General Purpose Extended Key Usage (EKU) for Document Signing X.509 Certificates
draft-ito-documentsigning-eku-00

Document Type Active Internet-Draft (individual)
Authors Tadahiko Ito  , Tomofumi Okubo 
Last updated 2021-04-01
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Individual                                                        T. Ito
Internet-Draft                                           SECOM CO., LTD.
Intended status: Informational                                  T. Okubo
Expires: October 3, 2021                                  DigiCert, Inc.
                                                          April 01, 2021

  General Purpose Extended Key Usage (EKU) for Document Signing X.509
                              Certificates
                    draft-ito-documentsigning-eku-00

Abstract

   [RFC5280] specifies several extended key usages for X.509
   certificates.  This document defines a general purpose document
   signing extended key usage for X.509 public key certificates which
   restricts the usage of the certificates for document signing.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 3, 2021.

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Extended Key usage for DocumentSigning  . . . . . . . . . . .   3
     3.1.  Extended Key Usage Values for Document Signing  . . . . .   3
   4.  Implications for a Certification Authority  . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   [RFC5280] specifies several extended key usages for X.509
   certificates.  In addition, several extended key usage had been
   added[RFC7299] as public OID under the IANA repository.  While usage
   of any extended key usage is bad practice for publicly trusted
   certificates, there are no public and general extended key usage
   explicitly assigned for Document Signing certificates.  The current
   practice is to use id-kp-emailProtection, id-kp-codeSigning or vendor
   defined Object ID for general document signing purposes.

   In circumstances where code signing and S/MIME certificates are also
   widely used for document signing, the technical or policy changes
   that are made to code signing and S/MIME certificates may cause
   unexpected behaviors or have an adverse impact such as decreased
   cryptographic agility on the document signing ecosystem and vice
   versa.

   There is no issue if the vendor defined OIDs are used in a PKI (or a
   trust program) governed by the vendor.  However, if the OID is used
   outside of the vendor governance, the usage can easily become out of
   control (e.g. - When the end user encounters vendor defined OIDs,
   they might want to ask that vendor about use of the certificate,
   however, the vendor may not know about the particular use. - If the
   issuance of the cert is not under the control of the OID owner, there
   is no way for the OID owner to know what the impact will be if any
   change is made to the OID in question, and it would restrict vendor's
   choice of OID management. etc.).

   Therefore, it is not favorable to use a vendor defined EKU for
   signing a document that is not governed by the vendor.

   This document defines a general Document Signing extended key usage.

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2.  Conventions and Definitions
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