    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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    RFC 4909           OMA BCAST MIKEY General Extension           June 2007

    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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    RFC 4909           OMA BCAST MIKEY General Extension           June 2007

    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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    RFC 4909           OMA BCAST MIKEY General Extension           June 2007

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    Acknowledgement

       Funding for the RFC Editor function is currently provided by the
       Internet Society.

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