





Network Working Group                                    L. Dondeti, Ed.
Request for Comments: 4909                                QUALCOMM, Inc.
Category: Informational                                    D. Castleford
                                                          France Telecom
                                                              F. Hartung
                                                       Ericsson Research
                                                               June 2007


      Multimedia Internet KEYing (MIKEY) General Extension Payload
           for Open Mobile Alliance BCAST LTKM/STKM Transport

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document specifies a new Multimedia Internet KEYing (MIKEY)
   General Extension payload (RFC 3830) to transport the short-term key
   message (STKM) and long-term key message (LTKM) payloads defined in
   the Open Mobile Alliance's (OMA) Browser and Content (BAC) Broadcast
   (BCAST) group's Service and Content protection specification.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.  MIKEY General Extension for OMA BCAST Usage . . . . . . . . . . 3
   4.  Interoperability Considerations . . . . . . . . . . . . . . . . 3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5









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1.  Introduction

   The Multimedia Internet Keying (MIKEY) protocol specification [1]
   defines a General Extension payload to allow possible extensions to
   MIKEY without having to allocate a new payload type.  The General
   Extension payload can be used in any MIKEY message and is part of the
   authenticated/signed data part.  There is an 8-bit type field in that
   payload.  The type code assignment is IANA-managed, and RFC 3830
   requires IETF consensus for assignments from the public range of
   0-240.

   The Open Mobile Alliance's (OMA) Browser and Content (BAC) Broadcast
   (BCAST) group's Service and Content Protection specification [2]
   specifies the use of a short-term key message (STKM) and a long-term
   key message (LTKM) that carry attributes related to Service and
   Content protection.  Note that any keys associated with the
   attributes are part of the MIKEY KEMAC payload.  This document
   specifies the use of the General Extension payload of MIKEY to carry
   the LTKMs or STKMs.

   RFC 3830 [1], the MIKEY General Extension payload defined in [3], and
   the 3rd Generation Partnership Project (3GPP)'s Multimedia Broadcast/
   Multicast Service (MBMS) document [4] specify the transport of MIKEY
   messages via unicast or broadcast and the OMA specifications use
   either for transport of MIKEY messages.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [5].

   OMA BCAST STKM/LTKM MIKEY General Extension:  We refer to the General
      Extension type -- 5 -- as the OMA BCAST STKM/LTKM MIKEY General
      Extension .
















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3.  MIKEY General Extension for OMA BCAST Usage

                            1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ! Next   !      Type     !            Length             !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       !       OMA BCAST S/LTKM Subtype  (variable length)      ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 1: OMA BCAST MIKEY General Extension

   Section 6.1 of RFC 3830 specifies the first three fields of the
   General Extension Payload and defines a variable length Data field.
   This document specifies the use of Type 5 for OMA BCAST Service and
   Content Protection using the Smartcard Profile.  The contents of the
   variable length data field are defined below.

   Subtype:  8 bits.  This field indicates the type of the OMA BCAST
      payload.  In this specification, only two values are specified:
      LTKM (1), and STKM (2).

   Subtype Specific Data:  Variable length.  The contents of this field
      are defined in Section 6 of the OMA BCAST Service and Content
      Protection specification [2].


                         1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     !    Subtype    !   Subtype specific data (variable length)     ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: STKM/LTKM Subtype Payload

4.  Interoperability Considerations

   This document specifies the use of MIKEY General Extension Payload
   Type 5 and a couple of subtype values (1 and 2), one each for OMA
   BCAST Service and Content protection's STKM and LTKM payloads.
   Interoperability considerations span several standards bodies, with
   OMA BCAST 1.0 enabler compliance being the key aspect; as such, it is
   up to the OMA test planning to verify the interoperability and
   compliance of OMA BCAST 1.0 implementations.  This payload type
   assignment does not change MIKEY beyond RFC 3830 [1] and RFC 4563
   [3].





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5.  Security Considerations

   According to RFC 3830, the general extension payload can be used in
   any MIKEY message and is part of the authenticated/signed data part.
   The parameters proposed to be included in the OMA BCAST MIKEY General
   Extension payload (listed in Section 3) need only to be integrity
   protected, which is already allowed by the MIKEY specification.  The
   OMA BCAST MIKEY General Extension Payload SHALL be integrity
   protected.  Furthermore, keys or any parameters that require
   confidentiality MUST NOT be included in the General Extension
   Payload.  If keys or other confidential data are to be transported
   via the General Extension Payload, such data MUST be encrypted and
   encapsulated independently.  Finally, note that MIKEY already
   provides replay protection and that protection covers the General
   Extension Payload also.

6.  IANA Considerations

   IANA has allocated a new General Extension Type from the "General
   Extensions payload name spaces" in the IANA registry at
   http://www.iana.org/assignments/mikey-payloads for use by OMA BCAST.
   Furthermore, IANA maintains a list of corresponding subtypes (0-255)
   as follows:

      0 ...  Reserved

      1 ...  LTKM

      2 ...  STKM

      3 ... 191 (maintained by IANA and assigned by IETF Review [6])

      192 ... 255 (Private use)

7.  Acknowledgments

   Many thanks to Jari Arkko, Piron Laurent, and Steffen Fries for their
   reviews and suggestions for improvement.













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8.  References

8.1.  Normative References

   [1]  Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K.
        Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830,
        August 2004.

   [2]  Open Mobile Alliance, "Service and Content Protection for Mobile
        Broadcast Services", OMA TS-BCAST_SvcCntProtection-V1_0-
        20070529-C, 2007, <http://www.openmobilealliance.org/
        release_program/bcast_v1_0.html>.

   [3]  Carrara, E., Lehtovirta, V., and K. Norrman, "The Key ID
        Information Type for the General Extension Payload in Multimedia
        Internet KEYing (MIKEY)", RFC 4563, June 2006.

   [4]  3GPP, "3G Security; Security of Multimedia Broadcast/Multicast
        Service (MBMS)", 3GPP TS 33.246 6.6.0, March 2006.

   [5]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References

   [6]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", Work in Progress, March 2007.
























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Authors' Addresses

   Lakshminath Dondeti (editor)
   QUALCOMM, Inc.
   5775 Morehouse Dr
   San Diego, CA
   USA

   Phone: +1 858-845-1267
   EMail: ldondeti@qualcomm.com


   David Castleford
   France Telecom
   4, rue du Clos Courtel
   35512 Cesson Sevigne Cedex,
   France

   Phone: + 33 (0)2 99 12 49 27
   EMail: david.castleford@orange-ftgroup.com


   Frank Hartung
   Ericsson Research
   Ericsson Allee 1
   52134 Herzogenrath,
   Germany

   Phone: +49 2407 575389
   EMail: frank.hartung@ericsson.com





















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