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).
AbstractThis 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. 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
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  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 , the MIKEY General Extension payload defined in , and the 3rd Generation Partnership Project (3GPP)'s Multimedia Broadcast/ Multicast Service (MBMS) document  specify the transport of MIKEY messages via unicast or broadcast and the OMA specifications use either for transport of MIKEY messages. RFC 2119 . OMA BCAST STKM/LTKM MIKEY General Extension: We refer to the General Extension type -- 5 -- as the OMA BCAST STKM/LTKM MIKEY General Extension .
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 . 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 RFC 3830  and RFC 4563 .
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]) 192 ... 255 (Private use)
 Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K. Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830, August 2004.  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>.  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.  3GPP, "3G Security; Security of Multimedia Broadcast/Multicast Service (MBMS)", 3GPP TS 33.246 6.6.0, March 2006.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", Work in Progress, March 2007.
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