25519]
              Josefsson, S. and N. Moller, "EdDSA and Ed25519", draft-
              josefsson-eddsa-ed25519-02 (work in progress), February
              2015.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

12.2.  Informative References

   [RFC3279]  Bassham, L., Polk, W., and R. Housley, "Algorithms and
              Identifiers for the Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 3279, April 2002.

   [RFC4055]  Schaad, J., Kaliski, B., and R. Housley, "Additional
              Algorithms and Identifiers for RSA Cryptography for use in
              the Internet X.509 Public Key Infrastructure Certificate
              and Certificate Revocation List (CRL) Profile", RFC 4055,
              June 2005.

   [RFC5480]  Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
              "Elliptic Curve Cryptography Subject Public Key
              Information", RFC 5480, March 2009.

   [RFC5639]  Lochter, M. and J. Merkle, "Elliptic Curve Cryptography
              (ECC) Brainpool Standard Curves and Curve Generation", RFC
              5639, March 2010.

   [RFC5758]  Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T.
              Polk, "Internet X.509 Public Key Infrastructure:
              Additional Algorithms and Identifiers for DSA and ECDSA",
              RFC 5758, January 2010.

   [Ed25519]  Bernstein, J., Duif, , Lange, , Schwabe, , and Yang,
              "Ed25519: High-speed high-security signatures", WWW
              http://ed25519.cr.yp.to/ed25519-20110926.pdf, September
              2011.

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Author's Address

   Simon Josefsson
   SJD AB

   Email: simon@josefsson.org

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