Internet-Draft curve25519, curve448 ECC Clarifications April 2022
Turner, et al. Expires 3 October 2022 [Page]
Workgroup:
LAMPS
Internet-Draft:
draft-ietf-lamps-8410-ku-clarifications-01
Updates:
8410 (if approved)
Published:
Intended Status:
Standards Track
Expires:
Authors:
S. Turner
sn3rd
S. Josefsson
SJD AB
D. McCarney
Square Inc.
T. Ito
SECOM CO., LTD.

Clarifications for Ed25519, Ed448, X25519, and X448 Algorithm Identifiers

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.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 3 October 2022.

Table of Contents

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.

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 or CRL issuer 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:

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

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.

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, , <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, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc8410>.

6.2. Informative References

[ERRATA]
Liao, L., "Errata 5696", , <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
Simon Josefsson
SJD AB
Daniel McCarney
Square Inc.
Tadahiko Ito
SECOM CO., LTD.

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