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Network Working Group                                          J. Schaad
Internet-Draft                                            August Cellars
Intended status: Informational                           4 December 2019
Expires: 6 June 2020


  Cryptographic Message System (CMS) Content Types for Concise Binary
                      Object Representation (CBOR)
                      draft-schaad-cbor-content-02

Abstract

   Concise Binary Object Representation (CBOR) is becoming a widely used
   method of doing content encoding.  Cryptographic Message System (CMS)
   is still a widely used method of doing message-based security.  This
   document defines a set of content types for CMS that hold CBOR
   content.

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 6 June 2020.

Copyright Notice

   Copyright (c) 2019 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
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   provided without warranty as described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  CBOR Content Type . . . . . . . . . . . . . . . . . . . . . .   2
   3.  CBOR Sequence Content Type  . . . . . . . . . . . . . . . . .   3
   4.  ASN.1 Module  . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Concise Binary Object Representation (CBOR) [CBOR] is a compact self-
   describing binary encoding formation that is starting to be used in
   many different applications.  One of the primary uses of CBOR is in
   the Internet of Things where the constrained nature means that having
   minimal size of encodings becomes very important.  The use of the
   Cryptographic Message System (CMS) [CMS] is still one of the most
   common method for providing message-based security, although in many
   cases the CBOR Object Signing and Encryption (COSE) [COSE] message-
   based security system is starting to be used.  Given that CBOR is
   going to be transported using CMS, it makes sense to define CMS
   content types for the purpose of denoting that the embedded content
   is CBOR.  This document defines two new content types: CBOR Content
   Type and CBOR Sequence Content Type [CBOR-SEQ].

2.  CBOR Content Type

   [CBOR] defines an encoded CBOR item.  This section defines a new
   content type for wrapping an encoded CBOR item in a CMS object.

   The following object identifier identifies the CBOR content type:

   id-ct-cbor OBJECT IDENTIFIER ::= { iso(1) member-body(2) usa(840)
           rsadsi(113549) pkcs(1) pkcs9(9) smime(16) ct(1) TBD1 }

   The CBOR content type is intended to refer to a single object encoded
   using the CBOR encoding format [CBOR].  Nothing is stated about the
   specific CBOR object that is included.  CBOR can always be decoded to
   a tree as the encoding is self descriptive.

   The CBOR content type is intended to be encapsulated in the signed
   data and auth-enveloped data, but can be included in any CMS wrapper.
   It cannot be predicted if the compressed CMS encapsulation will
   provide compression as the content may be binary rather than text.





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   [RFC7193] defined an optional parameter "innerContent" to allow for
   identification of what the inner content is for an application/cms
   media type.  This document defines the string "cbor" as a new value
   that can be placed here when a CBOR content type is used.

3.  CBOR Sequence Content Type

   [CBOR-SEQ] defines a CBOR Sequence as a concatenation of zero or more
   CBOR objects.  This section defines a new content type for wrapping a
   CBOR Sequence in a CMS object.

   The following object identifier identifies the CBOR Sequence content
   type:

   id-ct-cborSequence OBJECT IDENTIFIER ::= { iso(1) member-body(2)
           usa(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) ct(1)
           TBD2 }

   The CBOR Sequence content type is intended to refer to a sequence of
   objects encoded using the CBOR encoding format.  The objects are
   concatenated without any markers delimiting the individual CBOR
   objects.  Nothing is stated about the specific CBOR objects that are
   included.  CBOR can always be decoded to a tree as the encoding is
   self descriptive.

   The CBOR Sequence content type is intended to be encapsulated in the
   signed data and auth-enveloped data, but can be included in any CMS
   wrapper.  It cannot be predicted if the compressed CMS encapsulation
   will provide compression as the content may be binary rather than
   text.

   [RFC7193] defined an optional parameter "innerContent" to allow for
   identification of what the inner content is for an application/cms
   media type.  This document defines the string "cborSequence" as a new
   value that can be placed here when a CBOR Sequence content type is
   used.

4.  ASN.1 Module













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   CborContentTypes { iso(1) member-body(2) usa(840)
           rsadsi(113549) pkcs(1) pkcs9(9) smime(16) modules(0)
           id-mod-cbor-2019(TBD3) }
   DEFINITIONS EXPLICIT TAGS ::=
   BEGIN
   IMPORTS

       CONTENT-TYPE
       FROM  CryptographicMessageSyntax-2010
         { iso(1) member-body(2) us(840) rsadsi(113549)
            pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) }
       ;

       id-ct-cbor OBJECT IDENTIFIER ::= { iso(1) member-body(2)
           us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) ct(1)
           TBD1 }

       id-ct-cborSequence OBJECT IDENTIFIER ::= { iso(1) member-body(2)
           us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) ct(1)
           TBD2 }

       -- Content is encoded directly and does not have any ASN.1
       --    structure
       ct-Cbor CONTENT-TYPE ::= { IDENTIFIED BY id-ct-cbor }

       -- Content is encoded directly and does not have any ASN.1
       --    structure
       ct-CborSequence CONTENT-TYPE ::= {
           IDENTIFIED BY id-ct-cborSequence
       }

   END

5.  IANA Considerations

   In the "SMI Security for S/MIME Module Identifier" registry, create a
   new entry to point to this document.

            +---------+------------------+-------------------+
            | Decimal | Description      | References        |
            +=========+==================+===================+
            | TBD3    | id-mod-cbor-2019 | [[This Document]] |
            +---------+------------------+-------------------+

                                 Table 1

   In the "SMI Security for S/MIME Content Types" registry, add two new




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   entries for id-ct-cbor and id-ct-cborSequence that point to this
   document.

           +---------+--------------------+-------------------+
           | Decimal | Description        | References        |
           +=========+====================+===================+
           | TBD1    | id-ct-cbor         | [[This Document]] |
           +---------+--------------------+-------------------+
           | TBD2    | id-ct-cborSequence | [[This Document]] |
           +---------+--------------------+-------------------+

                                 Table 2

   In the table "CMS Inner Content Types" add two new entries:

    +--------------+------------------------------+-------------------+
    | Name         | Object Identifier            | Reference         |
    +==============+==============================+===================+
    | cbor         | 1.2.840.113549.1.9.16.1.TBD1 | [[This Document]] |
    +--------------+------------------------------+-------------------+
    | cborSequence | 1.2.840.113549.1.9.16.1.TBD2 | [[This Document]] |
    +--------------+------------------------------+-------------------+

                                  Table 3

6.  Security Considerations

   This document only provides identification for content types, it does
   not introduce any new security issues by itself.  The new content
   types mean that id-data does not need to be used to identify these
   content types and thus can reduce confusion.

7.  Normative References

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

   [CBOR]     Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [COSE]     Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,
              <https://www.rfc-editor.org/info/rfc8152>.

   [RFC7193]  Turner, S., Housley, R., and J. Schaad, "The application/




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              cms Media Type", RFC 7193, DOI 10.17487/RFC7193, April
              2014, <https://www.rfc-editor.org/info/rfc7193>.

   [CBOR-SEQ] Bormann, C., "Concise Binary Object Representation (CBOR)
              Sequences", Work in Progress, Internet-Draft, draft-ietf-
              cbor-sequence-02, 25 September 2019,
              <https://tools.ietf.org/html/draft-ietf-cbor-sequence-02>.

Author's Address

   Jim Schaad
   August Cellars

   Email: ietf@augustcellars.com





































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