Network Working Group                                          J. Schaad
Internet-Draft                                            August Cellars
Intended status: Informational                             26 March 2019
Expires: 27 September 2019


                       
CMS Content Types for CBOR

                      
draft-schaad-cbor-content-00


Abstract

   CBOR is becoming a widely used method of doing content encoding.  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.

Contributing to this document

   The source for this draft is being maintained in GitHub.  Suggested
   changes should be submitted as pull requests at TBD.  Editorial
   changes can be managed in GitHub, but any substantial issues need to
   be discussed on the COSE mailing list.

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Table of Contents

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


1.  Introduction


   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 the most common method for providing message
   based security, although in many cases the CBOR Object Signing and
   Encryption (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.


2.  CBOR Content Type


   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) pkcs7(7) (x) TBD }

   The CBOR content type is intended to refer to a single object encoded
   using the CBOR encoding format.  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.


3.  CBOR Sequence Content Type


   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) TBD }

   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.


4.  ASN.1 Module


   CborContentTypes
   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) TBD }

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

       -- 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.

   In the SMI Security for S/MIME Content Types registry, add two new
   entries for id-ct-cbor and id-ct-cborSequence that point to this
   document.


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 does mean that id-data does not need to be used to identify
   these content types and thus can reduce confusion.


7.  Normative References


   [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>.

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

Author's Address

   Jim Schaad
   August Cellars

   Email: ietf@augustcellars.com