RFC 8410: Algorithm Identifiers for Ed25519, Ed448, X25519, and X448 for Use in the Internet X.509 Public Key Infrastructure | RFC Editor

Skip to content Primary navigationThe RFC SeriesFor AuthorsAbout UsHomeRFC 8410 View as: Plain Text, Compact HTML Info RFC 8410: Algorithm Identifiers for Ed25519, Ed448, X25519, and X448 for Use in the Internet X.509 Public Key InfrastructureCurve25519EdDSAASN.1X.509August 2018. S. Josefsson, J. SchaadProposed StandardSubscribe8 subscribed Add to Set Added to 1 Set Read aloud This RFC was updated, see RFC 9295.Internet Engineering Task Force (IETF) S. Josefsson Request for Comments: 8410 SJD AB Category: Standards Track J. Schaad ISSN: 2070-1721 August Cellars August 2018 Algorithm Identifiers for Ed25519, Ed448, X25519, and X448 for Use in the Internet X.509 Public Key Infrastructure Abstract This document specifies algorithm identifiers and ASN.1 encoding formats for elliptic curve constructs using the curve25519 and curve448 curves. The signature algorithms covered are Ed25519 and Ed448. The key agreement algorithms covered are X25519 and X448. The encoding for public key, private key, and Edwards-curve Digital Signature Algorithm (EdDSA) structures is provided. 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/rfc8410. Copyright Notice Copyright (c) 2018 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Josefsson & Schaad Standards Track [Page 1] RFC 8410 Safe Curves for X.509 August 2018 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Terminology . . . . . . . . . . . . . . . . . . 3 3. Curve25519 and Curve448 Algorithm Identifiers . . . . . . . . 3 4. Subject Public Key Fields . . . . . . . . . . . . . . . . . . 4 5. Key Usage Bits . . . . . . . . . . . . . . . . . . . . . . . 5 6. EdDSA Signatures . . . . . . . . . . . . . . . . . . . . . . 6 7. Private Key Format . . . . . . . . . . . . . . . . . . . . . 7 8. Human-Readable Algorithm Names . . . . . . . . . . . . . . . 8 9. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . 9 10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 10.1. Example Ed25519 Public Key . . . . . . . . . . . . . . . 11 10.2. Example X25519 Certificate . . . . . . . . . . . . . . . 12 10.3. Examples of Ed25519 Private Key . . . . . . . . . . . . 14 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 12. Security Considerations . . . . . . . . . . . . . . . . . . . 15 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 13.1. Normative References . . . . . . . . . . . . . . . . . . 16 13.2. Informative References . . . . . . . . . . . . . . . . . 16 Appendix A. Invalid Encodings . . . . . . . . . . . . . . . . . 18 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 1. Introduction In [RFC7748], the elliptic curves curve25519 and curve448 are described. They are designed with performance and security in mind. The curves may be used for Diffie-Hellman and digital signature operations. [RFC7748] describes the operations on these curves for the Diffie- Hellman operation. A convention has developed that when these two curves are used with the Diffie-Hellman operation, they are referred to as X25519 and X448. This RFC defines the ASN.1 Object Identifiers (OIDs) for the operations X25519 and X448 along with the associated parameters. The use of these OIDs is described for public and private keys. In [RFC8032] the elliptic curve signature system Edwards-curve Digital Signature Algorithm (EdDSA) is described along with a recommendation for the use of the curve25519 and curve448. EdDSA has defined two modes: the PureEdDSA mode without prehashing and the HashEdDSA mode with prehashing. The convention used for identifying the algorithm/curve combinations is to use "Ed25519" and "Ed448" for the PureEdDSA mode. This document does not provide the conventions Josefsson & Schaad Standards Track [Page 2] RFC 8410 Safe Curves for X.509 August 2018 needed for the prehash versions of the signature algorithm. The use of the OIDs is described for public keys, private keys and signatures. [RFC8032] additionally defines the concept of a context. Contexts can be used to differentiate signatures generated for different purposes with the same key. The use of contexts is not defined in this document for the following reasons: o The current implementations of Ed25519 do not support the use of contexts; thus, if specified, it will potentially delay the use of these algorithms further. o EdDSA is the only IETF algorithm that currently supports the use of contexts; however, there is a possibility that there will be confusion between which algorithms need to have separate keys and which do not. This may result in a decrease of security for those other algorithms. o There are still ongoing discussions among the cryptographic community about how effective the use of contexts is for preventing attacks. o There needs to be discussions about the correct way to id