Clarifications for Ed25519, Ed448, X25519, and X448 Algorithm Identifiers
draft-ietf-lamps-8410-ku-clarifications-02

LAMPS                                                          S. Turner
Internet-Draft                                                     sn3rd
Updates: 8410 (if approved)                                 S. Josefsson
Intended status: Standards Track                                  SJD AB
Expires: 1 January 2023                                      D. McCarney
                                                             Square Inc.
                                                                  T. Ito
                                                         SECOM CO., LTD.
                                                            30 June 2022

     Clarifications for Ed25519, Ed448, X25519, and X448 Algorithm
                              Identifiers
               draft-ietf-lamps-8410-ku-clarifications-02

Abstract

   This document updates RFC 8410 to clarify existing and specify
   missing semantics for key usage bits when used in certificates that
   support the Ed25519, Ed448, X25519, and X448 Elliptic Curve
   Cryptography algorithms.

About This Document

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

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-lamps-8410-ku-
   clarifications/.

   Source for this draft and an issue tracker can be found at
   https://github.com/lamps-wg/8410-ku-clarifications.

Status of This Memo

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

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Copyright Notice

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   document authors.  All rights reserved.

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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  New Section 5 for RFC 8410  . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   [RFC8410] specifies the syntax and semantics for the Subject Public
   Key Information field in certificates that support Ed25519, Ed448,
   X25519, and X448 Elliptic Curve Cryptography (ECC) algorithms.  As
   part of these semantics, it defines what combinations are permissible
   for the values of the key usage extension [RFC5280].  [RFC8410] did
   not define what values are not permissible nor did it refer to
   keyEncipherment or dataEncipherment.  [ERRATA] has also been
   submitted to clarify that keyCertSign is always set in certification
   authority certificates.  To address these changes, this document
   replaces Section 5 of [RFC8410] with Section 3.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  New Section 5 for RFC 8410

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

   If the keyUsage extension is present in a certificate that indicates
   id-X25519 or id-X448 in SubjectPublicKeyInfo, then the following MUST
   be present:

     keyAgreement;

   one of the following MAY also be present:

     encipherOnly; or
     decipherOnly;

   and the following MUST NOT be present:

     digitalSignature;
     nonRepudiation;
     keyEncipherment;
     dataEncipherment;
     keyCertSign; and
     cRLSign.

   If the keyUsage extension is present in an end-entity certificate
   that indicates id-Ed25519 or id-Ed448 in SubjectPublicKeyInfo, then
   the keyUsage extension MUST contain at least one of the following:

     nonRepudiation;
     digitalSignature; and
     cRLSign;

   and the following MUST NOT be present:

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     keyEncipherment;
     dataEncipherment;
     keyAgreement;
     keyCertSign;
     encipherOnly; and
     decipherOnly.

   If the keyUsage extension is present in a CRL issuer certificate that
   indicates id-Ed25519 or id-Ed448 in SubjectPublicKeyInfo, then the
   keyUsage extension MUST contain:

   ~~ cRLSign; ~~

   and zero or more of the following:

   ~~ nonRepudiation; and digitalSignature; ~~

   and the following MUST NOT be present:

   ~~ keyEncipherment; dataEncipherment; keyAgreement; encipherOnly; and
   decipherOnly; ~~

   and if the CRL issuer is also a certification authority, then the
   keyUsage extension MUST also contain:

   ~~ keyCertSign. ~~

   If the keyUsage extension is present in a certification authority
   certificate that indicates id-Ed25519 or id-Ed448 in
   SubjectPublicKeyInfo, then the keyUsage extension MUST contain:

     keyCertSign

   and zero or more of the following:

     nonRepudiation;
     digitalSignature; and
     cRLSign;

   and the following MUST NOT be present:

     keyEncipherment;
     dataEncipherment;
     keyAgreement;
     encipherOnly; and
     decipherOnly.

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4.  Security Considerations

   This document introduces no new security considerations beyond those
   found in [RFC8410].

5.  IANA Considerations

   This document has no IANA actions.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [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, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/rfc/rfc5280>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8410]  Josefsson, S. and J. Schaad, "Algorithm Identifiers for
              Ed25519, Ed448, X25519, and X448 for Use in the Internet
              X.509 Public Key Infrastructure", RFC 8410,
              DOI 10.17487/RFC8410, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8410>.

6.2.  Informative References

   [ERRATA]   Liao, L., "Errata 5696", 17 April 2019,
              <https://www.rfc-editor.org/errata/eid5696>.

Acknowledgments

   We would like to thank Russ Housley, Mike Jenkins, and Corey Bonnell
   for the comments.

Authors' Addresses

   Sean Turner
   sn3rd

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   Email: sean@sn3rd.com

   Simon Josefsson
   SJD AB
   Email: simon@josefsson.org

   Daniel McCarney
   Square Inc.
   Email: daniel@binaryparadox.net

   Tadahiko Ito
   SECOM CO., LTD.
   Email: tadahiko.ito.public@gmail.com

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