RFC 9295: Clarifications for Ed25519, Ed448, X25519, and X448 Algorithm Identifiers

Status of This Memo

This is an Internet Standards Track document.¶

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9295.¶

Copyright Notice

Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶

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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 keyUsage extension [RFC5280]. [RFC8410] did not define what values are not permissible, nor did it refer to keyEncipherment or dataEncipherment. [Err5696] 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
  decipherOnly

and any of the following MUST NOT be present:¶

  digitalSignature
  nonRepudiation
  keyEncipherment
  dataEncipherment
  keyCertSign
  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
  cRLSign

and any of the following MUST NOT be present:¶

  keyEncipherment
  dataEncipherment
  keyAgreement
  keyCertSign
  encipherOnly
  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
  digitalSignature

and any of the following MUST NOT be present:¶

  keyEncipherment
  dataEncipherment
  keyAgreement
  encipherOnly
  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
  cRLSign

and any of the following MUST NOT be present:¶

  keyEncipherment
  dataEncipherment
  keyAgreement
  encipherOnly
  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.¶

Acknowledgments

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

Authors' Addresses