RFC 9295

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

Okay bestie, here's the deal. This doc is from the IETF (Internet Engineering Task Force) and it's a Standards Track document, so it's officially part of the Internet's rulebook 💅 It was published in September 2022 (ISSN 2070-1721) and it updates RFC 8410. It doesn't obsolete anything.

The authors are:

• Sean Turner (sn3rd) 🦋
• Simon Josefsson (SJD AB) 🌸
• Daniel McCarney (Square Inc.) 💜
• Tadahiko Ito (SECOM CO., LTD.) 🧚

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Abstract ✨

So the vibe is that this doc updates RFC 8410 to clarify what already exists and fill in the stuff that was missing. The topic is key usage bits in certificates that use the Ed25519, Ed448, X25519, and X448 Elliptic Curve Cryptography algorithms. It's giving clean-up arc 🧹

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.

Info about the current status of this doc, any errata, and how to send feedback lives at https://www.rfc-editor.org/info/rfc9295. Go check it out 👀

Copyright Notice 💖

Copyright (c) 2022 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.

Table of Contents 🍓

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

Acknowledgments

Authors' Addresses

1. Introduction 🫶

Okay so, [RFC8410] lays out the syntax and semantics for the Subject Public Key Information field in certificates that support the Ed25519, Ed448, X25519, and X448 Elliptic Curve Cryptography (ECC) algorithms. Part of those semantics is which combos of values are allowed for the keyUsage extension [RFC5280]. The thing is, [RFC8410] never said which values are NOT allowed, and it also didn't mention keyEncipherment or dataEncipherment. Plus, [Err5696] was submitted to clarify that keyCertSign is always set in certification authority certificates. 😭 To fix all of this, this doc replaces Section 5 of [RFC8410] with Section 3. Main character glow-up energy ✨

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. Literally the whole point 🙈

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]. Phew, so the security stuff is already covered there, no drama 😌

5. IANA Considerations 🧚

This document has no IANA actions. Nothing to register, bestie ✨

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/info/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/info/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/info/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/info/rfc8410>.

6.2. Informative References

[Err5696] RFC Errata, Erratum ID 5696, RFC 8410, <https://www.rfc-editor.org/errata/eid5696>.

Acknowledgments 🫶

We would like to thank Russ Housley, Mike Jenkins, and Corey Bonnell for their comments. Shoutout to the reviewers, you're iconic 👑

Authors' Addresses 🎀

Sean Turner sn3rd 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