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Core Working Group                                                   J. Zhu
Internet Draft                                                        M. Qi
Intended status: Informational                                 China Mobile
Expires:March 29, 2014                                         Sep 29, 2013


                            Group Authentication
                          draft-zhu-core-groupauth-01

Abstract
   The group communication is designed for the communication of Internet
   of Things. A threat is identified in [I-D.ietf-core-groupcomm] that
   current DTLS based approach is unicast oriented and there is no
   supporting on group authentication feature. Unicast oriented
   authentication will causing serious burden when a large number of
   terminal nodes will be involved inevitably. In another aspect, some
   terminals will own the same characteristics, such as owning same
   features, in the same place, working in the same time, etc. With this
   mechanism, all terminals can be authenticated together with little
   signaling and calculation at the same time. It will reduce the
   network burden and save time. This draft describes the security of
   group authentication and an group authentication implementation
   method for the Internet of things.

Status of this Memo
   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
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   This Internet-Draft will expire on March 29, 2014.

Copyright Notice
   Copyright (c) 2013 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 Provisions
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   in effect on the date of publication of this document.  Please
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Table of Contents

   1. Introduction .....................................................2
   2. Conventions used in this document ................................3
   2.1. Definitions.....................................................3
   3. Problem Statement ................................................4
   3.1. Use cases ......................................................4
   3.2. Problem statement ..............................................5
   4. Requirement ......................................................6
   5. Group Authentication Solution ....................................7
   5.1. Introduction ...................................................7
   5.2. Detailed group scenario description ............................7
   5.3. Group scenario procedure .......................................9
   6. Security Considerations .........................................10
   7. IANA Considerations .............................................11
   8. Conclusions .....................................................11
   9. Acknowledgement..................................................11
   10. References .....................................................11
   10.1. Normative References .........................................11
   10.2. Informative References .......................................11

1. Introduction
   With the development of Internet of Things, a large number of


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   terminal nodes will be involved inevitably. The unicast
   authentication communication from big amount terminals will merge
   together in the network, and causing serious burden to the server.
   Although IP multicast technical is introduced for group communication
   in [I-D.ietf-core-groupcomm], IP multicast relies on the unicast
   authentication at initial stage. In another aspect, some terminals
   will own the same characteristics, such as owning same features, in
   the same place, working in the same time, etc. With this mechanism,
   all terminals can be authenticated with little signaling and
   calculation at the same time. It will reduce the network burden and
   save time.

   This draft describes the security of group authentication and an
   group authentication implementation method for the Internet of things.

2. Conventions used in this document

   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 [RFC2119].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS. Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

2.1. Definitions
   Terminals: It is such a constrained device also recognized as group node
   in this document which communicates with server, through direct or
   indirect connections, which can be seen by the server. If some constrained
   devices like Zigbee node only communicates with sink node and it can't
   be seen by the server, such constrained device is not recognized as
   terminal.

   Group agent: It is a device on behalf of group nodes (terminals) to
   make mutual authentication with network server.

   Network server: It is the core network server which is responsible for
   authenticating the legality of terminal and provides specific services
   for them.

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3. Problem Statement

3.1. Use cases
   Nowadays the normal authentication mechanism in network is a
   traditional unicast authentication method between a single terminal
   and a single network entity. The authentication mechanism will be
   finished based one 1-2 round of challenge-response conversation separately.
   If there are many terminals, the cost for authentication will be increased.

   Now for some M2M service, it may be a large amount of terminal used for
   an M2M service. These terminals are placed in the same location, will
   be used for the same purpose, and own same behavior. These terminals
   can be worked together as a group. In these scenarios, the existing
   authentication mechanism is no longer appropriate. When a large number of
   terminals want to access network server, huge number of authentication
   signaling will be generated by the unicast authentication method.
   What is more, it will cause network congestion and lead to DoS attack. For
   some terminal devices which is restricted with limited computing capability
   and power, the traditional unicast authentication will increase the
   computational burden of these terminals and drain their poor battery.

   The following use cases are identified at this point:

   Smart Metering: A large amount of smart power meter terminals are deployed
   in a block. The smart meter uploads meter report frequently through the
   network to smart meter server. What is more, smart meter server queries
   all terminals periodically to check whether the terminal is workable or not.
   So smart meters report at the same time, or the smart meter server need to
   re-configure all smart meters at the same time. In fact, there are
   other type of smart metering which has no agent node. This will lead
   to overload since each apartment needs to equip with a meter and they
   access network parallel at the same time and it will not be considered
   in this draft.

   Remote Vehicle Management: IOT terminals contains GPS location reporter,
   remote air condition control, etc. would be installed in some special
   Vehicles like Taxi. It will send information such as position information,
   navigation, remote diagnosis, on-board communication, news and

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   entertainment information etc. to the network server in order to make
   better vehicle scheduling, vehicle monitoring and vehicle controlling. So
   it needs to connect to the network and make authentication at first.
   However, such vehicles would gather in a small place like airport, train
   station, etc. The frequency of connection from these terminals to server
   will cause overloading.

   Intelligent home: various sensors equipped with communication modules
   are deployed in a house to monitor house conditions and make a
   control when necessary. These sensors collect and report house
   related information like the status of door open/close, indoor temperature
   to its owner through a network, and take actions by following the
   regulating instructions send by the owner.

3.2. Problem statement

   In the current smart metering service use cases, a large amount of
   smart power meter terminals are deployed in a block. The smart meter
   uploads meter report frequently through the network to smart meter
   server. What is more, smart meter server queries all terminals
   periodically to check whether the terminal is workable or not.
   Therefore, the meter requires frequent and network communication.

   In such use cases, when all the meters access network parallel at the
   same time, or when the server sends message to all meters, the
   terminals will connect to the network in a short time period (1sec ~
   1min). Assume there are 19 buildings in the block, and each building
   has 25 floors on average with 10 apartments in each floor. If each
   apartment is equipped with 1 smart power meter, then 4760 meters will
   be deployed in total in the block. This will cause pressure to the
   network.

   So an agent node has been introduced to aggregate the message from
   these meters and then send out these meters data to the server
   together. After the agent is introduced, the connection between
   meters and servers is split into two parts: one is the connection
   between meters, the other is and the one between agent and server.
   Usually the agent is responsible for the authentication of the meters.


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   The server is responsible for the authentication of the agent only
   and gets all information about meters such as ID, data, from agent.

   The current security mechanism is:
   1. Each meter is authenticated with the agent. Agent will
      authenticate the meter one by one. After that, agent should make
      mutual authentication with server. Then server can confirm agent
      identity.

   2. Meter will set up security connection with agent, and agent will
      also set up security connection with server. When a meter wants to
      send data to server. It should send the data confidential
      protected to agent first. Agent will decrypt the data and transfer
      it to server by using the security protection mechanism between
      agent and server.

   However, this procedure has the following security problems:
   1. Since all meters are authenticated by the agent and no direct
      authentication from server to meter. The server can get meter's ID
      and data only through agent. So the agent Due to the key position
      in the authentication, the security protection about agent is very
      important. Server could not authenticate meters directly. It can
      only rely on the agent. However, the agent would be placed in
      un-secure place or owned by different user rather than the server
      owner. If the agent is compromised or lay to server, agent can act
      as a middle attacker that makes fake authentication to meters and
      report fake ID to servers.
   2. Another security problem is related with agent and server. Under
      this scenario, all information from meters will be transferred
      through agent. So agent will know all information generated by
      meters. However, under some scenario, agent would be owned and
      used by different user other than the meters' and servers' owner.
      So under this assumption, the agent should not get the message
      from meter to server. So meters should set up an secure end-to-end
      tunnel with server. It should request another authentication and
      key generation procedure in addition to authenticate with agent.
      This will bring complexity and overhead to the system.

4. Requirement

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   In order to reduce the cost and simplify a lot of overhead with the
   same characteristics of these groups of meter or sensor node group-
   based operations, it is needed to provide group authentication. For
   example, when smart meters perform bulk configuration information
   updates, it is needed to ensure that the correct identity of the user
   node within the group, to prevent the configuration information is
   wrong node receives. In addition, when smart meters report meter
   readings to the electricity system platform, it is also needed to be
   able to prove the correctness of the identity of smart meters, to
   prevent malicious node reporting false readings.

5. Group Authentication Solution
5.1. Introduction

   Group authentication is a kind of authentication technologies that a
   group of users or terminals can be authenticated together at the same
   time. Instead of authenticating a number of terminals of a group one
   by one, group authentication mechanism treats these terminals in the
   group as a whole, and authenticates them together. Each group has a
   unique identifier, and an agent, which can be called as group agent,
   group gateway, etc.

   Group authentication comprises following two phases as following:

   1. The first phase is that user/terminal should be authenticated
      whether it belongs to a given group. This can be implemented
      through the proprietary authentication technology in a group, such
      as Zigbee or any others.

   2. The second phase is that mutual authentication should be made
      between a given network entity, and a group agent who is
      responsible to delegate all terminals in the group.

      After the authentication, terminals and network entity can
      generate separated session keys individually if there is some
      demand to make individual communication between network entity and
      each terminal.

5.2. Detailed group scenario description

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   For group authentication, there is detailed network description as
   following. There are 5 nodes inside a given group. They are A1, A2,
   A3, A4, and A5 which is group agent. And the given group can be named
   as group A. All nodes in group A can communicate with each other.
   What is more, A5 is able to communicate with network entity directly.
   Network entity will store the group information, such as identifiers,
   root keys used for all nodes inside the group. Network entity is also
   responsible for generating group authentication vector. The scenario
   is shown as below.
   +-------------------------------------------------------+
   |                                                       |
   | +-------+                                             |
   | |  A1   |<---------+                                  |
   | +-------+          |                                  |
   |  ^   ^             |                                  |
   |  |   |             |                                  |
   |  |   |             |                                  |
   |  |   |             |                                  |
   |  |   |             |                                  |
   |  |   |             |                                  |
   |  |   V             V                                  |
   |  | +----+       +-----+      +---------------+        |
   |  | | A2 |<----->| A5  |<====>|Network server |        |
   |  | +----+       +-----+      +---------------+        |
   |  |  |           ^  ^  ^                               |
   |  |  |  +--------+  |  +---+                           |
   |  |  |  |           |      V                           |
   |  |  |  |           |   +----+                         |
   |  |  |  |           |   | A4 |                         |
   |  V  V  V           |   +----+                         |
   |  +------+          |                                  |
   |  |  A3  |<---------+                                  |
   |  +------+                                             |
   +-------------------------------------------------------+
          Figure 1 Group Authentication Architecture
   o  A5 (group agent) communicates with other nodes, i.e. A1, A2, A3,
      A4 by inner group protocol.  All nodes should contain such models
      as inner group communication model, group authentication mode.
      Inner group communication model can be used to sending/receiving

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      the group authentication message. Group authentication model can
      be used to generate authentication vectors/response and to
      authenticate peers.
   o  Group agent will make mutual authentication with network entities.
      There are two kinds of network entities. Network server is
      responsible for mutual authentication action with group agent. And
      Network Server is responsible for group authentication
      vector generation and forwarding AV to network server.
      After the authentication, terminals and network entity can
      generate separated session keys individually if there is some
      demand to make individual communication between network entity and
      each terminals.



   o  Group agent who represents the whole group, communicates with
      network entity, and generate group session key through
      authentication with the network server.
   o  Pre-configure of the group
   All the group nodes should be configured with sub key k_1, k_2, k_3,
   k_4, k_g, which will be used for mutual authentication in the group
   and separated communication.

5.3. Group scenario procedure

   As mentioned above, group authentication can be divided into two
   phases.

   In the first phase, group member, say Ai, sends authentication
   request to group agent at first as following.
   1. Group member Ai sends message to trigger authentication at first.
   2. Group agent sends authentication request to each group member.
   3. Group member Ai verifies group agent at first. If success, Ai will
      generate session key for the communication with group agent, and
      sends response containing such session key back to group agent. If
      not success, the authentication is failed and group authentication
      procedure will be abort.
   4. Group agent authenticates each group member Ai through the
      response message and record the authentication result in a mapping

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      table.
   After the inner group authentication, all of group members are
   authenticated by group agent, and second phase can be performed.

   5. Group agent sends message to network server to trigger the
      authentication outside the group.

   6. Meanwhile, group agent sends authentication vector request to network
      server with group agent identity.


   7. Network Server will generate authentication vector
      according to group agent identity.
   8. What is more, network server should be able to recognize
      that is a group authentication is performed based on group agent
      identity. Network Server will generate session key for each
      group members by using pre-configured group member information and
      the same keying material in above step.
   9. Network Server will send such authentication vector and
      session keys together back to network server.
   10.Network server will perform mutual authentication with
      group agent.
   11.Group agent authenticate group agent and send authentication
      response back to network server.
   12.Network server authenticates group agent. If success, it
      can be considered that group agent and all group terminals is
      authenticated successfully.
   13.Group agent will communicate with network server to choose
      the confidential and integrity protection algorithms.
   14.After that, group agent will send keying material, selected
      algorithms to each group member.
   15. Group member will generate session keys.

   After these two phases, each terminal is authenticated with network
   server and generate independently session key with network
   server.

6. Security Considerations
   TBD

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7. IANA Considerations
   There are no IANA considerations associated to this memo.

8. Conclusions

      This memo describes the problem raised by using one-to-one
      authentication for huge number of Internet of Things terminals.
          After that, group authentication requirement is raised and a group
      authentication mechanism is proposed. By using the proposed group
          authentication mechanism, the exploited group agent can behalf of
          all involved group nodes to make mutual authentication with network
          server, but the agent can not realize the content transmitted between
          both of them since it is just a intermediate node to forward messages
          which are encrypted by specific session key between the group node and
          network server. The trust relationship is between group nodes and
          network server. After authentication, the trust relationship between
          group nodes and group agent are not needed.


   9. Acknowledgement

      Thanks very much to Bert Greevenbosch, Stefanie Gerdes, Kepeng Li for
          their helpful comments and significant suggestions to revise this
          document.


   10. References
   10.1. Normative References
   10.2. Informative References

Authors' Addresses
   Judy Zhu
   China Mobile
   Unit 2, 32 Xuanwumenxi Ave,
   Xicheng District,
   Beijing 100053, China
   Email: zhuhongru@chinamobile.com



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   Minpeng Qi
   China Mobile
   Unit 2, 32 Xuanwumenxi Ave,
   Xicheng District,
   Beijing 100053, China
   Email: qiminpeng@chinamobile.com
































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