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Network Working Group                                  O. Garcia-Morchon
Internet-Draft                                                  S. Kumar
Intended status: Informational                          Philips Research
Expires: April 12, 2017                                         M. Sethi
                                                                Ericsson


                                                        October 09, 2016


       Security Considerations in the IP-based Internet of Things
                      draft-irtf-t2trg-iot-seccons-00

Abstract

   A direct interpretation of the Internet of Things concept refers to
   the usage of standard Internet protocols to allow for human-to-thing
   or thing-to-thing communication.  Although the security needs are
   well-recognized, it is still not fully clear how existing IP-based
   security protocols can be applied to this new setting.  This
   Internet-Draft first provides an overview of security architecture,
   its deployment model and general security needs in the context of the
   lifecycle of a thing.  Then, it presents challenges and requirements
   for the successful roll-out of new applications and usage of standard
   IP-based security protocols when applied to get a functional 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).  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/.

   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
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 12, 2017.








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Copyright Notice

   Copyright (c) 2016 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 Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Conventions and Terminology Used in this Document . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The Thing Lifecycle and Architectural Considerations  . . . .   4
     3.1.  Threat Analysis . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Security Aspects  . . . . . . . . . . . . . . . . . . . .   9
   4.  State of the Art  . . . . . . . . . . . . . . . . . . . . . .  12
     4.1.  IP-based Security Solutions . . . . . . . . . . . . . . .  12
   5.  Security Levels for the IP-based Internet of Things . . . . .  14
     5.1.  Security Architecture . . . . . . . . . . . . . . . . . .  18
     5.2.  Security Model  . . . . . . . . . . . . . . . . . . . . .  19
     5.3.  Security Bootstrapping and Management . . . . . . . . . .  20
     5.4.  Network Security  . . . . . . . . . . . . . . . . . . . .  22
     5.5.  Application Security  . . . . . . . . . . . . . . . . . .  23
   6.  Challenges and Security Considerations for a Secure Internet
       of Things . . . . . . . . . . . . . . . . . . . . . . . . . .  25
     6.1.  Constraints and Heterogeneous Communication . . . . . . .  25
       6.1.1.  Tight Resource Constraints  . . . . . . . . . . . . .  25
       6.1.2.  Denial-of-Service Resistance  . . . . . . . . . . . .  26
       6.1.3.  Protocol Translation and End-to-End Security  . . . .  27
     6.2.  Bootstrapping of a Security Domain  . . . . . . . . . . .  28
     6.3.  Operation . . . . . . . . . . . . . . . . . . . . . . . .  28
       6.3.1.  End-to-End Security . . . . . . . . . . . . . . . . .  29
       6.3.2.  Group Membership and Security . . . . . . . . . . . .  29
       6.3.3.  Mobility and IP Network Dynamics  . . . . . . . . . .  30
     6.4.  Software update . . . . . . . . . . . . . . . . . . . . .  30
     6.5.  Verifying device behavior . . . . . . . . . . . . . . . .  31
     6.6.  End-of-life . . . . . . . . . . . . . . . . . . . . . . .  32
     6.7.  Penetration testing . . . . . . . . . . . . . . . . . . .  32
     6.8.  Quantum-resistance  . . . . . . . . . . . . . . . . . . .  32
   7.  Next Steps towards a Flexible and Secure Internet of Things .  33
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  33



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   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  33
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  34
   11. Informative References  . . . . . . . . . . . . . . . . . . .  34
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  40

1.  Conventions and Terminology 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 "Key words for use in
   RFCs to Indicate Requirement Levels" [RFC2119].

2.  Introduction

   The Internet of Things (IoT) denotes the interconnection of highly
   heterogeneous networked entities and networks following a number of
   communication patterns such as: human-to-human (H2H), human-to-thing
   (H2T), thing-to-thing (T2T), or thing-to-things (T2Ts).  The term IoT
   was first coined by the Auto-ID center [AUTO-ID] in 1999.  Since
   then, the development of the underlying concepts has ever increased
   its pace.  Nowadays, the IoT presents a strong focus of research with
   various initiatives working on the (re)design, application, and usage
   of standard Internet technology in the IoT.

   The introduction of IPv6 and web services as fundamental building
   blocks for IoT applications [RFC6568] promises to bring a number of
   basic advantages including: (i) a homogeneous protocol ecosystem that
   allows simple integration with Internet hosts; (ii) simplified
   development of very different appliances; (iii) an unified interface
   for applications, removing the need for application-level proxies.
   Such features greatly simplify the deployment of the envisioned
   scenarios ranging from building automation to production environments
   to personal area networks, in which very different things such as a
   temperature sensor, a luminaire, or an RFID tag might interact with
   each other, with a human carrying a smart phone, or with backend
   services.

   This Internet Draft presents an overview of the security aspects of
   the envisioned all-IP architecture as well as of the lifecycle of an
   IoT device, a thing, within this architecture.  In particular, we
   review the most pressing aspects and functionalities that are
   required for a secure all-IP solution.

   With this, this Internet-Draft pursues several goals.  First, we aim
   at presenting a comprehensive view of the interactions and
   relationships between an IoT application and security.  Second, we
   aim at describing challenges for a secure IoT in the specific context
   of the lifecycle of a resource-constrained device.  The final goal of



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   this draft is to discuss the security considerations that need to be
   taken into consideration towards a secure IoT.

   The rest of the Internet-Draft is organized as follows.  Section 3
   depicts the lifecycle of a thing and gives general definitions for
   the main security aspects within the IoT domain.  In Section 4, we
   review existing protocols and work done in the area of security for
   wireless sensor networks.  Section 5 identifies general challenges
   and needs for an IoT security protocol design and discusses existing
   protocols and protocol proposals against the identified requirements.
   Section 6 proposes a number of illustrative security suites
   describing how different applications involve distinct security
   needs.  Section 7 includes final remarks and conclusions.

3.  The Thing Lifecycle and Architectural Considerations

   We consider the installation of a Building Automation and Control
   (BAC) system to illustrate the lifecycle of a thing but can be
   similarly extended to other scenarios.  A BAC system consists of a
   network of interconnected nodes that perform various functions in the
   domains of HVAC (Heating, Ventilating, and Air Conditioning),
   lighting, safety etc.  The nodes vary in functionality and a majority
   of them represent resource constrained devices such as sensors and
   luminaries.  Some devices may also be battery operated or battery-
   less nodes, demanding for a focus on low energy consumption and on
   sleeping devices.

   In our example, the life of a thing starts when it is manufactured.
   Due to the different application areas (i.e., HVAC, lighting, safety)
   nodes are tailored to a specific task.  It is therefore unlikely that
   one single manufacturer will create all nodes in a building.  Hence,
   interoperability as well as trust bootstrapping between nodes of
   different vendors is important.  The thing is later installed and
   commissioned within a network by an installer during the
   bootstrapping phase.  Specifically, the device identity and the
   secret keys used during normal operation are provided to the device
   during this phase.  Different subcontractors may install different
   IoT devices for different purposes.  Furthermore, the installation
   and bootstrapping procedures may not be a defined event but may
   stretch over an extended period of time.  After being bootstrapped,
   the device and the system of things are in operational mode and run
   the functions of the BAC system.  During this operational phase, the
   device is under the control of the system owner.  For devices with
   lifetimes spanning several years, occasional maintenance cycles may
   be required.  During each maintenance phase, the software on the
   device can be upgraded or applications running on the device can be
   reconfigured.  The maintenance tasks can thereby be performed either
   locally or from a backend system.  Depending on the operational



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   changes of the device, it may be required to re-bootstrap at the end
   of a maintenance cycle.  The device continues to loop through the
   operational phase and the eventual maintenance phase until the device
   is decommissioned at the end of its lifecycle.  However, the end-of-
   life of a device does not necessarily mean that it is defective but
   rather denotes a need to replace and upgrade the network to next-
   generation devices in order to provide additional functionality.
   Therefore the device can be removed and re-commissioned to be used in
   a different network under a different owner by starting the lifecycle
   over again.  Figure 1 shows the generic lifecycle of a thing.  This
   generic lifecycle is also applicable for various IoT scenarios other
   than BAC systems.

   More recently building control networks employ IP-based standards
   allowing seamless control over the various nodes with a single
   management system.  While allowing for easier integration, this shift
   towards IP-based standards results in new requirements regarding the
   implementation of IP security protocols on constrained devices and
   the bootstrapping of security keys for devices across multiple
   manufacturers.

    _Manufactured           _SW update          _Decommissioned
   /                       /                   /
   |   _Installed          |   _ Application   |   _Removed &
   |  /                    |  / reconfigured   |  /  replaced
   |  |   _Commissioned    |  |                |  |
   |  |  /                 |  |                |  |   _Reownership &
   |  |  |    _Application |  |   _Application |  |  / recommissioned
   |  |  |   /   running   |  |  / running     |  |  |
   |  |  |   |             |  |  |             |  |  |             \\
   +##+##+###+#############+##+##+#############+##+##+##############>>>
       \/  \______________/ \/  \_____________/ \___/         time //
       /           /         \          \          \
   Bootstrapping  /      Maintenance &   \     Maintenance &
                 /      re-bootstrapping  \   re-bootstrapping
           Operational                Operational

       Figure 1: The lifecycle of a thing in the Internet of Things.

3.1.  Threat Analysis

   This section explores the security threats and vulnerabilities of a
   network of things in the IoTs.  Security threats have been analyzed
   in related IP protocols including HTTPS [RFC2818], COAP[RFC7252]
   6LoWPAN [RFC4919], ANCP [RFC5713], DNS security threats [RFC3833],
   SIP [RFC3261], IPv6 ND [RFC3756], and PANA [RFC4016].  Nonetheless,
   the challenge is about their impacts on scenarios of the IoTs.  In
   this section, we specifically discuss the threats that could



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   compromise an individual thing, or network as a whole, with regard to
   different phases in the thing's lifecycle.  Note that these set of
   threats might go beyond the scope of Internet protocols but we gather
   them here for the sake of completeness.

   1.  Cloning of things: During the manufacturing process of a thing,
       an untrusted manufacturer can easily clone the physical
       characteristics, firmware/software, or security configuration of
       the thing.  Subsequently, such a cloned thing may be sold at a
       cheaper price in the market, and yet be still able to function
       normally, as a genuine thing.  For example, two cloned devices
       can still be associated and work with each other.  In the worst
       case scenario, a cloned device can be used to control a genuine
       device.  One should note here, that an untrusted manufacturer may
       also change functionality of the cloned thing, resulting in
       degraded functionality with respect to the genuine thing
       (thereby, inflicting potential reputational risk to the original
       thing manufacturer).  Moreover, it can implement additional
       functionality with the cloned thing, such as a backdoor.

   2.  Malicious substitution of things: During the installation of a
       thing, a genuine thing may be substituted with a similar variant
       of lower quality without being detected.  The main motivation may
       be cost savings, where the installation of lower-quality things
       (e.g., non-certified products) may significantly reduce the
       installation and operational costs.  The installers can
       subsequently resell the genuine things in order to gain further
       financial benefits.  Another motivation may be to inflict
       reputational damage on a competitor's offerings.

   3.  Eavesdropping attack: During the commissioning of a thing into a
       network, it may be susceptible to eavesdropping, especially if
       operational keying materials, security parameters, or
       configuration settings, are exchanged in clear using a wireless
       medium.  After obtaining the keying material, the attacker might
       be able to recover the secret keys established between the
       communicating entities (e.g., H2T, T2Ts, or Thing to the backend
       management system), thereby compromising the authenticity and
       confidentiality of the communication channel, as well as the
       authenticity of commands and other traffic exchanged over this
       communication channel.  When the network is in operation, T2T
       communication may be eavesdropped upon if the communication
       channel is not sufficiently protected or in the event of session
       key compromise due to a long period of usage without key renewal
       or updates.

   4.  Man-in-the-middle attack: Both the commissioning phase and
       operational phases may also be vulnerable to man-in-the-middle



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       attacks, e.g., when keying material between communicating
       entities is exchanged in the clear and the security of the key
       establishment protocol depends on the tacit assumption that no
       third party is able to eavesdrop on or sit in between the two
       communicating entities during the execution of this protocol.
       Additionally, device authentication or device authorization may
       be nontrivial, or may need support of a human decision process,
       since things usually do not have a priori knowledge about each
       other and can, therefore, not always be able to differentiate
       friends and foes via completely automated mechanisms.  Thus, even
       if the key establishment protocol provides cryptographic device
       authentication, this knowledge on device identities may still
       need complementing with a human-assisted authorization step
       (thereby, presenting a weak link and offering the potential of
       man-in-the-middle attacks this way).

   5.  Firmware Replacement attack: When a thing is in operation or
       maintenance phase, its firmware or software may be updated to
       allow for new functionality or new features.  An attacker may be
       able to exploit such a firmware upgrade by replacing the thing's
       with malicious software, thereby influencing the operational
       behavior of the thing.  For example, an attacker could add a
       piece of malicious code to the firmware that will cause it to
       periodically report the energy usage of the lamp to a data
       repository for analysis.

   6.  Extraction of security parameters: A thing deployed in the
       ambient environment (such as sensors, actuators, etc.) is usually
       physically unprotected and could easily be captured by an
       attacker.  Such an attacker may then attempt to extract security
       information such as keys (e.g., device's key, private-key, group
       key) from this thing or try and re-program it to serve his needs.
       If a group key is used and compromised this way, the whole
       network may be compromised as well.  Compromise of a thing's
       unique key has less security impact, since only the communication
       channels of this particular thing in question are compromised.
       Here, one should caution that compromise of the communication
       channel may also compromise all data communicated over this
       channel.  In particular, one has to be weary of, e.g., compromise
       of group keys communicated over this channel (thus, leading to
       transitive exposure ripple effects).

   7.  Routing attack: As highlighted in [ID-Daniel], routing
       information in IoT can be spoofed, altered, or replayed, in order
       to create routing loops, attract/repel network traffic, extend/
       shorten source routes, etc.  Other relevant routing attacks
       include 1) Sinkhole attack (or blackhole attack), where an
       attacker declares himself to have a high-quality route/path to



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       the base station, thus allowing him to do anything to all packets
       passing through it. 2) Selective forwarding, where an attacker
       may selectively forward packets or simply drop a packet. 3)
       Wormhole attack, where an attacker may record packets at one
       location in the network and tunnel them to another location,
       thereby influencing perceived network behavior and potentially
       distorting statistics, thus greatly impacting the functionality
       of routing. 4) Sybil attack, whereby an attacker presents
       multiple identities to other things in the network.

   8.  Privacy threat: The tracking of a thing's location and usage may
       pose a privacy risk to its users.  An attacker can infer
       information based on the information gathered about individual
       things, thus deducing behavioral patterns of the user of interest
       to him.  Such information can subsequently be sold to interested
       parties for marketing purposes and targeted advertising.

   9.  Denial-of-Service attack: Typically, things have tight memory and
       limited computation, they are thus vulnerable to resource
       exhaustion attack.  Attackers can continuously send requests to
       be processed by specific things so as to deplete their resources.
       This is especially dangerous in the IoTs since an attacker might
       be located in the backend and target resource-constrained devices
       in an LLN.  Additionally, DoS attack can be launched by
       physically jamming the communication channel, thus breaking down
       the T2T communication channel.  Network availability can also be
       disrupted by flooding the network with a large number of packets.

   The following table summarizes the security threats we identified
   above and the potential point of vulnerabilities at different layers
   of the communication stack.  We also include related RFCs that
   include a threat model that might apply to the IoTs.



















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              +------------------+------------------+------------------+
              | Manufacturing    | Installation/    | Operation        |
              |                  | Commissioning    |                  |
 +------------+------------------+------------------+------------------+
 |Thing's     | Device Cloning   |Substitution      |Privacy threat    |
 |Model       |                  |ACE-OAuth(draft)  |Extraction of     |
 |            |                  |                  |security params   |
 +------------+------------------+------------------+------------------+
 |Application |                  |RFC2818, RFC7252  |RFC2818, Firmware |
 |Layer       |                  |OSCOAP(draft)     |replacement       |
 +------------+------------------+------------------+------------------+
 |Transport   |                  | Eavesdropping &  |Eavesdropping     |
 |Layer       |                  | Man-in-the-middle|Man-in-the-middle |
 +------------+------------------| attack, RFC7925  |------------------+
 |Network     |                  | RFC4919, RFC5713 |RFC4919,DoS attack|
 |Layer       |                  | RFC3833, RFC3756 |Routing attack    |
 |            |                  |                  |RFC3833           |
 +------------+------------------+------------------+------------------+
 |Physical    |                  |                  |DoS attack        |
 |Layer       |                  |                  |                  |
 +-------------------------------+------------------+------------------+

                  Figure 2: The security threat analysis

3.2.  Security Aspects

   The term security subsumes a wide range of different concepts.  In
   the first place, it refers to the basic provision of security
   services including confidentiality, authentication, integrity,
   authorization, non-repudiation, and availability, and some augmented
   services, such as duplicate detection and detection of stale packets
   (timeliness).  These security services can be implemented by a
   combination of cryptographic mechanisms, such as block ciphers, hash
   functions, or signature algorithms, and non-cryptographic mechanisms,
   which implement authorization and other security policy enforcement
   aspects.  For each of the cryptographic mechanisms, a solid key
   management infrastructure is fundamental to handling the required
   cryptographic keys, whereas for security policy enforcement, one
   needs to properly codify authorizations as a function of device roles
   and a security policy engine that implements these authorization
   checks and that can implement changes hereto throughout the system's
   lifecycle.

   In the context of the IoT, however, the security must not only focus
   on the required security services, but also how these are realized in
   the overall system and how the security functionalities are executed.
   To this end, we use the following terminology to analyze and classify
   security aspects in the IoT:



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   1.  The security architecture refers to the system elements involved
       in the management of the security relationships between things
       and the way these security interactions are handled (e.g.,
       centralized or distributed) during the lifecycle of a thing.

   2.  The security model of a node describes how the security
       parameters, processes, and applications are managed in a thing.
       This includes aspects such as process separation, secure storage
       of keying materials, etc.

   3.  Security bootstrapping denotes the process by which a thing
       securely joins the IoT at a given location and point in time.
       Bootstrapping includes the authentication and authorization of a
       device as well as the transfer of security parameters allowing
       for its trusted operation in a given network.

   4.  Network security describes the mechanisms applied within a
       network to ensure trusted operation of the IoT.  Specifically, it
       prevents attackers from endangering or modifying the expected
       operation of networked things.  Network security can include a
       number of mechanisms ranging from secure routing to data link
       layer and network layer security.

   5.  Object security describes mechanisms to allow transfer of secured
       blocks of data with end-to-end assurances independent of
       communication pattern, for e.g through proxies or other store-
       and-forward mechanisms.

   6.  Application security guarantees that only trusted instances of an
       application running in the IoT can communicate with each other,
       while illegitimate instances cannot interfere.




















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               ..........................
               :           +-----------+:
               :       *+*>|Application|*****
               :       *|  +-----------+:   *
               :       *|  +-----------+:   *
               :       *|->| Transport |:   *
               :    * _*|  +-----------+:   *
               :    *|  |  +-----------+:   *
               :    *|  |->|  Network  |:   *
               :    *|  |  +-----------+:   *
               :    *|  |  +-----------+:   *    *** Bootstrapping
               :    *|  +->|     L2    |:   *    ~~~ Transport Security
               :    *|     +-----------+:   *    ''' Object Security
               :+--------+              :   *
               :|Security| Configuration:   *
               :|Service |   Entity     :   *
               :+--------+              :   *
               :........................:   *
                                            *
   .........................                *  .........................
   :+--------+             :                *  :             +--------+:
   :|Security|   Node B    :                *  :   Node A    |Security|:
   :|Service |             :                *  :             |Service |:
   :+--------+             :                *  :             +--------+:
   :    |     +-----------+:                *  :+-----------+     |*   :
   :    |  +->|Application|:                ****|Application|<*+* |*   :
   :    |  |  +-----------+:''''''''''''''''''''+-----------+  |* |*   :
   :    |  |  +-----------+:                   :+-----------+  |* |*   :
   :    |  |->| Transport |~~~~~~~~~~~~~~~~~~~~~| Transport |<-|* |*   :
   :    |__|  +-----------+: ................. :+-----------+  |*_|*   :
   :       |  +-----------+: : +-----------+ : :+-----------+  | *     :
   :       |->|  Network  |: : |  Network  | : :|  Network  |<-|       :
   :       |  +-----------+: : +-----------+ : :+-----------+  |       :
   :       |  +-----------+: : +-----------+ : :+-----------+  |       :
   :       +->|     L2    |: : |     L2    | : :|     L2    |<-+       :
   :          +-----------+: : +-----------+ : :+-----------+          :
   :.......................: :...............: :.......................:
                      Overview of Security Mechanisms.

                                 Figure 3

   We now discuss an exemplary security architecture relying on a
   configuration entity for the management of the system with regard to
   the introduced security aspects (see Figure 2).  Inspired by the
   security framework for routing over low power and lossy network
   [ID-Tsao], we show an example of security model and illustrates how
   different security concepts and the lifecycle phases map to the
   Internet communication stack.  Assume a centralized architecture in



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   which a configuration entity stores and manages the identities of the
   things associated with the system along with their cryptographic
   keys.  During the bootstrapping phase, each thing executes the
   bootstrapping protocol with the configuration entity, thus obtaining
   the required device identities and the keying material.  The security
   service on a thing in turn stores the received keying material for
   the network layer and application security mechanisms for secure
   communication.  Things can then securely communicate with each other
   during their operational phase by means of the employed network and
   application security mechanisms.

4.  State of the Art

   Nowadays, there exists a multitude of control protocols for the IoT.
   For BAC systems, the ZigBee standard [ZB], BACNet [BACNET], or DALI
   [DALI] play key roles.  Recent trends, however, focus on an all-IP
   approach for system control.

   In this setting, a number of IETF working groups are designing new
   protocols for resource constrained networks of smart things.  The
   6LoWPAN working group [WG-6LoWPAN] concentrates on the definition of
   methods and protocols for the efficient transmission and adaptation
   of IPv6 packets over IEEE 802.15.4 networks [RFC4944].  The CoRE
   working group [WG-CoRE] provides a framework for resource-oriented
   applications intended to run on constrained IP network (6LoWPAN).
   One of its main tasks is the definition of a lightweight version of
   the HTTP protocol, the Constrained Application Protocol (CoAP)
   [RFC7252], that runs over UDP and enables efficient application-level
   communication for things.  Also IRTF groups are actively contributing
   to improve IoT security.

   Additionally industry alliances like Thread [Thread] are creating
   constrained IP protocol stacks based on the IETF work.

4.1.  IP-based Security Solutions

   In the context of the IP-based IoT solutions, consideration of TCP/IP
   security protocols is important as these protocols are designed to
   fit the IP network ideology and technology.  There are a wide range
   of specialized as well as general-purpose key exchange and security
   solutions exist for the Internet domain such as IKEv2/IPsec
   [RFC7296], TLS/SSL [RFC5246], DTLS [RFC5238], HIP [RFC7401], PANA
   [RFC5191], and EAP [RFC3748].  Some of these solutions are also been
   investigated now, such as, e.g., OSCOAP.  Figure 3 depicts the
   relationships between the discussed protocols in the context of the
   security terminology introduced in Section 3.1.





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             ..........................
             :           +-----------+:
             :       *+*>|Application|*****     *** Bootstrapping
             :       *|  +-----------+:   *     ### Transport Security
             :       *|  +-----------+:   *     === Network security
             :       *|->| Transport |:   *     ... Object security
             :    * _*|  +-----------+:   *
             :    *|  |  +-----------+:   *
             :    *|  |->|  Network  |:   *--> -PANA/EAP
             :    *|  |  +-----------+:   *    -HIP
             :    *|  |  +-----------+:   *
             :    *|  +->|     L2    |:   *     ## DTLS
             :    *|     +-----------+:   *     .. OSCOAP
             :+--------+              :   *
             :|Security| Configuration:   *     [] HIP,IKEv2
             :|Service |   Entity     :   *     [] ESP/AH
             :+--------+              :   *
             :........................:   *
                                          *
 .........................                *    .........................
 :+--------+             :                *    :             +--------+:
 :|Security|   Node B    :    Secure      *    :   Node A    |Security|:
 :|Service |             :    routing     *    :             |Service |:
 :+--------+             :   framework    *    :             +--------+:
 :    |     +-----------+:        |       **** :+-----------+     |*   :
 :    |  +->|Application|:........|............:|Application|<*+* |*   :
 :    |  |  +----##-----+:        |            :+----##-----+  |* |*   :
 :    |  |  +----##-----+:        |            :+----##-----+  |* |*   :
 :    |  |->| Transport |#########|#############| Transport |<-|* |*   :
 :    |__|  +----[]-----+:  ......|..........  :+----[]-----+  |*_|*   :
 :       |  +====[]=====+=====+===========+=====+====[]=====+  | *     :
 :       |->|| Network  |:  : |  Network  | :  :|  Network ||<-|       :
 :       |  +|----------+:  : +-----------+ :  :+----------|+  |       :
 :       |  +|----------+:  : +-----------+ :  :+----------|+  |       :
 :       +->||    L2    |:  : |     L2    | :  :|     L2   ||<-+       :
 :          +===========+=====+===========+=====+===========+          :
 :.......................:  :...............:  :.......................:
            Relationships between IP-based security protocols.

                                 Figure 4

   The Internet Key Exchange (IKEv2)/IPsec and the Host Identity
   protocol (HIP) reside at or above the network layer in the OSI model.
   Both protocols are able to perform an authenticated key exchange and
   set up the IPsec transforms for secure payload delivery.  Currently,
   there are also ongoing efforts to create a HIP variant coined Diet
   HIP [ID-HIP] that takes lossy low-power networks into account at the
   authentication and key exchange level.



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   Transport Layer Security (TLS) and its datagram-oriented variant DTLS
   secure transport-layer connections.  TLS provides security for TCP
   and requires a reliable transport, while DTLS secures and uses
   datagram-oriented protocols such as UDP.  Both protocols are
   intentionally kept similar and share the same ideology and cipher
   suites.

   The Extensible Authentication Protocol (EAP) is an authentication
   framework supporting multiple authentication methods.  EAP runs
   directly over the data link layer and, thus, does not require the
   deployment of IP.  It supports duplicate detection and
   retransmission, but does not allow for packet fragmentation.  The
   Protocol for Carrying Authentication for Network Access (PANA) is a
   network-layer transport for EAP that enables network access
   authentication between clients and the network infrastructure.  In
   EAP terms, PANA is a UDP-based EAP lower layer that runs between the
   EAP peer and the EAP authenticator.

   In addition, there is also new activities in IETF and W3C to define
   security protocols better tailored to IoT or for specific deployment
   situations.  The ACE WG is designing an authorization mechanism based
   on OAuth for constrained devices.  There is work on Object Security
   based CoAP protection mechanism being defined in OSCOAP. <<similar
   work in W3C - Oliver?>>

5.  Security Levels for the IP-based Internet of Things

   Different applications have different security requirements and needs
   and, depending on various factors, such as device capability,
   availability of network infrastructure, security services needed,
   usage, etc., the required security protection may vary from "simple
   security" to "full-blown security".  For example, applications may
   have different needs regarding authentication and confidentiality.
   While some application might not require any authentication at all,
   others might require strong end-to-end authentication.  In terms of
   secure bootstrapping of keys, some applications might assume the
   existence and online availability of a central key-distribution-
   center (KDC) within the 6LoWPAN network to distribute and manage
   keys; while other applications cannot rely on such a central party or
   their availability.

   Thus, it is essential to define security profiles to better tailor
   security solutions for different applications with the same
   characteristics and requirements.  This provides a means of grouping
   applications into profiles and then defines the minimal required
   security primitives to enable and support the security needs of the
   profile.  The security elements in a security profile can be
   classified according to Section 3.1, namely:



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   1 Security architecture,

   2 Security model,

   3 Security bootstrapping,

   4 Network security, and

   5 Application security.

   In order to (i) guide the design process by identifying open gaps;
   (ii) allow for later interoperability; and (iii) prevent possible
   security misconfigurations, this section defines a number of generic
   security profiles with different security needs.  Each security
   profile is identified by:

   1.  a short description,

   2.  an exemplary application that might use/require such a security
       policy,

   3.  the security requirements for each of the above security aspects
       according to our classification in Section 3.1.

   These security profiles can serve to guide the standardization
   process, since these explicitly describe the basic functionalities
   and protocols required to get different use cases up and running.  It
   can allow for later interoperability since different manufacturers
   can describe the implemented security profile in their products.
   Finally, the security profiles can avoid possible security
   misconfigurations, since each security profile can be bound to a
   different application area so that it can be clearly defined which
   security protocols and approaches can be applied where and under
   which circumstances.

   Note that each of these security profiles aim at summarizing the
   required security requirements for different applications and at
   providing a set of initial security features.  In other words, these
   profiles reflect the need for different security configurations,
   depending on the threat and trust models of the underlying
   applications.  In this sense, this section does not provide an
   overview of existing protocols as done in previous sections of the
   Internet Draft, but it rather explicitly describes what should be in
   place to ensure secure system operation.  Observe also that this list
   of security profiles is not exhaustive and that it should be
   considered just as an example not related to existing legal
   regulations for any existing application.  These security profiles
   are summarized in the table below:



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           +---------------------------------------------------------+
           | Exemnplary      |                                               |
           | Application     |          Description                  |
+----------+---------------------------------------------------------+
|SecProf_1 |Home usage       |Enables operation between home things  |
|          |                 |without interaction with central device|
+----------+-----------------+---------------------------------------+
|SecProf_2 |Managed Home     |Enables operation between home things. |
|          | usage           |Interaction with a central and local   |
|          |                 |device is possible                     |
+----------+-----------------+---------------------------------------+
|SecProf_3 |Industrial usage |Enables operation between things.      |
|          |                 |Relies on central (local or backend)   |
|          |                 |device for security                    |
+----------+-----------------+---------------------------------------+
|SecProf_4 |Advanced         |Enables ad-hoc operation between things|
|          |Industrial usage |and relies on central device or        |
|          |                 |on a collection of control devices     |
+----------+-----------------+---------------------------------------+

            Figure 5: Security profiles and application areas.

   The classification in the table considers different potential
   applications and situations in which their security needs change due
   to different operational features (network size, existence of a
   central device, connectivity to the Internet, importance of the
   exchanged information, etc) or threat model (what are the assets that
   an attacker looks for).  As already pointed out, this set of
   scenarios is exemplary and they should be further discussed based on
   a broader consensus.

   The security suite (SecProf_1) is catered for environments in which
   IP protocols (e.g., 6LoWPAN/CoAP) can be used to enable communication
   between things in an ad-hoc manner and the security requirements are
   minimal.  An example, is a home application in which two devices
   should exchange information and no further connection with other
   devices (local or with a backend) is required.  In this scenario,
   value of the exchanged information is low and that it usually happen
   in a confined room, thus, it is possible to have a short period of
   time during which initial secrets can be exchanged in the clear.  Due
   to this fact, there is no requirement to enable devices from
   different manufacturers to interoperate in a secure way (keys are
   just exchanged).  The expected network size of applications using
   this profile is expected to be small such that the provision of
   network security, e.g., secure routing, is of low importance.

   The next security suite (SecProf_2) represents an evolution of
   SecProf_1 in which, e.g., home devices, can be managed locally.  A



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   first possibility for the securing domain management refers to the
   creation of a centrally managed security domain without any
   connectivity to the Internet.  The central device used for management
   can serve as, e.g., a key distribution center including policies for
   key update, storage, etc.  The presence of a central device can help
   in the management of larger networks.  Network security becomes more
   relevant in this scenario since the IP network (e.g., 6LoWPAN/CoAP
   network) can be prone to Denial of Service attacks (e.g., flooding if
   L2 is not protected) or routing attacks.

   SecProf_3 considers that a central device is always required for
   network management.  Example applications of this profile include
   building control and automation, sensor networks for industrial use,
   environmental monitoring, etc.  As before, the network manager can be
   located in the IP network (e.g., 6LoWPAN/CoAP network) and handle key
   management.  In this case, the first association of devices to the
   network is required to be done in a secure way.  In other words, the
   threat model requires measurements to protect against any vulnerable
   period of time.  This step can involve the secure transmission of
   keying materials used for network security at different layers.  The
   information exchanged in the network is considered to be valuable and
   it should be protected in the sense of pairwise links.  Commands
   should be secured and broadcast should be secured with entity
   authentication [RFC7390].  Network should be protected from attacks.
   A further extension to this use case is to allow for remote
   management.  A "backend manager" is in charge of managing SW or
   information exchanged or collected within the IP network, e.g., a
   6LoWPAN/CoAP network.  This requires connection of devices to the
   Internet over a 6LBR involving a number of new threats that were not
   present before.  A list of potential attacks include: resource-
   exhaustion attacks from the Internet; amplification attacks; trust
   issues related a HTTP-CoAP proxy [ID-proHTTPCoAP], etc.  This use
   case requires protecting the communication from a device in the
   backend to a device in the IP network, e.g., a 6LoWPAN/CoAP network,
   end-to-end.  This use case also requires measures to provide the 6LBR
   with the capability of dropping fake requests coming from the
   Internet.  This becomes especially challenging when the 6LBR is not
   trusted and access to the exchanged information is limited; and even
   more in the case of a HTTP-CoAP proxy since protocol translation is
   required.  This use case should take care of protecting information
   accessed from the backend due to privacy issues (e.g., information
   such as type of devices, location, usage, type and amount of
   exchanged information, or mobility patterns can be gathered at the
   backend threatening the privacy sphere of users) so that only
   required information is disclosed.

   The last security suite (SecProf_4) essentially represents
   interoperability of all the security profiles defined previously.  It



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   considers applications with some additional requirements regarding
   operation such as: (i) ad-hoc establishment of security relationships
   between things (potentially from different manufacturers) in non-
   secure environments or (ii) dynamic roaming of things between
   different IP network security domains.  Such operational requirements
   pose additional security requirements, e.g., in addition to secure
   bootstrapping of a device within an IP, e.g., 6LowPan/CoAP, security
   domain and the secure transfer of network operational key, there is a
   need to enable inter-domains secure communication to facilitate data
   sharing.

   The above description illustrates how different applications of IP
   networks, e.g., 6LoWPAN/CoAP networks, involve different security
   needs.  In the following sections, we summarize the expected security
   features or capabilities for each the security profile with regards
   to "Security Architecture", "Security Model", "Security
   Bootstrapping", "Network Security", and "Application Security".

5.1.  Security Architecture

   Most things might be required to support both centralized and
   distributed operation patterns.  Distributed thing-to-thing
   communication might happen on demand, for instance, when two things
   form an ad-hoc security domain to cooperatively fulfill a certain
   task.  Likewise, nodes may communicate with a backend service located
   in the Internet without a central security manager.  The same nodes
   may also be part of a centralized architecture with a dedicated node
   being responsible for the security management for group communication
   between things in the IoT domain.  In today's IoT, most common
   architectures are fully centralized in the sense that all the
   security relationships within a segment are handled by a central
   party.  In the ZigBee standard, this entity is the trust center.
   Current proposals for 6LoWPAN/CoRE identify the 6LoWPAN Border Router
   (6LBR) as such a device.

   A centralized architecture allows for central management of devices
   and keying materials as well as for the backup of cryptographic keys.
   However, it also imposes some limitations.  First, it represents a
   single point of failure.  This is a major drawback, e.g., when key
   agreement between two devices requires online connectivity to the
   central node.  Second, it limits the possibility to create ad-hoc
   security domains without dedicated security infrastructure.  Third,
   it codifies a more static world view, where device roles are cast in
   stone, rather than a more dynamic world view that recognizes that
   networks and devices, and their roles and ownership, may change over
   time (e.g., due to device replacement and hand-over of control).





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   Decentralized architectures, on the other hand, allow creating ad-hoc
   security domains that might not require a single online management
   entity and are operative in a much more stand-alone manner.  The ad-
   hoc security domains can be added to a centralized architecture at a
   later point in time, allowing for central or remote management.

   The choice of security architecture has many implications regarding
   key management, access control, or security scope.  A distributed (or
   ad-hoc) architecture means that security relationships between things
   are setup on the fly between a number of objects and kept in a
   decentralized fashion.  A locally centralized security architecture
   means that a central device, e.g., the 6LBR, handles the keys for all
   the devices in the security domain.  Alternatively, a central
   security architecture could also refer to the fact that smart objects
   are managed from the backend.  The security architecture for the
   different security profiles is classified as follows.

             +---------------------------------------------------------+
             |                 Description                             |
  +----------+---------------------------------------------------------+
  |SecProf_1 |                Distributed                              |
  +----------+---------------------------------------------------------+
  |SecProf_2 |     Distributed able to move centralized (local)        |
  +----------+---------------------------------------------------------+
  |SecProf_3 |         Centralized (local &/or backend)                |
  +----------+---------------------------------------------------------+
  |SecProf_4 |      Distributed & centralized (local &/or backend)     |
  +----------+---------------------------------------------------------+

     Figure 6: Security architectures in different security profiles.

   In "SecProf_1", management mechanisms for the distributed assignment
   and management of keying materials is required.  Since this is a very
   simple use case, access control to the security domain can be enabled
   by means of a common secret known to all devices.  In the next
   security suite (SecProf_2), a central device can assume key
   management responsibilities and handle the access to the network.
   The last two security suites (SecProf_3 and SecProf_4) further allow
   for the management of devices or some keying materials from the
   backend.

5.2.  Security Model

   While some applications might involve very resource-constrained
   things such as, e.g., a humidity, pollution sensor, other
   applications might target more powerful devices aimed at more exposed
   applications.  Security parameters such as keying materials,
   certificates, etc must be protected in the thing, for example by



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   means of tamper-resistant hardware.  Keys may be shared across a
   thing's networking stack to provide authenticity and confidentiality
   in each networking layer.  This would minimize the number of key
   establishment/agreement handshake and incurs less overhead for
   constrained thing.  While more advance applications may require key
   separation at different networking layers, and possibly process
   separation and sandboxing to isolate one application from another.
   In this sense, this section reflects the fact that different
   applications require different sets of security mechanisms.

             +---------------------------------------------------------+
             |Description                                              |
  +----------+---------------------------------------------------------+
  |SecProf_1 |No tamper resistant                                      |
  |          |Sharing keys between layers                              |
  +----------+---------------------------------------------------------+
  |SecProf_2 |No tamper resistant                                      |
  |          |Sharing keys between layers                              |
  +----------+---------------------------------------------------------+
  |SecProf_3 |Tamper resistant                                         |
  |          |Key and process separation                               |
  +----------+---------------------------------------------------------+
  |SecProf_4 |(no) Tamper resistant                                    |
  |          |Sharing keys between layers/Key and process separation   |
  |          |Sandbox                                                  |
  +----------+---------------------------------------------------------+

      Figure 7: Thing security models in different security profiles.

5.3.  Security Bootstrapping and Management

   Bootstrapping refers to the process by which a thing initiates its
   life within a security domain and includes the initialization of
   secure and/or authentic parameters bound to the thing and at least
   one other device in the network.  Here, different mechanisms may be
   used to achieve confidentiality and/or authenticity of these
   parameters, depending on deployment scenario assumptions and the
   communication channel(s) used for passing these parameters.  The
   simplest mechanism for initial set-up of secure and authentic
   parameters is via communication in the clear using a physical
   interface (USB, wire, chip contact, etc.).  Here, one commonly
   assumes this communication channel is secure, since eavesdropping
   and/or manipulation of this interface would generally require access
   to the physical medium and, thereby, to one or both of the devices
   themselves.  This mechanism was used with the so-called original
   "resurrecting duckling" model, as introduced in [PROC-Stajano-99].
   This technique may also be used securely in wireless, rather than
   wired, set-ups, if the prospect of eavesdropping and/or manipulating



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   this channel are dim (a so-called "location-limited" channel
   [PROC-Smetters-04][PROC-Smetters-02]).  Examples hereof include the
   communication of secret keys in the clear using near field
   communication (NFC) - where the physical channel is purported to have
   very limited range (roughly 10cm), thereby thwarting eavesdropping by
   far-away adversarial devices, and in-the-clear communication during a
   small time window (triggered by, e.g., a button-push) - where
   eavesdropping is presumed absent during this small time window.  With
   the use of public-key based techniques, assumptions on the
   communication channel can be relaxed even further, since then the
   cryptographic technique itself provides for confidentiality of the
   channel set-up and the location-limited channel - or use of
   certificates - rules out man-in-the-middle attacks, thereby providing
   authenticity [PROC-Smetters-02].  The same result can be obtained
   using password-based public-key protocols [SPEKE], where authenticity
   depends on the (weak) password not being guessed during execution of
   the protocol.

   It should be noted that while most of these techniques realize a
   secure and authentic channel for passing parameters, these generally
   do not provide for explicit authorization.  As an example, with use
   of certificate-based public-key based techniques, one may obtain hard
   evidence on whom one shares secret and/or authentic parameters with,
   but this does not answer the question as to whether one wishes to
   share this information at all with this specifically identified
   device (the latter usually involves a human-decision element).  Thus,
   the bootstrapping mechanisms above should generally be complemented
   by mechanisms that regulate (security policies for) authorization.
   Furthermore, the type of bootstrapping is very related to the
   required type of security architecture.  Distributed bootstrapping
   means that a pair of devices can setup a security relationship on the
   fly, without interaction with a central device elsewhere within the
   system.  In many cases, it is handy to have a distributed
   bootstrapping protocol based on existing security protocols (e.g.,
   DTLS in CoAP) required for other purposes: this reduces the amount of
   required software.  A centralized bootstrapping protocol is one in
   which a central device manages the security relationships within a
   network.  This can happen locally, e.g., handled by the 6LBR, or
   remotely, e.g., from a server connected via the Internet.  The
   security bootstrapping for the different security profiles is as
   follows.










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             +---------------------------------------------------------+
             |Description                                              |
  +----------+---------------------------------------------------------+
  |SecProf_1 |* Distributed, (e.g., Resurrecting duckling)             |
  |          |* First key distribution happens in the clear            |
  +----------+---------------------------------------------------------+
  |SecProf_2 |* Distributed, (e.g., Resurrecting duckling )            |
  |          |* Centralized (local), 6LBR acts as KDC                  |
  |          |* First key distribution occurs in the clear, if the KDC |
  |          |  is available, the KDC can manage network access        |
  +----------+---------------------------------------------------------+
  |SecProf_3 |* 6LBR acts as KDC. It handles node joining, provides    |
  |          |  them with keying material from L2 to application layers|
  |          |* Bootstrapping occurs in a secure way - either in secure|
  |          |  environment or the security mechanisms ensure that     |
  |          |  eavesdropping is not possible.                         |
  |          |* KDC and backend can implement secure methods for       |
  |          |  network access                                         |
  +----------+---------------------------------------------------------+
  |SecProf_4 |* As in SecProf_3.                                       |
  +----------+---------------------------------------------------------+

      Figure 8: Security bootstrapping methods in different security
                                 profiles

5.4.  Network Security

   Network security refers to the mechanisms used to ensure the secure
   transport of 6LoWPAN frames.  This involves a multitude of issues
   ranging from secure discovery, frame authentication, routing
   security, detection of replay, secure group communication, etc.
   Network security is important to thwart potential attacks such as
   denial-of-service (e.g., through message flooding) or routing
   attacks.

   The Internet Draft [ID-Tsao] presents a very good overview of attacks
   and security needs classified according to the confidentiality,
   integrity, and availability needs.  A potential limitation is that
   there exist no differentiation in security between different use
   cases and the framework is limited to L3.  The security suites
   gathered in the present ID aim at solving this by allowing for a more
   flexible selection of security needs at L2 and L3.









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             +---------------------------------------------------------+
             |Description                                              |
  +----------+---------------------------------------------------------+
  |SecProf_1 |* Network key creating a home security domain at L2      |
  |          |  ensuring authentication and freshness of exchanged data|
  |          |* Secure multicast does not ensure origin authentication |
  |          |* No need for secure routing at L3                       |
  +----------+---------------------------------------------------------+
  |SecProf_2 |* Network key creating a home security domain at L2      |
  |          |  ensuring authentication and freshness of exchanged data|
  |          |* Secure multicast does not ensure origin authentication |
  |          |* No need for secure routing at L3                       |
  +----------+---------------------------------------------------------+
  |SecProf_3 |* Network key creating an industry security domain at L2 |
  |          |  ensuring authentication and freshness of exchanged data|
  |          |* Secure routing needed (integrity & availability) at L3 |
  |          |  within 6LoWPAN/CoAP                                    |
  |          |* Secure multicast requires origin authentication        |
  +----------+---------------------------------------------------------+
  |SecProf_4 |* Network key creating an industry security domain at L2 |
  |          |  ensuring authentication and freshness of exchanged data|
  |          |* Inter-domain authentication/secure handoff             |
  |          |* Secure routing needed at L3                            |
  |          |* Secure multicast requires origin authentication        |
  |          |* 6LBR (HTTP-CoAP proxy) requires verification of        |
  |          |  forwarded messages and messages leaving or entering the|
  |          |  6LoWPAN/CoAP network.                                  |
  +----------+---------------------------------------------------------+

      Figure 9: Network security needs in different security profiles

5.5.  Application Security

   In the context of 6LoWPAN/CoAP networks, application security refers
   firstly to the configuration of DTLS used to protect the exchanged
   information.  It further refers to the measures required in potential
   translation points (e.g., a (HTTP-CoAP) proxy) where information can
   be collected and the privacy sphere of users in a given security
   domain is endangered.  Application security for the different
   security profiles is as follows.











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             +---------------------------------------------------------+
             |Description                                              |
  +----------+---------------------------------------------------------+
  |SecProf_1 |  -                                                      |
  +----------+---------------------------------------------------------+
  |SecProf_2 |* DTLS is used for end-to-end application security       |
  |          |  between management device and things and between things|
  |          |* DTLS ciphersuites configurable to provide              |
  |          |  confidentiality and/or authentication and/or freshness |
  |          |* Key transport and policies for generation of session   |
  |          |  keys are required                                      |
  +----------+---------------------------------------------------------+
  |SecProf_3 |* Requirements as in SecProf_2 and                       |
  |          |* DTLS is used for end-to-end application security       |
  |          |  between management device and things and between things|
  |          |* Communication between KDC and each thing secured by    |
  |          |  pairwise keys                                          |
  |          |* Group keys for communication in a group distributed    |
  |          |  by KDC                                                 |
  |          |* Privacy protection should be provided in translation   |
  |          |  points                                                 |
  +----------+---------------------------------------------------------+
  |SecProf_4 |* Requirements as in SecProf_3 and                       |
  |          |* TLS or DTLS can be used to send commands from the      |
  |          |  backend to the 6LBR or things in a 6LoWPAN/CoAP network|
  |          |* End-to-end secure connectivity from backend required   |
  |          |* Secure broadcast in a network from backend required    |
  +----------+---------------------------------------------------------+

       Figure 10: Application security methods in different security
                                 profiles

   The first two security profiles do not include any security at the
   application layer.  The reason is that, in the first case, security
   is not provided and, in the second case, it seems reasonable to
   provide basic security at L2.  In the third security profile
   (SecProf_2), DTLS becomes the way of protecting messages at
   application layer between things and with the KDC running on a 6LBR.
   A key option refers to the capability of easily configuring DTLS to
   provide a subset of security services (e.g., some applications do not
   require confidentiality) to reduce the impact of security in the
   system operation of resource-constrained things.  In addition to
   basic key management mechanisms running within the KDC, communication
   protocols for key transport or key update are required.  These
   protocols could be based on DTLS.  The next security suite
   (SecProf_3) requires pairwise keys for communication between things
   within the security domain.  Furthermore, it can involve the usage of
   group keys for group communication.  If secure multicast is



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   implemented, it should provide origin authentication.  Finally,
   privacy protection should be taken into account to limit access to
   valuable information -- such as identifiers, type of collected data,
   traffic patterns -- in potential translation points (proxies) or in
   the backend.  The last security suite (SecProf_4) further extends the
   previous set of requirements considering security mechanisms to deal
   with translations between TLS and DTLS or for the provision of secure
   multicast within a 6LoWPAN/CoAP network from the backend.

6.  Challenges and Security Considerations for a Secure Internet of
    Things

   <<Oliver and Mohit add stuff in this section>>

   In this section, we take a closer look at the various security
   challenges in the operational and technical features of the IoT and
   then discuss how existing Internet security protocols cope with these
   technical and conceptual challenges through the lifecycle of a thing.
   Figure 2 summarizes which requirements need to be met in the
   lifecycle phases as well as some of the considered protocols.  This
   discussion should neither be understood as a comprehensive evaluation
   of all protocols, nor can it cover all possible aspects of IoT
   security.  Yet, it aims at showing concrete limitations of existing
   Internet security protocols in some areas rather than giving an
   abstract discussion about general properties of the protocols.  In
   this regard, the discussion handles issues that are most important
   from the authors' perspectives.

6.1.  Constraints and Heterogeneous Communication

   Coupling resource constrained networks and the powerful Internet is a
   challenge because the resulting heterogeneity of both networks
   complicates protocol design and system operation.  In the following
   we briefly discuss the resource constraints of IoT devices and the
   consequences for the use of Internet Protocols in the IoT domain.

6.1.1.  Tight Resource Constraints

   The IoT is a resource-constrained network that relies on lossy and
   low-bandwidth channels for communication between small nodes,
   regarding CPU, memory, and energy budget.  These characteristics
   directly impact the threats to and the design of security protocols
   for the IoT domain.  First, the use of small packets, e.g., IEEE
   802.15.4 supports 127-byte sized packets at the physical layer, may
   result in fragmentation of larger packets of security protocols.
   This may open new attack vectors for state exhaustion DoS attacks,
   which is especially tragic, e.g., if the fragmentation is caused by
   large key exchange messages of security protocols.  Moreover, packet



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   fragmentation commonly downgrades the overall system performance due
   to fragment losses and the need for retransmissions.  For instance,
   fate-sharing packet flight as implemented by DTLS might aggravate the
   resulting performance loss.

   The size and number of messages should be minimized to reduce memory
   requirements and optimize bandwidth usage.  In this context, layered
   approaches involving a number of protocols might lead to worse
   performance in resource-constrained devices since they combine the
   headers of the different protocols.  In some settings, protocol
   negotiation can increase the number of exchanged messages.  To
   improve performance during basic procedures such as, e.g.,
   bootstrapping, it might be a good strategy to perform those
   procedures at a lower layer.

   Small CPUs and scarce memory limit the usage of resource-expensive
   cryptoprimitives such as public-key cryptography as used in most
   Internet security standards.  This is especially true, if the basic
   cryptoblocks need to be frequently used or the underlying application
   demands a low delay.

   Independently from the development in the IoT domain, all discussed
   security protocols show efforts to reduce the cryptographic cost of
   the required public-key-based key exchanges and signatures with
   ECC[RFC5246][RFC5903][RFC7401][ID-HIP].  Moreover, all protocols have
   been revised in the last years to enable crypto agility, making
   cryptographic primitives interchangeable.  However, these
   improvements are only a first step in reducing the computation and
   communication overhead of Internet protocols.  The question remains
   if other approaches can be applied to leverage key agreement in these
   heavily resource-constrained environments.

   A further fundamental need refers to the limited energy budget
   available to IoT nodes.  Careful protocol (re)design and usage is
   required to reduce not only the energy consumption during normal
   operation, but also under DoS attacks.  Since the energy consumption
   of IoT devices differs from other device classes, judgments on the
   energy consumption of a particular protocol cannot be made without
   tailor-made IoT implementations.

6.1.2.  Denial-of-Service Resistance

   The tight memory and processing constraints of things naturally
   alleviate resource exhaustion attacks.  Especially in unattended T2T
   communication, such attacks are difficult to notice before the
   service becomes unavailable (e.g., because of battery or memory
   exhaustion).  As a DoS countermeasure, DTLS, IKEv2, HIP, and Diet HIP
   implement return routability checks based on a cookie mechanism to



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   delay the establishment of state at the responding host until the
   address of the initiating host is verified.  The effectiveness of
   these defenses strongly depends on the routing topology of the
   network.  Return routability checks are particularly effective if
   hosts cannot receive packets addressed to other hosts and if IP
   addresses present meaningful information as is the case in today's
   Internet.  However, they are less effective in broadcast media or
   when attackers can influence the routing and addressing of hosts
   (e.g., if hosts contribute to the routing infrastructure in ad-hoc
   networks and meshes).

   In addition, HIP implements a puzzle mechanism that can force the
   initiator of a connection (and potential attacker) to solve
   cryptographic puzzles with variable difficulties.  Puzzle-based
   defense mechanisms are less dependent on the network topology but
   perform poorly if CPU resources in the network are heterogeneous
   (e.g., if a powerful Internet host attacks a thing).  Increasing the
   puzzle difficulty under attack conditions can easily lead to
   situations, where a powerful attacker can still solve the puzzle
   while weak IoT clients cannot and are excluded from communicating
   with the victim.  Still, puzzle-based approaches are a viable option
   for sheltering IoT devices against unintended overload caused by
   misconfigured or malfunctioning things.

6.1.3.  Protocol Translation and End-to-End Security

   Even though 6LoWPAN and CoAP progress towards reducing the gap
   between Internet protocols and the IoT, they do not target protocol
   specifications that are identical to their Internet counterparts due
   to performance reasons.  Hence, more or less subtle differences
   between IoT protocols and Internet protocols will remain.  While
   these differences can easily be bridged with protocol translators at
   gateways, they become major obstacles if end-to-end security measures
   between IoT devices and Internet hosts are used.

   Cryptographic payload processing applies message authentication codes
   or encryption to packets.  These protection methods render the
   protected parts of the packets immutable as rewriting is either not
   possible because a) the relevant information is encrypted and
   inaccessible to the gateway or b) rewriting integrity-protected parts
   of the packet would invalidate the end-to-end integrity protection.

   There are essentially four solutions for this problem:

   1.  Sharing credentials with gateways enables gateways to transform
       (e.g., de-compress, convert, etc.) packets and re-apply the
       security measures after transformation.  This method abandons




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       end-to-end security and is only applicable to simple scenarios
       with a rudimentary security model.

   2.  Reusing the Internet wire format in the IoT makes conversion
       between IoT and Internet protocols unnecessary.  However, it
       leads to poor performance because IoT specific optimizations
       (e.g., stateful or stateless compression) are not possible.

   3.  Selectively protecting vital and immutable packet parts with a
       MAC or with encryption requires a careful balance between
       performance and security.  Otherwise, this approach will either
       result in poor performance (protect as much as possible) or poor
       security (compress and transform as much as possible).

   4.  Message authentication codes that sustain transformation can be
       realized by considering the order of transformation and
       protection (e.g., by creating a signature before compression so
       that the gateway can decompress the packet without recalculating
       the signature).  This enables IoT specific optimizations but is
       more complex and may require application-specific transformations
       before security is applied.  Moreover, it cannot be used with
       encrypted data because the lack of cleartext prevents gateways
       from transforming packets.

   5.  Object security based mechanisms can bridge the protocol worlds,
       but still requires that the two worlds use the same object
       security formats.  Currently the IoT based object security format
       based on COSE is different from the Internet based JOSE or CMS.
       Legacy devices on the Internet side will need to update to the
       newer IoT protocols to enable real end-to-end security.

   To the best of our knowledge, none of the mentioned security
   protocols provides a fully customizable solution in this problem
   space.

6.2.  Bootstrapping of a Security Domain

   Creating a security domain from a set of previously unassociated IoT
   devices is a key operation in the lifecycle of a thing and in the IoT
   network.  This aspect is further elaborated and discussed in the
   T2TRG draft on bootstrapping [ID-bootstrap].

6.3.  Operation

   After the bootstrapping phase, the system enters the operational
   phase.  During the operational phase, things can relate to the state
   information created during the bootstrapping phase in order to
   exchange information securely and in an authenticated fashion.  In



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   this section, we discuss aspects of communication patterns and
   network dynamics during this phase.

6.3.1.  End-to-End Security

   Providing end-to-end security is of great importance to address and
   secure individual T2T or H2T communication within one IoT domain.
   Moreover, end-to-end security associations are an important measure
   to bridge the gap between the IoT and the Internet.  IKEv2 and HIP,
   TLS and DTLS provide end-to-end security services including peer
   entity authentication, end-to-end encryption and integrity protection
   above the network layer and the transport layer respectively.  Once
   bootstrapped, these functions can be carried out without online
   connections to third parties, making the protocols applicable for
   decentralized use in the IoT.  However, protocol translation by
   intermediary nodes may invalidate end-to-end protection measures (see
   Section 5.1).  Also these protocols require end-to-end connectivity
   between the devices and do not support store-and-forward scenarios.
   Object security is an option for such scenarios and the work on
   OSCOAP [ID-OSCOAP] is a potential solution in this space, in
   particular, in the context of forwarding proxies.

6.3.2.  Group Membership and Security

   In addition to end-to-end security, group key negotiation is an
   important security service for the T2Ts and Ts2T communication
   patterns in the IoT as efficient local broadcast and multicast relies
   on symmetric group keys.

   All discussed protocols only cover unicast communication and
   therefore do not focus on group-key establishment.  However, the
   Diffie-Hellman keys that are used in IKEv2 and HIP could be used for
   group Diffie-Hellman key-negotiations.  Conceptually, solutions that
   provide secure group communication at the network layer (IPsec/IKEv2,
   HIP/Diet HIP) may have an advantage regarding the cryptographic
   overhead compared to application-focused security solutions (TLS/
   DTLS or OSCOAP).  This is due to the fact that application-focused
   solutions require cryptographic operations per group application,
   whereas network layer approaches may allow to share secure group
   associations between multiple applications (e.g., for neighbor
   discovery and routing or service discovery).  Hence, implementing
   shared features lower in the communication stack can avoid redundant
   security measures.

   A number of group key solutions have been developed in the context of
   the IETF working group MSEC in the context of the MIKEY architecture
   [WG-MSEC][RFC4738].  These are specifically tailored for multicast
   and group broadcast applications in the Internet and should also be



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   considered as candidate solutions for group key agreement in the IoT.
   The MIKEY architecture describes a coordinator entity that
   disseminates symmetric keys over pair-wise end-to-end secured
   channels.  However, such a centralized approach may not be applicable
   in a distributed environment, where the choice of one or several
   coordinators and the management of the group key is not trivial.

6.3.3.  Mobility and IP Network Dynamics

   It is expected that many things (e.g., wearable sensors, and user
   devices) will be mobile in the sense that they are attached to
   different networks during the lifetime of a security association.
   Built-in mobility signaling can greatly reduce the overhead of the
   cryptographic protocols because unnecessary and costly re-
   establishments of the session (possibly including handshake and key
   agreement) can be avoided.  IKEv2 supports host mobility with the
   MOBIKE [RFC4555][RFC4621] extension.  MOBIKE refrains from applying
   heavyweight cryptographic extensions for mobility.  However, MOBIKE
   mandates the use of IPsec tunnel mode which requires to transmit an
   additional IP header in each packet.  This additional overhead could
   be alleviated by using header compression methods or the Bound End-
   to-End Tunnel (BEET) mode [ID-Nikander], a hybrid of tunnel and
   transport mode with smaller packet headers.

   HIP offers a simple yet effective mobility management by allowing
   hosts to signal changes to their associations [RFC5206].  However,
   slight adjustments might be necessary to reduce the cryptographic
   costs, for example, by making the public-key signatures in the
   mobility messages optional.  Diet HIP does not define mobility yet
   but it is sufficiently similar to HIP to employ the same mechanisms.
   TLS and DTLS do not have standards for mobility support, however,
   work on DTLS mobility exists in the form of an Internet draft
   [ID-Williams].  The specific need for IP-layer mobility mainly
   depends on the scenario in which nodes operate.  In many cases,
   mobility support by means of a mobile gateway may suffice to enable
   mobile IoT networks, such as body sensor networks.  However, if
   individual things change their point of network attachment while
   communicating, mobility support may gain importance.

6.4.  Software update

   IoT devices have a reputation for being insecure at the time of
   manufacture.  Yet they are often expected to stay functional in live
   deployments for years and even decades.  Additionally, these devices
   typically operate unattended with direct Internet connectivity.
   Therefore, a remote software update mechanism to fix vulnerabilities,
   to update configuration settings, and for adding new functionality is
   needed.



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   Schneier [SchneierSecurity] in his essay expresses concerns about the
   status of software and firmware update mechanisms for Internet of
   Things (IoT) devices.  He highlights several challenges that hinder
   mechanisms for secure software update of IoT devices.  First, there
   is a lack of incentives for manufactures, vendors and others on the
   supply chain to issue updates for their devices.  Second, parts of
   the software running on the IoT devices is simply a binary blob
   without any source code available.  Since the complete source code
   isn't available, no patches can be written for that piece of code.
   Third, even when updates are available, users generally have to
   manually download and install those updates.  However, users are
   never alerted about security updates and many times don't have the
   necessary expertise to manually administer the required updates.

   The FTC staff report on Internet of Things - Privacy & Security in a
   Connected World [FTCreport] and the Article 29 Working Party Opinion
   8/2014 on the on Recent Developments on the Internet of Things
   [Article29] also document the challenges for secure remote software
   update of IoT devices.  They note that even providing such a software
   update capability may add new vulnerabilities for constrained
   devices.  For example, a buffer overflow vulnerability in the
   implementation of a software update protocol (TR69) [TR69] and an
   expired certificate in a hub device [wink] demonstrate how the
   software update process itself can introduce vulnerabilities.

   While powerful IoT devices that run general purpose operating systems
   can make use of sophisticated software update mechanisms known from
   the desktop world, a more considerate effort is needed for resource-
   constrained devices that don't have any operating system and are
   typically not equipped with a memory management unit or similar
   tools.  The IAB also organized a workshop to understand the
   challenges for secure software update of IoT devices.  A summary of
   the workshop and the proposed next steps have been documented
   [iotsu].

6.5.  Verifying device behavior

   Users often have a false sense of privacy when using new Internet of
   Things (IoT) appliances such as Internet-connected smart televisions,
   speakers and cameras.  Recent revelations have shown that this user
   belief is often unfounded.  Many IoT device vendors have been caught
   collecting sensitive private data through these connected appliances
   with or without appropriate user warnings [cctv].

   An IoT device user/owner would like to monitor and know if the device
   is calling home (i.e. verify its operational behavior).  The calling
   home feature may be necessary in some scenarios, such as during the
   initial configuration of the device.  However, the user should be



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   kept aware of the data that the device is sending back to the vendor.
   For example, the user should be ensured that his/her TV is not
   sending data when he/she inserts a new USB stick.

   Providing such information to the users in an understandable fashion
   is challenging.  This is because the IoT device are not only
   resource-constrained in terms of their computational capability, but
   also in terms of the user interface available.  Also, the network
   infrastructure where these devices are deployed will vary
   significantly from one user environment to another.  Therefore, where
   and how this monitoring feature is implemented still remains an open
   question.

6.6.  End-of-life

   Like all commercial devices, most IoT devices will be end-of-lifed by
   vendors.  This may be planned or unplanned (for example when the
   vendor or manufacturer goes bankrupt).  A user should still be able
   to use and perhaps even update the device.  This requires for some
   form of authorization handover.

   Although this may seem far fetched given the commercial interests and
   market dynamics, we have examples from the mobile world where the
   devices have been functional and up-to-date long after the original
   vendor stopped supporting the device.  CyanogenMod for Android
   devices and OpenWrt for home routers are two such instances where
   users have been able to use and update their devices even after they
   were end-of-lifed.  Admittedly these are not easy for an average
   users to install and configure on their devices.  With the deployment
   of millions of IoT devices, simpler mechanisms are needed to allow
   users to add new root-of-trusts and install software and firmware
   from other sources once the device has been end-of-lifed.

6.7.  Penetration testing

   Given that the IoT devices often have inadvertent vulnerabilities,
   both users and developers would want to perform penetration testing
   on their IoT devices.  Nonetheless, since the devices are resource-
   constrained they often barf of crash even when minimal tests are
   performed.  It remains to be seen how the software testing and
   quality assurance mechanisms used from the desktop and mobile world
   will be applied to IoT devices.

6.8.  Quantum-resistance

   Many IoT systems that are being deployed today will remain
   operational for many years.  With the advancements made in the field
   of quantum computers, it is possible that large-scale quantum



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   computers are available in the future for performing cryptanalysis on
   existing cryptographic algorithms and cipher suites.  If this
   happened, it would have two consequences.  First, functionalities
   enabled by means of RSA/ECC - namely key exchange, public-key
   encryption and signature - would not be secure anymore due to Shor's
   algorithm.  Second, the security level of symmetric algorithms will
   decrease, e.g., the security of a block cipher with a key size of b
   bits will only offer b/2 bits of security due to Grover's algorithm.

   This would require to update to quantum-resistant alternatives, in
   particular, for those functionalities involving key exchange, public-
   key encryption and signatures.  While such future planning is hard,
   it may be a necessity in certain critical IoT deployments which are
   expected to last decades or more.  Although increasing the key-size
   of the different algorithms is definitely an option, it would also
   incur additional computation overhead and network traffic.  This
   would be undesirable in most scenarios.  There have been recent
   advancements in quantum-resistant cryptography.

   We refer to [ETSI_GR_QSC_001] for an extensive overview of existing
   quantum-resistant cryptography.  RFC7696 provides guidelines for
   cryptographic algorithm agility.

7.  Next Steps towards a Flexible and Secure Internet of Things

   This Internet Draft included an overview of both operational and
   security requirements of things in the Internet of Things, discussed
   a general threat model and security issues, and introduced a number
   of potential security suites fitting different types of IoT
   deployments.

   We conclude this document by giving our assessment of the current
   status of IoT security with respect to addressing the IP security
   challenges.  <<TBD>>

8.  Security Considerations

   This document reflects upon the requirements and challenges of the
   security architectural framework for Internet of Things.

9.  IANA Considerations

   This document contains no request to IANA.








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10.  Acknowledgements

   We gratefully acknowledge feedback and fruitful discussion with
   Tobias Heer and Robert Moskowitz.  Acknowledge the additional authors
   of the previous version of this document Sye Loong Keoh, Rene Hummen
   and Rene Struik.

11.  Informative References

   [Article29]
              "Opinion 8/2014 on the on Recent Developments on the
              Internet of Things", Web http://ec.europa.eu/justice/data-
              protection/article-29/documentation/opinion-
              recommendation/files/2014/wp223_en.pdf, n.d..

   [AUTO-ID]  "AUTO-ID LABS", Web http://www.autoidlabs.org/, September
              2010.

   [BACNET]   "BACnet", Web http://www.bacnet.org/, February 2011.

   [cctv]     "Backdoor In MVPower DVR Firmware Sends CCTV Stills To an
              Email Address In China", Web
              https://hardware.slashdot.org/story/16/02/17/0422259/
              backdoor-in-mvpower-dvr-firmware-sends-cctv-stills-to-an-
              email-address-in-china, n.d..

   [DALI]     "DALI", Web http://www.dalibydesign.us/dali.html, February
              2011.

   [ETSI_GR_QSC_001]
              "Quantum-Safe Cryptography (QSC);Quantum-safe algorithmic
              framework", European Telecommunications Standards
              Institute (ETSI) , June 2016.

   [FTCreport]
              "FTC Report on Internet of Things Urges Companies to Adopt
              Best Practices to Address Consumer Privacy and Security
              Risks", Web https://www.ftc.gov/news-events/press-
              releases/2015/01/ftc-report-internet-things-urges-
              companies-adopt-best-practices, n.d..

   [ID-bootstrap]
              Sarikaya, B. and M. Sethi, "Secure IoT Bootstrapping : A
              Survey", draft-sarikaya-t2trg-sbootstrapping-01 , July
              2016.






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   [ID-Daniel]
              Park, S., Kim, K., Haddad, W., Chakrabarti, S., and J.
              Laganier, "IPv6 over Low Power WPAN Security Analysis",
              Internet Draft draft-daniel-6lowpan-security-analysis-05,
              March 2011.

   [ID-Hartke]
              Hartke, K. and O. Bergmann, "Datagram Transport Layer
              Security in Constrained Environments", draft-hartke-core-
              codtls-02 (work in progress), July 2012.

   [ID-HIP]   Moskowitz, R., "HIP Diet EXchange (DEX)", draft-moskowitz-
              hip-rg-dex-06 (work in progress), May 2012.

   [ID-Nikander]
              Nikander, P. and J. Melen, "A Bound End-to-End
              Tunnel(BEET) mode for ESP", draft-nikander-esp-beet-
              mode-09 , August 2008.

   [ID-OFlynn]
              O'Flynn, C., Sarikaya, B., Ohba, Y., Cao, Z., and R.
              Cragie, "Security Bootstrapping of Resource-Constrained
              Devices", draft-oflynn-core-bootstrapping-03 (work in
              progress), November 2010.

   [ID-OSCOAP]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security of CoAP (OSCOAP)", draft-selander-ace-
              object-security-05 , July 2016.

   [ID-proHTTPCoAP]
              Castellani, A., Loreto, S., Rahman, A., Fossati, T., and
              E. Dijk, "Best practices for HTTP-CoAP mapping
              implementation", draft-castellani-core-http-mapping-
              07(work in progress), February 2013.

   [ID-Tsao]  Tsao, T., Alexander, R., Dohler, M., Daza, V., and A.
              Lozano, "A Security Framework for Routing over Low Power
              and Lossy Networks", draft-ietf-roll-security-
              framework-07 , January 2012.

   [ID-Williams]
              Williams, M. and J. Barrett, "Mobile DTLS", draft-barrett-
              mobile-dtls-00 , March 2009.







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   [iotsu]    "Patching the Internet of Things: IoT Software Update
              Workshop 2016", Web
              https://www.ietf.org/blog/2016/07/patching-the-internet-
              of-things-iot-software-update-workshop-2016/, n.d..

   [JOURNAL-Perrig]
              Perrig, A., Szewczyk, R., Wen, V., Culler, D., and J.
              Tygar, "SPINS: Security protocols for Sensor Networks",
              Journal Wireless Networks, September 2002.

   [NIST]     Dworkin, M., "NIST Specification Publication 800-38B",
              2005.

   [PROC-Chan]
              Chan, H., Perrig, A., and D. Song, "Random Key
              Predistribution Schemes for Sensor Networks",
              Proceedings IEEE Symposium on Security and Privacy, 2003.

   [PROC-Gupta]
              Gupta, V., Wurm, M., Zhu, Y., Millard, M., Fung, S., Gura,
              N., Eberle, H., and S. Shantz, "Sizzle: A Standards-based
              End-to-End Security Architecture for the Embedded
              Internet", Proceedings Pervasive Computing and
              Communications (PerCom), 2005.

   [PROC-Smetters-02]
              Balfanz, D., Smetters, D., Steward, P., and H. Chi Wong,,
              "Talking To Strangers: Authentication in Ad-Hoc Wireless
              Networks", Paper NDSS, 2002.

   [PROC-Smetters-04]
              Balfanz, D., Durfee, G., Grinter, R., Smetters, D., and P.
              Steward, "Network-in-a-Box: How to Set Up a Secure
              Wireless Network in Under a Minute", Paper USENIX, 2004.

   [PROC-Stajano-99]
              Stajano, F. and R. Anderson, "Resurrecting Duckling -
              Security Issues for Adhoc Wireless Networks",
              7th International Workshop Proceedings, November 1999.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <http://www.rfc-editor.org/info/rfc2818>.



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   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
              <http://www.rfc-editor.org/info/rfc3748>.

   [RFC3756]  Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
              Neighbor Discovery (ND) Trust Models and Threats",
              RFC 3756, DOI 10.17487/RFC3756, May 2004,
              <http://www.rfc-editor.org/info/rfc3756>.

   [RFC3833]  Atkins, D. and R. Austein, "Threat Analysis of the Domain
              Name System (DNS)", RFC 3833, DOI 10.17487/RFC3833, August
              2004, <http://www.rfc-editor.org/info/rfc3833>.

   [RFC4016]  Parthasarathy, M., "Protocol for Carrying Authentication
              and Network Access (PANA) Threat Analysis and Security
              Requirements", RFC 4016, DOI 10.17487/RFC4016, March 2005,
              <http://www.rfc-editor.org/info/rfc4016>.

   [RFC4251]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Protocol Architecture", RFC 4251, DOI 10.17487/RFC4251,
              January 2006, <http://www.rfc-editor.org/info/rfc4251>.

   [RFC4555]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol
              (MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,
              <http://www.rfc-editor.org/info/rfc4555>.

   [RFC4621]  Kivinen, T. and H. Tschofenig, "Design of the IKEv2
              Mobility and Multihoming (MOBIKE) Protocol", RFC 4621,
              DOI 10.17487/RFC4621, August 2006,
              <http://www.rfc-editor.org/info/rfc4621>.

   [RFC4738]  Ignjatic, D., Dondeti, L., Audet, F., and P. Lin, "MIKEY-
              RSA-R: An Additional Mode of Key Distribution in
              Multimedia Internet KEYing (MIKEY)", RFC 4738,
              DOI 10.17487/RFC4738, November 2006,
              <http://www.rfc-editor.org/info/rfc4738>.








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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, DOI 10.17487/RFC4919, August 2007,
              <http://www.rfc-editor.org/info/rfc4919>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <http://www.rfc-editor.org/info/rfc4944>.

   [RFC5191]  Forsberg, D., Ohba, Y., Ed., Patil, B., Tschofenig, H.,
              and A. Yegin, "Protocol for Carrying Authentication for
              Network Access (PANA)", RFC 5191, DOI 10.17487/RFC5191,
              May 2008, <http://www.rfc-editor.org/info/rfc5191>.

   [RFC5206]  Nikander, P., Henderson, T., Ed., Vogt, C., and J. Arkko,
              "End-Host Mobility and Multihoming with the Host Identity
              Protocol", RFC 5206, DOI 10.17487/RFC5206, April 2008,
              <http://www.rfc-editor.org/info/rfc5206>.

   [RFC5238]  Phelan, T., "Datagram Transport Layer Security (DTLS) over
              the Datagram Congestion Control Protocol (DCCP)",
              RFC 5238, DOI 10.17487/RFC5238, May 2008,
              <http://www.rfc-editor.org/info/rfc5238>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5713]  Moustafa, H., Tschofenig, H., and S. De Cnodder, "Security
              Threats and Security Requirements for the Access Node
              Control Protocol (ANCP)", RFC 5713, DOI 10.17487/RFC5713,
              January 2010, <http://www.rfc-editor.org/info/rfc5713>.

   [RFC5903]  Fu, D. and J. Solinas, "Elliptic Curve Groups modulo a
              Prime (ECP Groups) for IKE and IKEv2", RFC 5903,
              DOI 10.17487/RFC5903, June 2010,
              <http://www.rfc-editor.org/info/rfc5903>.

   [RFC6345]  Duffy, P., Chakrabarti, S., Cragie, R., Ohba, Y., Ed., and
              A. Yegin, "Protocol for Carrying Authentication for
              Network Access (PANA) Relay Element", RFC 6345,
              DOI 10.17487/RFC6345, August 2011,
              <http://www.rfc-editor.org/info/rfc6345>.





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   [RFC6568]  Kim, E., Kaspar, D., and JP. Vasseur, "Design and
              Application Spaces for IPv6 over Low-Power Wireless
              Personal Area Networks (6LoWPANs)", RFC 6568,
              DOI 10.17487/RFC6568, April 2012,
              <http://www.rfc-editor.org/info/rfc6568>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <http://www.rfc-editor.org/info/rfc7252>.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <http://www.rfc-editor.org/info/rfc7296>.

   [RFC7390]  Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
              the Constrained Application Protocol (CoAP)", RFC 7390,
              DOI 10.17487/RFC7390, October 2014,
              <http://www.rfc-editor.org/info/rfc7390>.

   [RFC7401]  Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
              Henderson, "Host Identity Protocol Version 2 (HIPv2)",
              RFC 7401, DOI 10.17487/RFC7401, April 2015,
              <http://www.rfc-editor.org/info/rfc7401>.

   [RFC7696]  Housley, R., "Guidelines for Cryptographic Algorithm
              Agility and Selecting Mandatory-to-Implement Algorithms",
              BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
              <http://www.rfc-editor.org/info/rfc7696>.

   [SchneierSecurity]
              "The Internet of Things Is Wildly Insecure--And Often
              Unpatchable", Web
              https://www.schneier.com/essays/archives/2014/01/
              the_internet_of_thin.html, n.d..

   [THESIS-Langheinrich]
              Langheinrich, M., "Personal Privacy in Ubiquitous
              Computing", PhD Thesis ETH Zurich, 2005.

   [Thread]   "Thread Alliance", Web http://threadgroup.org/, n.d..

   [TinyDTLS]
              "TinyDTLS", Web http://tinydtls.sourceforge.net/, February
              2012.





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   [TR69]     "Too Many Cooks - Exploiting the Internet-of-TR-
              069-Things", Web https://media.ccc.de/v/31c3_-_6166_-_en_-
              _saal_6_-_201412282145_-_too_many_cooks_-
              _exploiting_the_internet-of-tr-069-things_-
              _lior_oppenheim_-_shahar_tal, n.d..

   [WG-6LoWPAN]
              "IETF 6LoWPAN Working Group",
              Web http://tools.ietf.org/wg/6lowpan/, February 2011.

   [WG-CoRE]  "IETF Constrained RESTful Environment (CoRE) Working
              Group", Web https://datatracker.ietf.org/wg/core/charter/,
              February 2011.

   [WG-MSEC]  "MSEC Working Group",
              Web http://datatracker.ietf.org/wg/msec/, n.d..

   [wink]     "Wink's Outage Shows Us How Frustrating Smart Homes Could
              Be",
              Web http://www.wired.com/2015/04/smart-home-headaches/,
              n.d..

   [ZB]       "ZigBee Alliance", Web http://www.zigbee.org/, February
              2011.

Authors' Addresses

   Oscar Garcia-Morchon
   Philips Research
   Canal Park 2
   Cambridge,   02141
   United States

   Email: oscar.garcia@philips.com


   Sandeep S. Kumar
   Philips Research
   High Tech Campus
   Eindhoven,   5656 AE
   The Netherlands

   Email: sandeep.kumar@philips.com








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   Mohit Sethi
   Ericsson
   Hirsalantie 11
   Jorvas
   Finland

   Email: mohit@piuha.net










































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