RFC 4909

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

📅 published June 2007, from ietf

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

okay bestie, the title block first because it's the whole vibe 💖 This is RFC 4909, published June 2007 by L. Dondeti (editor) of QUALCOMM, Inc., D. Castleford of France Telecom, and F. Hartung of Ericsson Research. It's in the Network Working Group, and the category is Informational. The title block doesn't list anything it obsoletes or updates, so it's a standalone doc 🫶

Status of This Memo ✨

This memo gives information to the Internet community. It is NOT a spec for any kind of Internet standard, and it can be distributed freely with no limits 🌸

Copyright Notice 🦋

Abstract 💅

This doc specifies a new MIKEY General Extension payload, defined in [RFC3830]-land (RFC 3830), that carries the short-term key message (STKM) and long-term key message (LTKM) payloads. Those are defined in the Open Mobile Alliance's (OMA) Browser and Content (BAC) Broadcast (BCAST) group's Service and Content protection spec, so it's basically a delivery truck for them 🚚✨

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

1. Introduction 🌈

okay so MIKEY ([1]) has a General Extension payload that lets you add extensions to MIKEY without needing a brand-new payload type 🔥 It can go in any MIKEY message, and it's part of the authenticated/signed data. The payload has an 8-bit type field. The type code assignments are managed by IANA, and RFC 3830 says assignments from the public range 0-240 need IETF consensus 💜

OMA's BCAST group has a Service and Content Protection spec ([2]) that uses an STKM and an LTKM to carry attributes for service and content protection. Any keys tied to those attributes live in the MIKEY KEMAC payload 🔐 This doc says to use the MIKEY General Extension payload to carry the LTKMs or STKMs.

[1] (RFC 3830), the MIKEY General Extension payload defined in [3], and the 3rd Generation Partnership Project (3GPP)'s Multimedia Broadcast/Multicast Service (MBMS) document [4] all describe how MIKEY messages get transported, by unicast or broadcast. The OMA specs use either one for transport ✨

2. Terminology 💖

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this doc are read as described in RFC 2119 [5] 🎀

OMA BCAST STKM/LTKM MIKEY General Extension: we call General Extension type 5 the OMA BCAST STKM/LTKM MIKEY General Extension 🍓

3. MIKEY General Extension for OMA BCAST Usage 🦋

Here's the layout of the OMA BCAST 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

so Section 6.1 of RFC 3830 defines the first three fields of the General Extension Payload and a variable-length Data field. This doc uses Type 5 for OMA BCAST Service and Content Protection with the Smartcard Profile. The variable-length data field contents are defined below 🫶

Subtype: 8 bits. It tells you what kind of OMA BCAST payload you're looking at. Only two values are defined here: LTKM (1) and STKM (2) 💅

Subtype Specific Data: variable length. What goes in here is defined in Section 6 of the OMA BCAST Service and Content Protection spec [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 doc uses MIKEY General Extension Payload Type 5 with two subtype values, 1 and 2, one each for the STKM and LTKM payloads in OMA BCAST Service and Content protection. Interoperability spans a few standards bodies, and OMA BCAST 1.0 enabler compliance is the big one. So it's up to OMA test planning to check interop and compliance for OMA BCAST 1.0 implementations 🔥 This payload type assignment doesn't change MIKEY beyond RFC 3830 [1] and RFC 4563 [3].

5. Security Considerations 💀

Okay, this section is serious, so buckle up 😭 According to RFC 3830, the General Extension payload can go in any MIKEY message and is part of the authenticated/signed data. The parameters proposed for the OMA BCAST MIKEY General Extension payload (listed in Section 3) only need integrity protection, which MIKEY already allows. The OMA BCAST MIKEY General Extension Payload SHALL be integrity protected. Keys or any parameters that need confidentiality MUST NOT be included in the General Extension Payload. If keys or other confidential data have to go through the General Extension Payload, that data MUST be encrypted and encapsulated independently. And finally, MIKEY already gives replay protection, and that covers the General Extension Payload too 🔐🔐

⚠️ The key words in this section are the whole point, so don't skip them. Confidential data never goes straight into the General Extension Payload.

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 OMA BCAST use. IANA also keeps a list of matching subtypes (0-255), like this 📋

   0 ...  Reserved

   1 ...  LTKM

   2 ...  STKM

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

   192 ... 255 (Private use)

7. Acknowledgments 💜

Huge thanks to Jari Arkko, Piron Laurent, and Steffen Fries for their reviews and suggestions 🫶

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.

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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Acknowledgement 🧚

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