PKCS #8 Private-Key Information Content Types
draft-ietf-lamps-pkcs8-prikeyinfo-contenttypes-04

Limited Additional Mechanisms for PKIX and SMIME               J. Mandel
Internet-Draft                                                    AKAYLA
Intended status: Standards Track                              R. Housley
Expires: 6 April 2026                                     Vigil Security
                                                               S. Turner
                                                                   sn3rd
                                                          3 October 2025

             PKCS #8 Private-Key Information Content Types
           draft-ietf-lamps-pkcs8-prikeyinfo-contenttypes-04

Abstract

   This document defines PKCS #8 content types for use with
   PrivateKeyInfo and EncryptedPrivateKeyInfo as specified in RFC 5958.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at https://github.com/
   lamps-wg/pkcs8-PriKeyInfoCt.  Status information for this document
   may be found at https://datatracker.ietf.org/doc/draft-ietf-lamps-
   pkcs8-prikeyinfo-contenttypes/.

   Discussion of this document takes place on the Limited Additional
   Mechanisms for PKIX and SMIME mailing list (mailto:spasm@ietf.org),
   which is archived at https://mailarchive.ietf.org/arch/browse/spasm/.
   Subscribe at https://www.ietf.org/mailman/listinfo/spasm/.

   Source for this draft and an issue tracker can be found at
   https://github.com/lamps-wg/pkcs8-PriKeyInfoCt.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

Mandel, et al.            Expires 6 April 2026                  [Page 1]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

   This Internet-Draft will expire on 6 April 2026.

Copyright Notice

   Copyright (c) 2025 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
   2.  Private-Key Information Content Types . . . . . . . . . . . .   2
   3.  ASN.1 Module  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The syntax for private-key information was originally described in
   [RFC5208], and the syntax was later revised by [RFC5958] to include
   the AsymmetricKeyPackage content type that supports multiple
   PrivateKeyInfos.  This document defines PKCS #8 content types for use
   with one PrivateKeyInfo and EncryptedPrivateKeyInfo.  These content
   type assignments are needed for PrivateKeyInfo and
   EncryptedPrivateKeyInfo to be carried in the Cryptographic Message
   Syntax (CMS) [RFC5652].

   Note: A very long time ago, media types for PrivateKeyInfo and
   EncryptedPrivateKeyInfo were assigned as application/pkcs8 and
   application/pkcs8-encrypted, respectively.

2.  Private-Key Information Content Types

   This section defines a content type for private-key information and
   encrypted private-key information.

Mandel, et al.            Expires 6 April 2026                  [Page 2]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

   The PrivateKeyInfo content type is identified by the following object
   identifier:

   id-ct-privateKeyInfo OBJECT IDENTIFIER ::= { iso(1)
    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) ct(1) TBD1 }

   The EncryptedPrivateKeyInfo content type is identified by the
   following object identifier:

   id-ct-encrPrivateKeyInfo OBJECT IDENTIFIER ::= { iso(1)
    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) ct(1) TBD2 }

3.  ASN.1 Module

   The ASN.1 module [X680][X690] in this section builds upon the modules
   in [RFC5911].

Mandel, et al.            Expires 6 April 2026                  [Page 3]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

   <CODE BEGINS>
   PrivateKeyInfoContentTypes
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
      pkcs-9(9) smime(16) modules(0) id-mod-pkcs8ContentType(TBD0) }

   DEFINITIONS IMPLICIT TAGS ::=
   BEGIN

   -- EXPORTS ALL

   IMPORTS

   CONTENT-TYPE
    FROM CryptographicMessageSyntax-2009 -- in [RFC5911]
      { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
        pkcs-9(9) smime(16) modules(0) id-mod-cms-2004-02(41) }

   PrivateKeyInfo, EncryptedPrivateKeyInfo
    FROM AsymmetricKeyPackageModuleV1 -- in [RFC5958]
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
         pkcs-9(9) smime(16) modules(0)
         id-mod-asymmetricKeyPkgV1(50) }  ;

   PrivateKeyInfoContentTypes CONTENT-TYPE ::= {
    ct-privateKeyInfo | ct-encrPrivateKeyInfo,
    ... -- Expect additional content types --  }

   ct-privateKeyInfo CONTENT-TYPE ::= { PrivateKeyInfo
    IDENTIFIED BY id-ct-privateKeyInfo }

   id-ct-privateKeyInfo OBJECT IDENTIFIER ::= { iso(1)
    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) ct(1) TBD1 }

   ct-encrPrivateKeyInfo CONTENT-TYPE ::= { EncryptedPrivateKeyInfo
    IDENTIFIED BY id-ct-encrPrivateKeyInfo }

   id-ct-encrPrivateKeyInfo OBJECT IDENTIFIER ::= { iso(1)
    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) ct(1) TBD2 }

   END
   <CODE ENDS>

Mandel, et al.            Expires 6 April 2026                  [Page 4]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

4.  Security Considerations

   The security considerations in [RFC5958] apply here.

5.  IANA Considerations

   For the private key info content types defined in section Section 2,
   IANA is requested to assign an object identifier (OID) for each of
   the content types.  The OIDs for the content types should be
   alloacted in the "SMI Security for S/MIME CMS Content Type" registry
   (1.2.840.113549.1.9.16.1) [IANA-CMS-CTS], and the description should
   be set to id-ct-privateKeyInfo (TDB1) and id-ct-encrPrivateKeyInfo
   (TBD2).

   For the ASN.1 Module in Section 3, IANA is requested to assign an
   object identifier (OID) for the module identifier.  The OID for the
   module should be allocated in the "SMI Security for S/MIME Module
   Identifier" registry (1.2.840.113549.1.9.16.0) [IANA-SMIME-MODS], and
   the Description for the new OID should be set to "id-mod-
   pkcs8ContentType".

   IANA is also requested to update the application/cms entry in the
   "Media Types" registry to add [ RFC-to-be] to the list of RFCs where
   Inner Content Types (ICTs) are defined in the "Optional parameters"
   and the "Interoperability considerations" sections.

   IANA is also requested to update the application/cms entry in the
   "Media Types" registry to add the following values to the
   "innerContent" list:

   *  privateKeyInfo

   *  encrPrivateKeyInfo

   And, to update the following row in the application/cms entry's
   "Security considerations" section:

      +===============+============================================+
      | RFC           | CMS Protecting Content Type and Algorithms |
      +===============+============================================+
      | [ RFC-to-be ] | privateKeyInfo and encrPrivateKeyInfo      |
      +---------------+--------------------------------------------+

                                 Table 1

6.  References

6.1.  Normative References

Mandel, et al.            Expires 6 April 2026                  [Page 5]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/rfc/rfc5652>.

   [RFC5911]  Hoffman, P. and J. Schaad, "New ASN.1 Modules for
              Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
              DOI 10.17487/RFC5911, June 2010,
              <https://www.rfc-editor.org/rfc/rfc5911>.

   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958,
              DOI 10.17487/RFC5958, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5958>.

   [X680]     ITU-T, "Information technology -- Abstract Syntax Notation
              One (ASN.1): Specification of basic notation", ITU-T
              Recommendation X.680, ISO/IEC 8824-1:2021, February 2021,
              <https://www.itu.int/rec/T-REC-X.680>.

   [X690]     ITU-T, "Information technology -- ASN.1 encoding rules:
              Specification of Basic Encoding Rules (BER), Canonical
              Encoding Rules (CER) and Distinguished Encoding Rules
              (DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1-2021,
              February 2021, <https://www.itu.int/rec/T-REC-X.690>.

6.2.  Informative References

   [IANA-CMS-CTS]
              "SMI Security for S/MIME CMS Content Type", n.d.,
              <https://www.iana.org/assignments/smi-numbers/smi-
              numbers.xhtml#security-smime-1>.

   [IANA-SMIME-MODS]
              "SMI Security for S/MIME Module Identifier", n.d.,
              <https://www.iana.org/assignments/smi-numbers/smi-
              numbers.xhtml#security-smime-0>.

   [RFC5208]  Kaliski, B., "Public-Key Cryptography Standards (PKCS) #8:
              Private-Key Information Syntax Specification Version 1.2",
              RFC 5208, DOI 10.17487/RFC5208, May 2008,
              <https://www.rfc-editor.org/rfc/rfc5208>.

Acknowledgments

   Thanks to John Gray, Deb Cooley, Mohamed Boucadair, Orie Steele, and
   Éric Vyncke for reviewing the document and providing comments.

Authors' Addresses

Mandel, et al.            Expires 6 April 2026                  [Page 6]
Internet-Draft    PKCS #8 PrivateKeyInfo Content Types      October 2025

   Joe Mandel
   AKAYLA, Inc.
   Email: joe@akayla.com

   Russ Housley
   Vigil Security, LLC
   Email: housley@vigilsec.com

   Sean Turner
   sn3rd
   Email: sean@sn3rd.com

Mandel, et al.            Expires 6 April 2026                  [Page 7]