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

Document Type RFC - Proposed Standard (August 2018; Errata)
Last updated 2018-08-14
Replaces draft-ietf-curdle-pkix-newcurves, draft-ietf-curdle-pkix-eddsa
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Document shepherd Daniel Migault
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Send notices to "Daniel Migault" <daniel.migault@ericsson.com>
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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
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