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Network Working Group                                            M. Park
Internet-Draft                                       Soongsil University
Intended status: Informational                         November 20, 2018
Expires: May 24, 2019


                       Multiple group membership
             draft-park-mls-multiple-groups-requirement-00

Abstract

   This document proposes a functional requirement of Message Level
   Security (MLS) which provide an efficient management for multiple
   groups.  Although MLS defines an architecture and an abstract
   protocol for a secure group communication, it overlooks the need of
   multiple groups.  This document describes a usecase of the multiple
   groups, and the need for an efficient multiple group membership
   management.

Status of This Memo

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   This Internet-Draft will expire on May 24, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Re-keying for membership change . . . . . . . . . . . . . . .   2
   4.  Multiple groups scenario  . . . . . . . . . . . . . . . . . .   3
   5.  Multiple group membership . . . . . . . . . . . . . . . . . .   4
   6.  Informative References  . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   With the emergence of diverse group-based applications, e.g. a
   channel-based charged TV or telematics services, multiple group
   applications are likely to coexist, and users may have multiple
   memberships.  Of course, although the functional requirements defined
   in the mls architecture draft can satisfy the multiple membership
   management, we need to consider the efficient management of multiple
   membership.  This document mentions the inefficiency which may occur
   in the multiple membership management and the motivation of the
   functional requirement, multiple group membership.

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 [RFC2119].

3.  Re-keying for membership change

   Let us consider a situation where a member is about to leave a group.
   Before this member leaves, all the members have shared a group key to
   encrypt/decrypt messages among themselves.  After the member leaves,
   the old group key must be revoked and updated with a new group key.
   This rekeying process may cause a lot of key management overhead.
   Since the existing members do not have any shared secret keys except
   for the old group key, a new group key should be distributed to these
   members in a secure manner.  As a result, it is obvious that the more
   the number of users in a group service, the larger the rekeying
   overhead would be.







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4.  Multiple groups scenario

   There can be various group messaging services.  Generally, the group
   messaging services can be considered as the commercial services such
   as a charged TV streaming service, a telematics service, and an
   information service (Sports or stock).  Let us assume these three
   services are Delivery Services (DS) as shown in Figure 1.  In this
   case, there will be at least three groups for the three services,
   each of which should be managed according to the membership records
   of the DSs.  Moreover, if the subscription to a DS is charged for
   either each channel (Ch1, Ch2, and Ch3) or content (sports and
   stock), the service provider should manage the additional user groups
   (e.g., channel-based or content-based groups) for accurate accounting
   like Figure 2.  As a result, the management overhead stemming from
   membership management including rekeying can significantly increase
   due to the number of such groups.

      ----------------      --------------     -----------------
     | A Charged TV   |    | Telematics   |   | Information     |
     |                |    | Service      |   | Service         |
     |<Ch1><Ch2><Ch3> |    |              |   | <Sports> <Stock>|
      ----------------      --------------     -----------------
        \         / \________________           /          |
         \       /              _____\_________/           |
          \     /              /      \                    |
           -------       ------        -------        -------
          | User0 |     | User1 |     | User2 |      | User3 |
           -------       ------        -------        -------

                    Figure 1: Multiple groups scenario

      Ch1 group          Ch2 group         Ch3 group
      ****************   ****************  ****************
      * -------      *   * -------      *  * -------      *
      *| User0 |  ...*   *| User1 | ... *  *| User2 | ... *
      * -------      *   * -------      *  * -------      *
      ****************   ****************  ****************

      Telematics group   Sports group      Stock group
      ****************   ****************  ****************
      * -------      *   * -------      *  * -------      *
      *| User2 |  ...*   *| User1 | ... *  *| User3 | ... *
      * -------      *   * -------      *  * -------      *
      ****************   ****************  ****************

                   Figure 2: Six delivery service groups





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5.  Multiple group membership

   The multiple group scenario in the previous section can be
   implemented with multiple independent groups, where each service
   group has an independent AS.  However, a single service provider may
   manage multiple groups, e.g., multiple channel groups in a channel-
   based charged service.  In this case, the service provider should
   have multiple independent groups corresponding to each channel, which
   may increase the management cost such as many Ass as the number of
   groups and re-keying.  Therefore, the protocol should be able to
   allow a single Authentication Service to manage multiple group
   memberships in order to support more than two Delivery Services as
   shown in Figure 3.

       ----------------      --------------     --------------
      | Authentication |    | Delivery     |   | Delivery     |
      | Service (AS)   |    | Service(DS1) |   | Service(DS2) |
       ----------------      --------------     --------------
      Multiple memberships /                 \       / |
      *********************************************************
      *                  /             ________\___/   |       *
      *                 /             /         \      |       *
      *      ----------       ----------       ----------     *
      *     | Client 0 |     | Client 1 |     | Client N |    *
      *      ----------       ----------       ----------     *
      *      ............................      ...........    *
      *      Member 0                          Member 1       *
      *                                                       *
      *********************************************************

                       Figure 3: Multiple membership

6.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.















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Appendix A.  Acknowledgements

   This work was supported by Institute for Information & communications
   Technology Promotion(IITP) grant funded by the Korea government(MSIT)
   (No.2018-0-00254, SDN security technology development).

Author's Address

   Minho Park
   School of Electronic Engineering
   Soongsil University
   369, Sangdo-ro, Dongjak-gu
   Seoul, Seoul  06978
   Republic of Korea

   Phone: +82 2 828 7176
   EMail: mhp@ssu.ac.kr


































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