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Core                                                         B. Sarikaya
Internet-Draft                                                Huawei USA
Intended status: Informational                                   Y. Ohba
Expires: May 14, 2011                                            Toshiba
                                                                  Z. Cao
                                                            China Mobile
                                                               R. Cragie
                                                Pacific Gas and Electric
                                                       November 10, 2010


         Security Bootstrapping of Resource-Constrained Devices
                 draft-sarikaya-core-sbootstrapping-00

Abstract

   The Internet of Things is marching its way towards completion.  Nodes
   can use standards from the 6LoWPAN and ROLL WG to achieve IP
   connectivity.  IEEE Standards ensure connectivity at lower layers for
   resource-constrained devices.  Yet a central problem remains at a
   more basic layer without a suitable answer: how to initially
   configure the network.  Without configuration the network never
   advances beyond a large box of nodes.  Current solutions tend to be
   specific to a certain vendor, node type, or application.

   This document outlines exactly what problems are faced in solving
   this problem.  General problems faced in any low-power wireless
   network are outlined first; followed by how these apply to
   bootstrapping.  A selection of currently proposed techniques is
   presented.  From these a more generic approach is presented, which
   can solve the problem for a wide range of situations.

   An emphasis is on performing this bootstrapping in a secure manner.
   This document does not cover operation of the network securely.  This
   document does provide the basis for allowing the network to operate
   securely however, by providing standard methods for key exchanges and
   authentication.

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).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.




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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on May 14, 2011.

Copyright Notice

   Copyright (c) 2010 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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   described in the Simplified BSD License.






























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  What is Bootstrapping? . . . . . . . . . . . . . . . . . .  5
     1.2.  Why IETF?  . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Bootstrapping Architecture . . . . . . . . . . . . . . . . . .  6
     2.1.  Areas of Boostrapping  . . . . . . . . . . . . . . . . . .  6
     2.2.  Architecture . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Communications Channel . . . . . . . . . . . . . . . . . . . .  8
     3.1.  Supported Communication Channels . . . . . . . . . . . . .  8
   4.  Bootstrap Security Method  . . . . . . . . . . . . . . . . . .  8
     4.1.  None . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.2.  Asymmetric with User Authentication, Followed by
           Symmetric  . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.3.  Asymmetric  with Certificate Authority, Followed by
           Symmetric  . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.4.  Cryptographically Generated Address Based Address
           Ownership Verification . . . . . . . . . . . . . . . . . .  9
   5.  Bootstrap Protocols  . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  System Level Objectives  . . . . . . . . . . . . . . . . . 10
     5.2.  EAP Authentication Framework . . . . . . . . . . . . . . . 10
     5.3.  PANA . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     5.4.  HIP-DEX  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.5.  802.1X . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Examples of Node Configuration  . . . . . . . . . . . 19
     A.1.  Smart Energy . . . . . . . . . . . . . . . . . . . . . . . 19
       A.1.1.  Initial Meter Installation . . . . . . . . . . . . . . 19
       A.1.2.  Home Expansions  . . . . . . . . . . . . . . . . . . . 19
     A.2.  Consumer Products  . . . . . . . . . . . . . . . . . . . . 20
       A.2.1.  Connecting DVD Remote to DVD Player  . . . . . . . . . 20
       A.2.2.  Adding a TV to a network with a DVD player and
               remote . . . . . . . . . . . . . . . . . . . . . . . . 20
       A.2.3.  Providing GPS Location Data  . . . . . . . . . . . . . 20
     A.3.  Commercial Building Automation . . . . . . . . . . . . . . 20
       A.3.1.  Light Installation . . . . . . . . . . . . . . . . . . 20
   Appendix B.  Example Exchanges . . . . . . . . . . . . . . . . . . 20
     B.1.  Smart Energy: Meter Manufacture  . . . . . . . . . . . . . 20
     B.2.  Smart Energy: Meter Installation . . . . . . . . . . . . . 20
     B.3.  Smart Energy: Home Expansion . . . . . . . . . . . . . . . 21
     B.4.  Consumer: Connecting DVD Remote to DVD Player  . . . . . . 21
     B.5.  Consumer: Adding a TV to a network with a DVD player
           and remote . . . . . . . . . . . . . . . . . . . . . . . . 22



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     B.6.  Consumer: Providing GPS Location Data  . . . . . . . . . . 24
     B.7.  Commercial: Building Automation  . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
















































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1.  Introduction

   Familiarity with constrained network types is assumed here.
   Documents produced in the 6LoWPAN, ROLL, and CoRE Working Groups
   (WGs) would be a useful reference for the reader.  In particular RFC
   4919 [RFC4919] from 6LoWPAN, RFC 5548 [RFC5548] and RFC 5673
   [RFC5673] from ROLL, CoAP [I-D.ietf-core-coap] from CoRE, and a paper
   by Romer and Mattern [ROMER04].  Familiarity with application
   specific examples such as Zigbee or Smart Energy groups is assumed.

   A summary of those will be presented, as far as network requirements
   are concerned.  The general network requirements will be further
   concentrated into requirements surrounding only the bootstrapping
   issues.

   A number of solutions which are currently in use will be presented.
   Requirements on each solution will be stated to enable their use as a
   security bootstrapping protocol.

1.1.  What is Bootstrapping?

   Node configuration is known as bootstrapping in this document.
   Bootstrapping is any processing required before the network can
   operate.  Typically this will require a number of settings to be
   transferred between nodes at all layers.  This could include anything
   from link-layer information (i.e., wireless channels, link-layer
   encryption keys) to application-layer information (i.e., network
   names, application encryption keys).

   Bootstrapping is complete when settings have been securely
   transferred prior to normal operation in the network.

1.2.  Why IETF?

   The bootstrapping problem is not specific to any MAC or PHY.  This
   problem exists across any two nodes which have no previous knowledge
   of each other.  In particular, this problem is complicated when the
   nodes are resource-constrained and may not have an advanced user
   interface.  The IETF is instrumental in defining standards which will
   be used by The Internet of Things.  Ensuring these standards can be
   used across nodes and networks requires some form of bootstrapping
   which any node can use.

   Existing standards will be used as much as possible in this document.
   The method proposed here should work across many different underlying
   layers.  It could be used to allow two nodes on the same physical
   network to join at the physical layer, or allow two nodes on an
   incompatible physical network to join at the IPv6 layer.



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2.  Bootstrapping Architecture

2.1.  Areas of Boostrapping

   In order to provide a flexible architecture, the bootstrapping method
   is split into five distinct areas and two distinct phases.  The five
   areas are a 'user interface', 'bootstrap profile', 'security method',
   'bootstrap protocol', and the 'communications channel'.

   The phases are provisioning phase and bootstrapping phase.  In the
   provisioning phase, statically configured parameters (e.g.,
   certificates) needed for the bootstrapping phase is provisioned.  In
   the bootstrapping phase, dynamically configured information is set up
   using the statically configured information provided in the
   provisioning phase.

   The user interface provides both user input and user output.  Simple
   nodes may only have a push-button and LED, more complex nodes may
   have a graphical display and keyboard.  The user interface provides
   interaction between the user and bootstrapping methods.  The user
   interface would be used during bootstrapping as an OOB channel.  It
   may also be used to specify bootstrapping policies.

   The user interface provides the interaction between the user and the
   bootstrap protocol.  The user interface will vary depending on the
   capabilities of the node.  Examples might include a push-button and
   LED on simple nodes, to full-blown graphical user interfaces.  Note
   that a 'bootstrapping tool' used to initially deploy a network is
   just a special user interface.  This allows a very uniform protocol
   in deployment and use of networks.

   User interface is out-of-scope and will not be further discussed.

   Two nodes communicate through some channel.  For our purposes this is
   split into the 'control channel' and 'data channel'.  The control
   channel is used for the bootstrap protocol, and the data channel is
   used during normal network operation.  A node may support multiple
   control or data channels.  When the control and data channels are the
   same, the bootstrapping is done In Band (IB).  When the control and
   data channels are different, the bootstrapping is performed Out Of
   Band (OOB).  An 802.15.4 network for instance would use an 802.15.4
   control channel for IB bootstrapping, but a control channel of
   perhaps IrDA or USB for OOB bootstrapping.

   The 'bootstrap profile', i.e. statically configured parameters during
   the provisioning phase, defines what information should be exchanged
   during the process.  A single node may run the protocol multiple
   times with different profiles.  If the user wishes to associate a new



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   lightswitch, the protocol is first run with the '802.15.4 Wireless
   Profile', through which it learns the channel and PAN-ID.  The node
   then runs a 'Security Exchange Profile' to learn the needed
   encryption keys.  Finally it runs a 'Lightswitch Association Profile'
   through which it learns which light to associate with.

   The 'security method' defines supported security methods for
   bootstrapping.  The supported security methods will depend on the
   control channel and bootstrap profile.  In one node if the control
   channel is secure, then a simple clear-text security method is
   supported.  For example when a physical connection between two nodes
   is used, the control channel is considered secure.  However when the
   control channel is not secure, this clear-text security method is not
   supported.  The 'bootstrap profile' additionally defines allowed
   security methods.  Higher security nodes may outlaw ever performing a
   clear-text exchange, even if the control channel is deemed secure.

   The 'bootstrap protocol' defines the actual messages exchanged during
   bootstrapping.  The messages are used to transfer between nodes data,
   node information, and network state.  The selected security method
   runs on top of the control channel, such as EAP-GPSK etc.

2.2.  Architecture

   Security bootstrapping architecture is structured in a hierarchy of
   nodes going from the least resource constraint to the most resource
   constraint.  At the top there is a root node.  The root node is
   called Coordinator or Trust Center in Zigbee and 6LowWAN Border
   Router (6LBR) in 6LoWPAN ND.

   At the next level there are interior Routers.  Routers are able to
   run a routing protocol between other routers and the root.  Router
   are called 6LowWAN Routers (6BR) in 6LoWPAN ND.

   At the lowest level there are the nodes.  The nodes do not run a
   routing protocol.  They can connect to the nearest router over a
   single radio link.  The nodes are called End Device in Zigbee and
   host in in 6LoWPAN ND.

   Routers first join the network as a node and go through security
   bootstrapping operations in order to create a Master Session Key
   (MSK).  Next routers execute routing protocol, e.g.
   [I-D.ietf-roll-rpl] specific steps to create session keys with their
   neighbors and to establish upstream and downstream next hop parents.

   At each node hierarachy level described above, there are lower-layer
   and higher-layer protocols to bootstrap their ciphering keys, where
   the lower-layer refers to layers below IP layer including IEEE



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   802.15.4 MAC layer and LoWPAN adaptation layer and the higher-layer
   refers to IP layer and the above.  In general, required bootstrapping
   procedures depend on the bootstrapping protocols to use.  Section
   Section 5 describes the bootstrapping procedures where EAP
   (Extensible Authentication Protocol) [RFC3748] and other protocols
   are used as the bootstrapping protocols.


3.  Communications Channel

   The communications channel is the method used between two nodes to
   communicate.  There are two main communication channels: the
   'control' and 'data' channels.  The control channel is used during
   bootstrapping, and the data channel is used during network operation.

3.1.  Supported Communication Channels

   There is no limit on what communications channels are supported.  The
   following gives an example of several supported channels:

   o  IEEE 802.15.4

   o  Power-Line Communications

   o  IrDA

   o  RFID

   o  Some simple physical link

   o  Cellular

   o  Ethernet

   o  IPv6

   o  Wi-Fi

   Depending on the node's function, it may use different channels as
   the data or control channel.  Nodes may have multiple data and/or
   control channels as wel.


4.  Bootstrap Security Method

   The bootstrap security method defines allowable security methods.  A
   node may choose to support or use a subset of these methods.  This is
   NOT the security architecture used for the application, but only the



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   security used during bootstrapping.  Typically some high-security
   method is used to generate a shared secret, which then switches to
   simplier symmetric encryption to secure the actual bootstrapping
   channel.  The techniques negotiated should take advantage of hardware
   resources available, such as hardware encryption accelerators on an
   end node.

4.1.  None

   This is the simplist security method.  No encryption or
   authentication is provided, messages are exchanged completely in
   clear-text.  It is assumed some other layer provides security, such
   as a physical connection between devices.

4.2.  Asymmetric with User Authentication, Followed by Symmetric

   A Diffie-Hellman style key exchange is used to generate a shared
   secret.  The authentication will be provided by the user, by
   confirming cryptographic signatures between two devices.  With the
   shared secret generated through the DH, some symmetric encryption is
   used to secure the actual bootstrapping channel.

4.3.  Asymmetric  with Certificate Authority, Followed by Symmetric

   Public key exchanges are used (aka: DH again), but with a Certificate
   Authority.  Once a shared secret exists, symmetric encryption is used
   to secure the actual bootstrapping channel.

4.4.  Cryptographically Generated Address Based Address Ownership
      Verification

   A node may generate the global unique address using different
   techniques other than the stateless address autoconfiguration.  For
   example, Cryptographically Generated Addresses (CGA) [RFC3972] is a
   type of global unique address that can be used to verify the address
   ownership.  When the node uses CGA, it MUST execute SeND protocol
   [RFC3971].  In a 6LOWPAN network, a modified 6LOWPAN ND Protocol
   [I-D.ietf-6lowpan-nd] must be executed between the node and the edge
   router.


5.  Bootstrap Protocols

   In this section we first present system level objectives that
   security bootstrapping protocols are expected to achieve.  Next, we
   present EAP authentication framework and then describe three
   different protocols.




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5.1.  System Level Objectives

   Authentication/ reauthentication: nodes joining the network MUST at
   the first place authenticate to the trust center.  In order to
   achieve secure multi-hop routing, the node MUST authenticate to its
   upstream and downstream neighbors.  A bootstrapping solution MUST
   support re-authentication of resource-constrained devices and re-
   keying of dynamically generated keys.

   Data Confidentiality: the data communication between two endpoints
   MAY be encrypted using the derived key, avoiding being eavesdropped
   by a non-trusted third part.

   Data Integrity: the data communication between two endpoints MUST NOT
   be altered by some intermediate nodes.  The nodes should be able to
   detect the non-integral data.

   Keys and key freshness: the keys used for data communication MUST
   have a lifetime, in order to keep their freshness.  A bootstrapping
   solution MUST support both symmetric and asymmetric key
   authentication.  If distribution of a key to be used for a resource-
   constrained device is required, a bootstrapping solution MUST support
   secure key distribution to prevent the key from eavesdropping,
   alternation and replay attacks.

   Multi domain support: A bootstrapping solution MUST be able to allow
   resource-constrained devices that may be subscribed to different
   administrative domains to be connected to the same access network at
   the same time.

   Identities: A bootstrapping solution MUST be able to allow a
   resource-constrained device to use various types of identities used
   for authentication, including device identities, user identities or
   combinations of different types of identities.  Also a bootstrapping
   solution MUST be able to allow a resource-constrained device to
   change its identities used for authentication over time.

   Authentication infrastructure: A bootstrapping solution MUST be able
   to operate with or without an authentication infrastructure.

5.2.  EAP Authentication Framework

   In EAP, there are three distinct entities: the client or EAP peer,
   the authenticator and the authentication or EAP server [RFC5247].

   The EAP peer is the node that requires to be authenticated before
   being admitted to the network.  The authentication server is the
   device authenticating the node for bootstrapping.  The authenticator



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   is the device that is admitting the node to the network and it
   resides in between the peer and authentication server.

   EAP client and EAP server exchange EAP messages to execute the
   authentication algorithm, a.k.a.  EAP method.  The authenticator is
   responsible for forwarding EAP messages between the client and
   server.  In 802.1X, EAP messages are carried in Layer 2 and in PANA
   in IP or Layer 3.  EAP messages between the authenticator and
   authentication server are carried using AAA protocols (RADIUS or
   Diameter).

   At the end of a successful EAP method execution a master session key
   (MSK) is generated at both the EAP peer and EAP server.
   Authenticator receives MSK from EAP server at the end of EAP method
   execution using key transport.  MSK is used in deriving a session key
   between the node and the authenticator using a protocol called secure
   association protocol (SAP).  Derivation of the session key terminates
   bootstrapping of a node.

   Additional keying material derived between EAP client and server that
   is exported by the EAP method is called Extended Master Session Key
   (EMSK).  EMSK is not used in session key derivation but it could be
   used for the needs of other applications in higher layer protocols.

   In the architecture introduced in Section 2.2 the node or router is
   the peer and the root is the authenticator.  When the supplicant and
   authenticator are one hop away the authenticator can be reached
   directly.  However, this is rarely the case.  In other cases the
   authenticator authenticates neighboring supplicants first.  The
   router nodes that are authenticated become relay authenticators in
   the next phase and they relay authentication messages from the
   supplicants to the authenticator and vice versa.  This continues
   until all nodes are authenticated.

   EAP is a lock-step protocol, i.e. it executes in pairs of EAP-Request
   messages sent by the server and EAP-Response messages sent by the
   peer.  At the end, the server indicates the status of authentication,
   usually by EAP-Success message which also carries the MSK.  The first
   EAP-Request/Response pair is used for the server to request the
   identity and the peer to provide it.  In the other pairs of EAP
   exchanges EAP method is executed.

   Several EAP methods have been standardized each for different
   purposes.  To authenticate devices with certificates, EAP Transport
   Layer Security (TLS) v1.2 specified in [RFC5216] which supports
   certificate-based mutual authentication is used.

   Smart Energy Profile 2.0 Application Protocol Specification [SE2.0]



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   mandates each device to be factory programmed with a certificate.
   The certificate is bound to a unique network ID, e.g. the device's
   MAC address or EUI-64 address.  During EAP-Identity exchange the EAP
   peer provides its EUI-64 address as an identity to EAP server.  This
   enables the server to validate the device certificate.

5.3.  PANA

   PANA (Protocol for carrying Authentication for Network Access)
   [RFC5191] defines an EAP transport over UDP where a PANA Client (PaC)
   is an EAP peer and a PANA Authentication Agent (PAA) is an EAP
   authenticator.  There are three bootstrapping scenarios using PANA.

   1.  Use of PANA for bootstrapping link-layer security.

       In this case, PANA is used for network access authentication to
       bootstrap link-layer ciphering.  Security for higher-layer (i.e.,
       IP layer and above) protocols is bootstrapped from an IB or OOB
       mechanism other than PANA.  For example, in a 6LoWPAN deployment
       PANA authentication can take place to bootstrap IEEE 802.15.4 MAC
       layer ciphering keys.  In ZigBee IP, IEEE 802.15.4 MAC layer
       ciphering keys used as session keys are derived from a group key
       so called a Network Key that is securely distributed to each
       joining node upon successful PANA authentication using AES key
       wrap over PANA [I-D.ohba-pana-keywrap] where the key encryption
       key is derived from the EAP MSK (Master Session Key) [RFC3748].

   2.  Use of PANA for bootstrapping higher-layer security.

       In this scenario, PANA is used as an OOB mechanism for higher-
       layer authentication to bootstrap ciphering keys for one or more
       higher-layer protocols independently of network access
       authentication.  The PAA may reside in a higher-layer network
       element such as an ANSI C12.22 authentication host [C1222] and a
       CoAP server, or an independent server dedicated for service
       authentication for multiple higher-layer protocols.  When
       bootstrapping ANSI C12.22 security for which no IB key management
       mechanism is available, ANSI C12.22 ciphering keys are directly
       derived from EAP key material established from PANA
       authentication.  When bootstrapping CoAP security with DTLS
       protection, a PSK (Pre-Shared Key) credential in the combined
       usage of DTLS (Datagram Transport Layer Security) [RFC4347] and
       PSK mode of TLS [RFC4279] is derived from EAP key material and
       DTLS ciphering keys are generated as a result of a successful
       DTLS handshake.  Similarly, when bootstrapping CoAP security with
       IPsec ESP protection, a PSK credential of IKEv2 [RFC5996] is
       derived from EAP key material and IPsec ESP ciphering keys are
       generated as a result of a successful IKEv2 handshake.



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       The ability to bootstrap multiple higher-layer protocols from a
       single execution of PANA authentication is important to save the
       computational resources for resource-constrained devices
       especially where public-key based authentication is used.

   3.  Use of PANA for bootstrapping both link-layer and higher-layer
       security.

       This case is the combination of the other two cases, and the most
       optimized way for bootstrapping resource-constrained devices.
       This case is only applicable where both the network access
       authentication and the higher-layer authentication use the same
       authentication server with the same authentication credentials.

   The second and third scenarios are generally referred to as Single
   Sign-On in section 4.2.2.2 of [NISTIR7628VOL1], where the root keys
   for higher-layer protocols can be derived from EAP EMSK (Extended
   Master Session Key) as an USRK (Usage-Specific Root Key) [RFC5295].

   A PANA Relay Element (PRE) is needed to enable PANA messaging between
   a PANA Client (PaC) which is the node to be authenticated and a PANA
   Authentication Agent (PAA) which is the authenticator where the two
   nodes cannot reach each other by means of regular IP routing.  This
   happens during authentication since only a link-local IPv6 address
   can be used prior to the completion of a succesful authentication.

   PRE which is one hop away from PaC receives PANA messages and relays
   the message contents (payload) by encapsulating it in a message
   parameter called Attribute Value Pair (AVP).  PRE also needs to send
   header contents such as PaC's IP address and UDP port number in a
   different AVP.  PRE has IP routing established with PAA which could
   be several hops away.  PAA sends its reply messages in which the
   payload is encapsulated in an AVP.  It also adds the AVP containing
   PaC's IP address and UDP port number.  PRE sends creates a link local
   PDU using these AVPs and sends it to PaC.

   The requirements for the use of PANA as a bootsrapping protocol can
   be stated as follows:

   o  A new entity called PANA Relay Element needs to be added to the
      PANA architecture.  Behaviour of PANA Relay Element needs to be
      defined.

   o  New AVPs needed for PANA Relay Element operation for properly
      relaying messages from the client to the authenticator and vice
      versa are required to be specified.





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   o  An extension to PANA to securely distribute keys from the PANA
      Authentication Agent to the PANA Client using AES Key Wrap with
      Padding algorithm needs to be defined.  This is needed in order to
      use PANA for group key distribution.

5.4.  HIP-DEX

   [RFC4423] introduces the Host Identity Protocol (HIP) where the Host
   Identity (HI) is a Cryptographic key (RSA, DSA, or ECC).  A 128-bit
   length Host Identity Tag (HIT) is derived from the HI (hashed) and
   functions as an IPv6 address (/128 prefix) for applications.  A four-
   packet Peer-to-Peer Host Identity Protocol Base EXchange (HIP BEX)
   establishes a security association (SA, similar to IKE), indexed by
   the HITs, but independent of the IP address.  So HIP can be
   considered as a shim layer between the transport(TCP/UDP) and IP,
   providing authentication, data confidentiality, mobility in one
   basket.

   The HIP-BEX involves many crypto primitives that are difficult to run
   on constrained nodes.  HIP Diet Exchange (HIP-DEX)
   [I-D.moskowitz-hip-rg-dex] is a way to make HIP lightweight.
   Basically, HIP-DEX a variant of the HIP-BEX specifically designed to
   use as few crypto primitives as possible yet still provide the same
   class of security features as HIP-BEX.

   HIP-DEX can be used for mutual authentication between two endpoints.
   After mutual authentication, the two endpints establish a shared
   secret, which is fresh and fed into the encryption algorithm for data
   confidentiality.  So HIP-DEX can achieve the authentication, key
   freshness and data confidentiality objectives of security
   bootstrapping.

   When a node wants to authenticate to the network using HIP and Diet-
   HIP, it should be able to complete the HIP-BEX or HIP-DEX with the
   trust anchor or some delegate.  In HIP, it does not matter how many
   domains, and nodes can authenticate each other as long as they have
   the secret.

   In the architecture introduced in Section 2.2 the node and router
   could be the HIP end-points.  Depending on who initiates the HIP Diet
   Exchange, the node or router could act as the HIP initiator and HIP
   responder respectively.  And the initiator and responder can be
   multiple hops way from each other, as long as there is an IP
   connectivity between them.

   An important requirement for the HIP-DEX to work in the architecture,
   the initiator should be able to get the IP address of the responder,
   either using DNS infrastructure or local configuration.



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5.5.  802.1X

   IEEE 802.1X defines how EAP packets can be transported over in Layer
   2, i.e.  Ethernet frames [802.1x] by encapsulating EAP packets into
   EAP Over Lan (EAPOL) frames between EAP peer, called supplicant and
   the authenticator.  EAPOL can also be used in 802.11 wireless links.

   To enable IEEE 802.15.4 devices to use EAP authentication, EAP
   packets encapsulated in EAPOL frames can be carried as payload in
   802.15.4 data frames [802.15.4].  EAPOL is well defined and widely
   used and it lends itself to be easily carried in 802.15.4 data
   frames.  For this, Frame Type subfield of the Frame Control Field of
   IEEE 802.15.4 MAC header needs to be set to a special value to
   indicate the type of the payload, i.e. 802.1X encapsulated EAP
   packets.  EAPOL packets are encoded following common EAPOL PDU
   structure defined in [802.1x] into the data payload field of 802.15.4
   data frames.

   Authentication proceeds as follows: authenticator authenticates the
   supplicants that are on the next hop first.  This enables a secure
   link between the authenticator and these first-hop nodes.  First-hop
   nodes or router become Relay Authenticators in the next phase of
   authentication.  Relay authenticators tunnel EAPOL frames to the
   authenticator in the secure link established.  This way all the
   supplicants are gradually authenticated.

   The keys established from a successful EAP method (such as PSK mode
   of TLS), the node runs neighbor discovery protocol to get an IPv6
   address assigned [I-D.ietf-6lowpan-nd].  Data transfer can be secured
   using DTLS or IPSec.  Keys derived from EAP TLS are used in either
   generating DTLS ciphering keys after a successful DTLS handshake or
   IPSec ESP ciphering keys after a successful IKEv2 handshake.

   802.1X can achieve the authentication, key freshness and data
   confidentiality objectives of security bootstrapping.  Multi domain
   operation is intrinsically supported due to the use of EAP and AAA.

   The requirements for the use of 802.1X defined EAPOL as a
   bootsrapping protocol can be stated as follows:

   o  A special value in the Frame Type subfield of the Frame Control
      Field of IEEE 802.15.4 MAC header to indicate the type of the
      payload,

   o  Group addresses for 802.15.4 corresponding to EAPOL Group Address
      Assignments defined in Table 11.1 of [802.1x], especially to be
      used in EAPOL-Start packet.




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   o  Which MAC frames of beacon, data, acknowledgment and MAC command
      as defined in [802.15.4] with what security levels are mapped to
      controlled port, which MAC frames with what security levels are
      mapped to uncontrolled port and which MAC frames are never mapped
      to any of controlled/uncontrolled port (i.e., the payload of those
      frames are used by the MAC-ayer ieself and never used by upper
      layers).


6.  Security Considerations

   TBD.


7.  IANA Considerations

   This memo includes no request to IANA.


8.  Acknowledgements

   Thanks to Zach Shelby for editing, comments, and overall assistance.
   Special thanks also to Rene Struik and Carsten Borman for their
   comments that helped us improve the writing.


9.  References

9.1.  Normative References

   [802.15.4]
              IEEE Std 802.15.4-2006, "Wireless Medium Access Control
              (MAC) and Physical Layer (PHY) Specifications for Low Rate
              Wireless Personal Area Networks (WPANs)", September 2006.

   [802.1x]   IEEE Std 802.1X-2010, "IEEE 802.1X Port-Based Network
              Access Control", February 2010.

   [RF4CE]    ZigBee Alliance, "Zigbee RF4CE Specification Version
              1.00", March 2009.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, "Extensible Authentication Protocol (EAP)",
              RFC 3748, June 2004.




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   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals",
              RFC 4919, August 2007.

   [RFC5191]  Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
              Yegin, "Protocol for Carrying Authentication for Network
              Access (PANA)", RFC 5191, May 2008.

   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
              Authentication Protocol", RFC 5216, March 2008.

   [RFC5548]  Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
              "Routing Requirements for Urban Low-Power and Lossy
              Networks", RFC 5548, May 2009.

   [RFC5673]  Pister, K., Thubert, P., Dwars, S., and T. Phinney,
              "Industrial Routing Requirements in Low-Power and Lossy
              Networks", RFC 5673, October 2009.

   [ROMER04]  Romer, K. and F. Mattern, "The design space of wireless
              sensor networks", IEEE Wireless Communications, vol. 11,
              no. 6, pp. 54-61, December 2004.

   [SE2.0]    ZigBee Alliance, "Smart Energy Profile 2.0 Technical
              Requirements Document", April 2010.

9.2.  Informative References

   [C1222]    American National Standard, "Protocol Specification For
              Interfacing to Data Communication Networks", ANSI C12.22-
              2008, 2008.

   [I-D.ietf-6lowpan-nd]
              Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor
              Discovery Optimization for Low-power and Lossy Networks",
              draft-ietf-6lowpan-nd-14 (work in progress), October 2010.

   [I-D.ietf-core-coap]
              Shelby, Z., Frank, B., and D. Sturek, "Constrained
              Application Protocol (CoAP)", draft-ietf-core-coap-03
              (work in progress), October 2010.

   [I-D.ietf-roll-rpl]
              Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., and J.
              Vasseur, "RPL: IPv6 Routing Protocol for Low power and
              Lossy Networks", draft-ietf-roll-rpl-15 (work in



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              progress), November 2010.

   [I-D.moskowitz-hip-rg-dex]
              Moskowitz, R., "HIP Diet EXchange (DEX)",
              draft-moskowitz-hip-rg-dex-02 (work in progress),
              July 2010.

   [I-D.narten-iana-considerations-rfc2434bis]
              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs",
              draft-narten-iana-considerations-rfc2434bis-09 (work in
              progress), March 2008.

   [I-D.ohba-pana-keywrap]
              Chakrabarti, S., Cragie, R., Duffy, P., Ohba, Y., and A.
              Yegin, "Protocol for Carrying Authentication for Network
              Access (PANA) Extension for Key Wrap",
              draft-ohba-pana-keywrap-01 (work in progress),
              October 2010.

   [NISTIR7628VOL1]
              The Smart Grid Interoperability Panel -  Cyber Security
              Working Group, "Guidelines for Smart Grid Cyber Security:
              Vol. 1,  Smart Grid Cyber Security Strategy, Architecture,
              and High-Level Requirements", NISTIR 7628, vol. 1, 2010.

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              July 2003.

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4279]  Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
              for Transport Layer Security (TLS)", RFC 4279,
              December 2005.

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, April 2006.

   [RFC4423]  Moskowitz, R. and P. Nikander, "Host Identity Protocol
              (HIP) Architecture", RFC 4423, May 2006.



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   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5247]  Aboba, B., Simon, D., and P. Eronen, "Extensible
              Authentication Protocol (EAP) Key Management Framework",
              RFC 5247, August 2008.

   [RFC5295]  Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri,
              "Specification for the Derivation of Root Keys from an
              Extended Master Session Key (EMSK)", RFC 5295,
              August 2008.

   [RFC5433]  Clancy, T. and H. Tschofenig, "Extensible Authentication
              Protocol - Generalized Pre-Shared Key (EAP-GPSK) Method",
              RFC 5433, February 2009.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, September 2010.


Appendix A.  Examples of Node Configuration

   Before any detail on methods is explored, the following section will
   provide various examples this document could cover.  Exact
   requirements will be brought forward in subsequent sections.  For the
   reader's general understanding this section is placed to give an idea
   of an acceptable usage scenario.

A.1.  Smart Energy

A.1.1.  Initial Meter Installation

   The meter is initially loaded with code and network keys through a
   physical interface at the factory.  The meter is installed at a
   customers home, and configured by the installer through the backbone
   link (via GSM modem, etc).  Both operations can be performed through
   methods defined herein.

A.1.2.  Home Expansions

   The user wishes to join a thermostat onto the network.  They press a
   button on the thermostat, which enters join mode.  They press a
   button on the smart meter, which allows nodes to join the network.
   The devices both have displays, so they display a certain number
   which the user verifies match on both devices.  The thermostat has
   now securely joined the network.




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A.2.  Consumer Products

A.2.1.  Connecting DVD Remote to DVD Player

   The user pushes a join button on the DVD remote and DVD player.  The
   devices find each other, and blink in unison to indicate to the user
   which two devices will join.  The user presses the button to confirm
   this, and the two devices are now joined together.

A.2.2.  Adding a TV to a network with a DVD player and remote

   The user then presses the join button on the DVD player and TV.  The
   devices again find each other and blink in unison, with the addition
   that the remote control also blinks to indicate it is present in the
   network.

A.2.3.  Providing GPS Location Data

   A user has a simple GPS receiver (that has no user interface) they
   wish to broadcast location data with.  The user switches on their
   camera, and enters a PIN from the base of the GPS.  The user can now
   view GPS information such as satellite health from their camera.  In
   addition photos are automatically tagged with location information.

A.3.  Commercial Building Automation

A.3.1.  Light Installation

   The electrician installs the light fixture.  Each light has a barcode
   printed on it.  They use a handheld barcode scanner tool, which acts
   as the commissioning tool.  When they scan a barcode with the tool,
   the tool asks the electrician to enter some additional information
   such as light fixture location.  The tool securely registers the
   light fixture on the network, along with setting parameters inside
   the light fixture.


Appendix B.  Example Exchanges

   The following details how the protocol handles certain conditions and
   situations through examples.  Note that each example is a more
   detailed description of the examples in Appendix A.

B.1.  Smart Energy: Meter Manufacture

B.2.  Smart Energy: Meter Installation





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B.3.  Smart Energy: Home Expansion

B.4.  Consumer: Connecting DVD Remote to DVD Player

                     Supported User Interface Profiles

             +----------------+------------+----------------+
             |     Profile    | DVD Player | Remote Control |
             +----------------+------------+----------------+
             |      none      |      Y     |        Y       |
             |     simple     |      Y     |        Y       |
             |    numerical   |      Y     |        N       |
             | alphanumerical |      Y     |        N       |
             |    Graphical   |      Y     |        N       |
             +----------------+------------+----------------+

                   Supported Bootstrap Transport Layers

                +----------+------------+----------------+
                |   Layer  | DVD Player | Remote Control |
                +----------+------------+----------------+
                | Physical |      Y     |        Y       |
                | 802.15.4 |      Y     |        Y       |
                |   IrDA   |      Y     |        N       |
                +----------+------------+----------------+

                        Supported Security Methods

            +------------------+------------+----------------+
            |      Method      | DVD Player | Remote Control |
            +------------------+------------+----------------+
            |       None       |      Y     |        Y       |
            |        EAP       |      Y     |        N       |
            | Asymmetric, User |      Y     |        Y       |
            |  Asymmetric, CA  |      Y     |        N       |
            +------------------+------------+----------------+

   The DVD player and remote control have a number of ways in which they
   could be joined together.  The remote control does not have any
   unique identifier printed on it, thus no pre-shared key can be
   identified.  This leaves either an unsecure joining method, or some
   asymmetric security method.

   The remote control has a button on it for 'join', as does the DVD
   player.  The user pushes the button on the DVD player, and then
   pushes the button on the remote control.  Based on the UI profile,
   this causes the following to occur:




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   o  DVD Player scans for existing network in advertise mode.  Finding
      none, it starts a new network and that network enters advertise
      mode.

   o  The DVD remote scans for a network, and then finds the DVD
      player's network.

   o  The devices generate a shared secret (ie: Diffie-Hellman), and
      both blink their LED in a unique pattern based on this shared
      secret.

   o  The user user confirms both devices are blinking the same pattern,
      as both LEDs are blinking in unison.

   o  The DVD player displays 'JOIN OK' on it's LCD panel.

B.5.  Consumer: Adding a TV to a network with a DVD player and remote

   This network will have three devices: a TV, a DVD Player, and a
   Remote Control.  The user will run the bootstrap protocol between the
   TV and Remote Control in this example, although it could also be run
   between the TV and DVD player.

                     Supported User Interface Profiles

                 +----------------+----+----------------+
                 |     Profile    | TV | Remote Control |
                 +----------------+----+----------------+
                 |      none      |  Y |        Y       |
                 |     simple     |  Y |        Y       |
                 |    numerical   |  Y |        N       |
                 | alphanumerical |  Y |        N       |
                 |    Graphical   |  Y |        N       |
                 +----------------+----+----------------+

                   Supported Bootstrap Transport Layers

                    +----------+----+----------------+
                    |   Layer  | TV | Remote Control |
                    +----------+----+----------------+
                    | Physical |  Y |        Y       |
                    | 802.15.4 |  Y |        Y       |
                    |   IrDA   |  Y |        N       |
                    +----------+----+----------------+







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                        Supported Security Methods

                +------------------+----+----------------+
                |      Method      | TV | Remote Control |
                +------------------+----+----------------+
                |       None       |  Y |        Y       |
                |     EAP-GPSK     |  Y |        N       |
                | Asymmetric, User |  Y |        Y       |
                |  Asymmetric, CA  |  Y |        N       |
                +------------------+----+----------------+

   The TV and remote control have a number of ways in which they could
   be joined together.  The remote control does not have any unique
   identifier printed on it, thus no pre-shared key can be identified.
   This leaves either an unsecure joining method, or some asymmetric
   security method.

   The remote control has a button on it for 'join', as does the TV.  In
   this example two sequence will be considered: where the TV button is
   pressed first, and where the remote control button is pressed first.

   If the TV join button is pressed first:

   o  TV scans for existing networks in advertise mode.  Finding none,
      it starts a new network and that network enters advertise mode.

   o  The remote scans for a network, and then finds the TV's network.

   o  The remote informs the TV it is on an existing network, and thus
      will require the TV to join this network.

   o  The devices generate a shared secret, and both blink their LED in
      a unique pattern.

   o  The DVD player in addition blinks, so the user is informed that if
      they confirm the join action the resulting network will have all
      three devices in it.

   o  The user confirms both devices are blinking the same pattern, as
      both LEDs are blinking in unison.

   o  The TV displays 'JOIN OK' onscreen, along with any information
      about the network it just joined.

   If the remote control join button is pressed first:

   o  Remote control scans for existing networks in advertise mode.
      Finding none, it advertises it's network.



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   o  The TV scans for a network, and then finds the remote control's
      network.

   o  The devices generate a shared secret, and both blink their LED in
      a unique pattern.

   o  The DVD player in addition blinks, so the user is informed that if
      they confirm the join action the resulting network will have all
      three devices in it.

   o  The user confirms both devices are blinking the same pattern, as
      both LEDs are blinking in unison.

   o  The TV displays 'JOIN OK' onscreen, along with any information
      about the network it just joined.

B.6.  Consumer: Providing GPS Location Data

B.7.  Commercial: Building Automation


Authors' Addresses

   Behcet Sarikaya
   Huawei USA
   1700 Alma Dr. Suite 500
   Plano, TX  75075

   Email: sarikaya@ieee.org


   Yoshihiro Ohba
   Toshiba
   Tokyo, Japan

   Email: yoshihiro.ohba@toshiba.co.jp


   Zhen Cao
   China Mobile
   Beijing, China

   Email: caozhen@chinamobile.com








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   Robert Cragie
   Pacific Gas and Electric
   89 Greenfield Crescent
   Wakefield, UK  WF4 4WA

   Email: robert.cragie@gridmerge.com













































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