Network Working Group                                  O. Garcia-Morchon
Internet-Draft                                              Philips IP&S
Intended status: Informational                                  S. Kumar
Expires: March 23, 2018                                 Philips Research
                                                                M. Sethi
                                                      September 19, 2017

  State-of-the-Art and Challenges for the Internet of Things Security


   The Internet of Things (IoT) concept refers to the usage of standard
   Internet protocols to allow for human-to-thing and thing-to-thing
   communication.  The security needs for the IoT are well-recognized
   and many standardization steps for providing security have been
   taken, for example, the specification of Constrained Application
   Protocol (CoAP) over Datagram Transport Layer Security (DTLS).
   However, security challenges still exist and there are some use cases
   that lack a suitable solution.  In this document, we first discuss
   the various stages in the lifecycle of a thing.  Next, we document
   the various security threats to a thing and the challenges that one
   might face to protect against these threats.  Lastly, we discuss the
   next steps needed to facilitate the deployment of secure IoT systems.

   This document is a product of the IRTF Thing-to-Thing Research Group

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
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   This Internet-Draft will expire on March 23, 2018.

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Copyright Notice

   Copyright (c) 2017 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Motivation and background . . . . . . . . . . . . . . . . . .   4
     2.1.  The Thing Lifecycle . . . . . . . . . . . . . . . . . . .   4
     2.2.  Security building blocks  . . . . . . . . . . . . . . . .   5
   3.  Security Threats and Managing Risk  . . . . . . . . . . . . .   9
   4.  State-of-the-Art  . . . . . . . . . . . . . . . . . . . . . .  13
     4.1.  IP-based IoT Protocols and Standards  . . . . . . . . . .  13
     4.2.  Existing IP-based Security Protocols and Solutions  . . .  16
     4.3.  IoT Security Guidelines . . . . . . . . . . . . . . . . .  19
   5.  Challenges for a Secure IoT . . . . . . . . . . . . . . . . .  22
     5.1.  Constraints and Heterogeneous Communication . . . . . . .  22
       5.1.1.  Resource Constraints  . . . . . . . . . . . . . . . .  23
       5.1.2.  Denial-of-Service Resistance  . . . . . . . . . . . .  24
       5.1.3.  End-to-end security, protocol translation, and the
               role of middleboxes . . . . . . . . . . . . . . . . .  24
       5.1.4.  New network architectures and paradigm  . . . . . . .  26
     5.2.  Bootstrapping of a Security Domain  . . . . . . . . . . .  27
     5.3.  Operational Challenges  . . . . . . . . . . . . . . . . .  27
       5.3.1.  Group Membership and Security . . . . . . . . . . . .  27
       5.3.2.  Mobility and IP Network Dynamics  . . . . . . . . . .  28
     5.4.  Software update . . . . . . . . . . . . . . . . . . . . .  29
     5.5.  Verifying device behavior . . . . . . . . . . . . . . . .  30
     5.6.  End-of-Life . . . . . . . . . . . . . . . . . . . . . . .  31
     5.7.  Testing: bug hunting and vulnerabilities  . . . . . . . .  31
     5.8.  Quantum-resistance  . . . . . . . . . . . . . . . . . . .  31
     5.9.  Privacy protection  . . . . . . . . . . . . . . . . . . .  32
     5.10. Data leakage  . . . . . . . . . . . . . . . . . . . . . .  33
     5.11. Trustworthy IoT Operation . . . . . . . . . . . . . . . .  34
   6.  Conclusions and Next Steps  . . . . . . . . . . . . . . . . .  34
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  35
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  35

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   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  35
   10. Informative References  . . . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  46

1.  Introduction

   The Internet of Things (IoT) denotes the interconnection of highly
   heterogeneous networked entities and networks that follow a number of
   different 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 which had envisioned a world where every physical
   object is tagged with a radio-frequency identification (RFID) tag
   having a globally unique identifier.  This would not only allow
   tracking of objects in real-time but also allow querying of data
   about them over the Internet.  However, since then, the meaning of
   the Internet of Things has expanded and now encompasses a wide
   variety of technologies, objects and protocols.  It is not surprising
   that the IoT has received significant attention from the research
   community to (re)design, apply, and use standard Internet technology
   and protocols for the IoT.

   The things that are part of the Internet of Things are no longer
   unresponsive and have transformed into computing devices that
   understand and react to the environment they reside in.  These things
   are also often referred to as smart objects or smart devices.

   The introduction of IPv6 [RFC6568] and CoAP [RFC7252] as fundamental
   building blocks for IoT applications allows connecting IoT hosts to
   the Internet.  This brings several advantages including: (i) a
   homogeneous protocol ecosystem that allows simple integration with
   other Internet hosts; (ii) simplified development for devices that
   significantly vary in their capabilities; (iii) a unified interface
   for applications, removing the need for application-level proxies.
   These building blocks greatly simplify the deployment of the
   envisioned scenarios which range from building automation to
   production environments and personal area networks.

   This document presents an overview of important security aspects for
   the Internet of Things.  We begin by discussing the lifecycle of a
   thing and giving general definitions of the security building blocks
   in Section 2.  In Section 3, we discuss security threats for the IoT
   and methodologies for managing these threats when designing a secure
   system.  Section 4 reviews existing IP-based (security) protocols for
   the IoT and briefly summarizes existing guidelines and regulations.
   Section 5 identifies remaining challenges for a secure IoT and
   discusses potential solutions.  Section 6 includes final remarks and

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   The first draft version of this document was submitted in March 2011.
   Initial draft versions of this document were presented and discussed
   during the CORE meetings at IETF 80 and later.  Discussions on
   security lifecycle at IETF 92 (March 2015) evolved into more general
   security considerations.  Thus, the draft was selected to address the
   T2TRG work item on the security considerations and challenges for the
   Internet of Things.  Further updates of the draft were presented and
   discussed during the T2TRG meetings at IETF 96 (July 2016) and IETF
   97 (November 2016) and at the joint interim in Amsterdam (March
   2017).  This document has been reviewed by, commented on, and
   discussed extensively for a period of nearly six years by a vast
   majority of T2TRG and related group members; the number of which
   certainly exceeds 100 individuals.  It is the consensus of T2TRG that
   the security considerations described in this document should be
   published in the IRTF Stream of the RFC series.  This document does
   not constitute a standard.

2.  Motivation and background

2.1.  The Thing Lifecycle

   The lifecycle of a thing refers to the operational phases of a thing
   in the context of a given application or use case.  Figure 1 shows
   the generic phases of the lifecycle of a thing.  This generic
   lifecycle is applicable to very different IoT applications and
   scenarios.  For instance, [RFC7744] provides an overview of relevant
   IoT use cases.

   In this document, we consider a Building Automation and Control (BAC)
   system to illustrate the lifecycle and the meaning of these different
   phases.  A BAC system consists of a network of interconnected nodes
   that performs various functions in the domains of HVAC (Heating,
   Ventilating, and Air Conditioning), lighting, safety, etc.  The nodes
   vary in functionality and a large majority of them represent
   resource-constrained devices such as sensors and luminaries.  Some
   devices may be battery operated or may rely on energy harvesting.
   This requires us to also consider devices that sleep during their
   operation to save energy.  In our example, the life of a thing starts
   when it is manufactured.  Due to the different application areas
   (i.e., HVAC, lighting, or safety) nodes/things 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

   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 may be

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   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 discrete event and may stretch over an extended period.  After
   being bootstrapped, the device and the system of things are in
   operational mode and execute the functions of the BAC system.  During
   this operational phase, the device is under the control of the system
   owner and used by multiple system users.  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 be performed either locally
   or from a backend system.  Depending on the operational changes to
   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 phases 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 and rather denotes a need to replace and upgrade the
   network to the next-generation devices for additional functionality.
   Therefore, the device can be removed and re-commissioned to be used
   in a different system under a different owner thereby starting the
   lifecycle all over again.

    _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

2.2.  Security building blocks

   Security is a key requirement in any communication system.  However,
   security is an even more critical requirement in real-world IoT
   deployments for several reasons.  First, compromised IoT systems can
   not only endanger the privacy and security of a user, but can also

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   cause physical harm.  This is because IoT systems often comprise
   sensors, actuators and other connected devices in the physical
   environment of the user which could adversely affect the user if they
   are compromised.  Second, a vulnerable IoT system means that an
   attacker can alter the functionality of a device from a given
   manufacturer.  This not only affects the manufacturer's brand image,
   but can also leak information that is very valuable for the
   manufacturer (such as proprietary algorithms).  Third, the impact of
   attacking an IoT system goes beyond a specific device or an isolated
   system since compromised IoT systems can be misused at scale.  For
   example, they may be used to perform a Distributed Denial of Service
   (DDoS) attack that limits the availability of other networks and
   services.  The fact that many IoT systems rely on standard IP
   protocols allows for easier system integration, but this also makes
   standard attacks applicable to a wide number of devices deployed in
   multiple systems.  This results in new requirements regarding the
   implementation of security.

   The term security subsumes a wide range of primitives, protocols, and
   procedures.  Firstly, it includes the basic provision of security
   services that include confidentiality, authentication, integrity,
   authorization, non-repudiation, and availability along with some
   augmented services, such as duplicate detection and detection of
   stale packets (timeliness).  These security services can be
   implemented by means of 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 ensuring security in IoT
   networks, we should not only focus on the required security services,
   but also pay special attention to how these services are realized in
   the overall system and how the security functionalities are executed
   in practice.  To this end, we consider five major "building blocks"
   to analyze and classify security aspects for IoT:

   1.  IoT security architecture: refers to the system-level elements
       involved in the management of security relationships between
       things (for example, centralized or distributed).  For instance,
       a smart home could rely on a centralized key distribution center
       in charge of managing cryptographic keys, devices, users, access
       control and privacy policies.

   2.  The security model within a thing: describes the way security
       parameters, keys, processes, and applications are managed within
       a smart object.  This includes aspects such as application
       process separation, secure storage of key materials, etc.  For
       instance, some smart objects might have extremely limited
       resources and limited capabilities to protect secret keys.  In
       contrast, other devices used in critical applications, such as a

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       pacemaker, may rely on methods to protect cryptographic keys and

   3.  Security bootstrapping: denotes the process by which a thing
       securely joins an IoT system at a given location and point of
       time.  For instance, bootstrapping of a connected camera can
       include the authentication and authorization of the device as
       well as the transfer of security parameters necessary for
       operation in a given network.

   4.  Network security: describes the mechanisms applied within a
       network to ensure secure operation.  Specifically, it prevents
       attackers from endangering or modifying the expected operation of
       a smart object.  It also protects the network itself from
       malicious things.  Network security can include several
       mechanisms ranging from data link layer security, secure routing,
       and network layer security.

   5.  Application security: describes mechanisms to allow secure
       transfer of application data.  The security may be implemented at
       different layers of the Internet protocol suite.  For instance,
       assume a smart object such as an environmental sensor that is
       connected to a backend system.  Application security here can
       refer to the exchange of secure blocks of data such as
       measurements between the sensor and the backed, or it can also
       refer to a software update for the smart object.  This data is
       exchanged end-to-end independently of the underlying network
       infrastructure, for example through proxies or other store-and-
       forward mechanisms.

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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    |<-+       :
   :          +-----------+: : +-----------+ : :+-----------+          :
   :.......................: :...............: :.......................:

                 Figure 2: Overview of Security Mechanisms

   Inspired by the security framework for routing over low power and
   lossy network [RFC7416], we show an example security model of a smart
   object and illustrate how different security concepts and lifecycle
   phases map to the Internet communication stack.  Assume a centralized
   architecture in 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,

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   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.

3.  Security Threats and Managing Risk

   Security threats in related IP protocols have been analyzed in
   multiple documents including HTTPS [RFC2818], COAP [RFC7252], 6LoWPAN
   [RFC4919], ANCP [RFC5713], DNS security threats [RFC3833], IPv6 ND
   [RFC3756], and PANA [RFC4016].  In this section, we specifically
   discuss the threats that could compromise an individual thing, or the
   network as a whole.  Note that these set of threats might go beyond
   the scope of Internet protocols but we gather them here for the sake
   of completeness.  We also note that these threats can be classified
   according to either (i) the thing's lifecycle phases (when does the
   threat occur?) or (ii) the security building blocks (which
   functionality is affected by the threat?).  All these threats are
   summarized in Figure 3.

   1.  Cloning of things: During the manufacturing process of a thing,
       an untrusted factory can easily clone the physical
       characteristics, firmware/software, or security configuration of
       the thing.  Deployed things might also be compromised and their
       software reverse engineered allowing for cloning or software
       modifications.  Such a cloned thing may be sold at a cheaper
       price in the market, and yet can 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 or perform an
       attack.  One should note here, that an untrusted factory may also
       change functionality of the cloned thing, resulting in degraded
       functionality with respect to the genuine thing (thereby,
       inflicting potential damage to the reputation of the original
       thing manufacturer).  Moreover, additional functionality can be
       introduced in the cloned thing, an example of such functionality
       is 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 (for example, non-certified products) may significantly
       reduce the installation and operational costs.  The installers
       can subsequently resell the genuine things to gain further

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       financial benefits.  Another motivation may be to inflict damage
       to the reputation of 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 or if used cryptographic algorithms are not suitable for
       the envisioned lifetime of the device and the system.  After
       obtaining the keying material, the attacker might be able to
       recover the secret keys established between the communicating
       entities, 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 protocol weaknesses or 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
       attacks, for example, 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 can eavesdrop during the execution of this protocol.
       Additionally, device authentication or device authorization may
       be non-trivial, or may need support of a human decision process,
       since things usually do not have a-priori knowledge about each
       other and cannot always 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 attacks: 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 software
       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.  Similarly, devices whose software has
       not been properly maintained and updated might contain

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       vulnerabilities that might be exploited by attackers to replace
       the firmware on the device.

   6.  Extraction of private information: IoT devices (such as sensors,
       actuators, etc.) are often physically unprotected in their
       ambient environment and they could easily be captured by an
       attacker.  An attacker with physical access may then attempt to
       extract private information such as keys (for example, device's
       key, private-key, group key), sensed data (for example,
       healthcare status of a user), configuration parameters (for
       example, the Wi-Fi key), or proprietary algorithms (for example,
       algorithm performing some data analytics task).  Even when the
       data originating from a thing is encrypted, attackers can perform
       traffic analysis to deduce meaningful information which might
       compromise the privacy of the thing's owner and/or user.

   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
       the base station, thus allowing him to do manipulate 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.  For instance, 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 may subsequently be sold to
       interested parties for marketing purposes and targeted
       advertising.  In extreme cases, such information might be used to
       track dissidents in oppressive regimes.

   9.  Denial-of-Service (DoS) attack: Often things have very limited
       memory and computation capabilities.  Therefore, they are
       vulnerable to resource exhaustion attack.  Attackers can
       continuously send requests to specific things so as to deplete
       their resources.  This is especially dangerous in the Internet of
       Things since an attacker might be located in the backend and
       target resource-constrained devices that are part of a

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       constrained node network [RFC7228].  DoS attack can also be
       launched by physically jamming the communication channel.
       Network availability can also be disrupted by flooding the
       network with a large number of packets.  On the other hand,
       things compromised by attackers can be used to disrupt the
       operation of other networks or systems by means of a Distributed
       DoS (DDoS) attack.

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

              | Manufacturing    | Installation/    | Operation        |
              |                  | Commissioning    |                  |
 |System-level| Device Cloning   |Substitution      |Privacy threat    |
 |            |                  |                  |Extraction of     |
 |            |                  |                  |private inform.   |
 |Application |                  |RFC2818,          |RFC2818, Firmware |
 |Layer       |                  |RFC4016           |replacement       |
 |Transport   |                  | Eavesdropping &  |Eavesdropping     |
 |Layer       |                  | Man-in-the-middle|Man-in-the-middle |
 +------------+------------------| attack,          |------------------+
 |Network     |                  | RFC4919, RFC5713 |RFC4919,DoS attack|
 |Layer       |                  | RFC3833, RFC3756 |Routing attack    |
 |            |                  |                  |RFC3833           |
 |Physical    |                  |                  |DoS attack        |
 |Layer       |                  |                  |                  |

   Figure 3: Classification of threats according to the lifecycle phases

   Dealing with above threats and finding suitable security mitigations
   is challenging.  New threats and exploits also appear on a daily
   basis.  Therefore, the existence of proper secure product creation
   processes that allow managing and minimizing risks during the
   lifecycle of IoT devices is at least as important as being aware of
   the threats.  A non-exhaustive list of relevant processes include:

   1.  A Business Impact Analysis (BIA) assesses the consequences of the
       loss of basic security attributes: confidentiality, integrity and
       availability in an IoT system.  These consequences might include
       the impact from lost data, reduced sales, increased expenses,

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       regulatory fines, customer dissatisfaction, etc.  Performing a
       business impact analysis allows a business to determine the
       relevance of having a proper security design.

   2.  A Risk Assessment (RA) analyzes security threats to an IoT system
       while considering their likelihood and impact.  It also includes
       categorizing each of them with a risk level.  Risks classified as
       moderate or high must be mitigated, i.e., the security
       architecture should be able to deal with those threat.

   3.  A privacy impact assessment (PIA) aims at assessing the
       Personally Identifiable Information (PII) that is collected,
       processed, or used in an IoT system.  By doing so, the goal is to
       fulfill applicable legal requirements, determine risks and
       effects of manipulation and loss of PII.

   4.  Procedures for incident reporting and mitigation refer to the
       methodologies that allow becoming aware of any security issues
       that affect an IoT system.  Furthermore, this includes steps
       towards the actual deployment of patches that mitigate the
       identified vulnerabilities.

   BIA, RA, and PIA should generally be realized during the creation of
   a new IoT system or when deploying significant system/feature
   upgrades.  In general, it is recommended to re-assess them on a
   regular basis taking into account new use cases and/or threats.

4.  State-of-the-Art

   This section is organized as follows.  Section 4.1 summarizes state-
   of-the-art on IP-based IoT systems, within IETF and in other
   standardization bodies.  Section 4.2 summarizes state-of-the-art on
   IP-based security protocols and their usage.  Section 4.3 discusses
   guidelines and regulations for securing IoT as proposed by other

4.1.  IP-based IoT Protocols and Standards

   Nowadays, there exists a multitude of control protocols for IoT.  For
   BAC systems, the ZigBee standard [ZB], BACNet [BACNET], and 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] for example has defined methods
   and protocols for the efficient transmission and adaptation of IPv6
   packets over IEEE 802.15.4 networks [RFC4944].

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   The CoRE working group [WG-CoRE] has specified the Constrained
   Application Protocol (CoAP) [RFC7252].  CoAP is a RESTful protocol
   for constrained devices that is modeled after HTTP and typically runs
   over UDP to enable efficient application-level communication for

   In many smart object networks, the smart objects are dispersed and
   have intermittent reachability either because of network outages or
   because they sleep during their operational phase to save energy.  In
   such scenarios, direct discovery of resources hosted on the
   constrained server might not be possible.  To overcome this barrier,
   the CoRE working group is specifying the concept of a Resource
   Directory (RD) [ID-rd].  The Resource Directory hosts descriptions of
   resources which are located on other nodes.  These resource
   descriptions are specified as CoRE link format [RFC6690].

   While CoAP defines a standard communication protocol, a format for
   representing sensor measurements and parameters over CoAP is
   required.  The Sensor Measurement Lists (SenML) [ID-senml] is a
   specification that defines media types for simple sensor measurements
   and parameters.  It has a minimalistic design so that constrained
   devices with limited computational capabilities can easily encode
   their measurements and, at the same time, servers can efficiently
   collect large number of measurements.

   In many IoT deployments, the resource-constrained smart objects are
   connected to the Internet via a gateway that is directly reachable.
   For example, an IEEE 802.11 Access Point (AP) typically connects the
   client devices to the Internet over just one wireless hop.  However,
   some deployments of smart object networks require routing between the
   smart objects themselves.  The IETF has therefore defined the IPv6
   Routing Protocol for Low-Power and Lossy Networks (RPL) [RFC6550].
   RPL provides support for multipoint-to-point traffic from resource-
   constrained smart objects towards a more resourceful central control
   point, as well as point-to-multipoint traffic in the reverse
   direction.  It also supports point-to-point traffic between the
   resource-constrained devices.  A set of routing metrics and
   constraints for path calculation in RPL are also specified [RFC6551].

   The IPv6 over Networks of Resource-constrained Nodes (6lo) [WG-6lo]
   working group of the IETF has specified how IPv6 packets can be
   transmitted over various link layer protocols that are commonly
   employed for resource-constrained smart object networks.  There is
   also ongoing work to specify IPv6 connectivity for a Non-Broadcast
   Multi-Access (NBMA) mesh network that is formed by IEEE 802.15.4
   TimeSlotted Channel Hopping (TSCH} links [ID-6tisch].  Other link
   layer protocols for which IETF has specified or is currently
   specifying IPv6 support include Bluetooth [RFC7668], Digital Enhanced

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   Cordless Telecommunications (DECT) Ultra Low Energy (ULE) air
   interface [RFC8105], and Near Field Communication (NFC) [ID-6lonfc].

   [RFC6272] identifies IP protocols that can be used in smart grid
   environments.  It gives advice to smart grid network designers on how
   they can decide on a profile of the Internet protocol suite for smart
   grid networks.

   JavaScript Object Notation (JSON) is a lightweight text
   representation format for structured data [RFC7159].  It is often
   used for transmitting serialized structured data over the network.
   IETF has defined specifications for encoding public keys, signed
   content, and claims to be transferred between two parties as JSON
   objects.  They are referred to as JSON Web Keys (JWK) [RFC7517], JSON
   Web Signatures (JWS) [RFC7515] and JSON Web Token (JWT) [RFC7519].

   An alternative to JSON, Concise Binary Object Representation (CBOR)
   [RFC7049] is a concise binary data format that is used for
   serialization of structured data.  It is designed for resource-
   constrained nodes and therefore it aims to provide a fairly small
   message size with minimal implementation code, and extensibility
   without the need for version negotiation.  CBOR Object Signing and
   Encryption (COSE) [RFC8152] specifies how to encode public keys and
   signed content with CBOR.

   The Light-Weight Implementation Guidance (LWIG) working group
   [WG-LWIG] is collecting experiences from implementers of IP stacks in
   constrained devices.  The working group has already produced
   documents such as RFC7815 [RFC7815] which defines how a minimal
   Internet Key Exchange Version 2 (IKEv2) initiator can be implemented.

   The Thing-2-Thing Research Group (T2TRG) [RG-T2TRG] is investigating
   the remaining research issues that need to be addressed to quickly
   turn the vision of IoT into a reality where resource-constrained
   nodes can communicate with each other and with other more capable
   nodes on the Internet.

   Additionally, industry alliances and other standardization bodies are
   creating constrained IP protocol stacks based on the IETF work.  Some
   important examples of this include:

   1.  Thread [Thread]: Specifies the Thread protocol that is intended
       for a variety of IoT devices.  It is an IPv6-based network
       protocol that runs over IEEE 802.15.4.

   2.  Industrial Internet Consortium [IIoT]: The consortium defines
       reference architectures and security frameworks for development,

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       adoption and widespread use of Industrial Internet technologies
       based on existing IETF standards.

   3.  Internet Protocol for Smart Objects IPSO [IPSO]: The alliance
       specifies a common object model that enables application software
       on any device to interoperate with other conforming devices.

   4.  OneM2M [OneM2M]: The standards body defines technical and API
       specifications for IoT devices.  It aims to create a service
       layer that can run on any IoT device hardware and software.

   5.  Open Connectivity Foundation (OCF) [OCF]: The foundation develops
       standards and certifications primarily for IoT devices that use
       Constrained Application Protocol (CoAP) as the application layer

   6.  Fairhair Alliance [Fairhair]: Specifies an IoT middleware to
       enable interoperability between different application standards
       used in building automation and lighting systems.

   7.  OMA LWM2M [LWM2M]: OMA Lightweight M2M is a standard from the
       Open Mobile Alliance for M2M and IoT device management.  LWM2M
       relies on CoAP as the application layer protocol and uses a
       RESTful architecture for remote management of IoT devices.

4.2.  Existing IP-based Security Protocols and Solutions

   There are thee main security objectives for IoT networks: 1.
   protecting the IoT network from attackers.  2. protecting IoT
   applications and thus, the things and users.  3. protecting the rest
   of the Internet and other things from attacks that use compromised
   things as an attack platform.

   In the context of the IP-based IoT deployments, consideration of
   existing Internet security protocols is important.  There are a wide
   range of specialized as well as general-purpose security solutions
   for the Internet domain such as IKEv2/IPsec [RFC7296], TLS [RFC5246],
   DTLS [RFC6347], HIP [RFC7401], PANA [RFC5191], and EAP [RFC3748].

   There is ongoing work to define an authorization and access-control
   framework for resource-constrained nodes.  The Authentication and
   Authorization for Constrained Environments (ACE) [WG-ACE] working
   group is defining a solution to allow only authorized access to
   resources that are hosted on a smart object server and are identified
   by a URI.  The current proposal [ID-aceoauth] is based on the OAuth
   2.0 framework [RFC6749] and it comes with profiles intended for
   different communication scenarios, e.g.  DTLS Profile for

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   Authentication and Authorization for Constrained Environments

   The CoAP base specification [RFC7252] provides a description of how
   DTLS can be used for securing CoAP.  It proposes three different
   modes for using DTLS: the PreSharedKey mode, where nodes have pre-
   provisioned keys for initiating a DTLS session with another node,
   RawPublicKey mode, where nodes have asymmetric-key pairs but no
   certificates to verify the ownership, and Certificate mode, where
   public keys are certified by a certification authority.  An IoT
   implementation profile [RFC7925] is defined for TLS version 1.2 and
   DTLS version 1.2 that offers communication security for resource-
   constrained nodes.

   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

   OSCOAP [ID-OSCOAP] is a proposal that protects CoAP messages by
   wrapping them in the CBOR Object Signing and Encryption (COSE)
   [RFC8152] format.  Thus, OSCOAP falls in the category of object
   security and it can be applied wherever CoAP can.  The advantage of
   OSCOAP compared with DTLS resides in some more flexibility when
   dealing with e2e security as it will be discussed in
   Section Section 5.1.3.

   The Automated Certificate Management Environment (ACME) [WG-ACME]
   working group is specifying conventions for automated X.509
   certificate management.  This includes automatic validation of
   certificate issuance, certificate renewal, and certificate
   revocation.  While the initial focus of working group is on domain
   name certificates (as used by web servers), other uses in some IoT
   deployments is possible.

   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 for secure payload delivery.  Currently, there are
   also ongoing efforts to create a HIP variant coined Diet HIP
   [ID-HIP-DEX] that takes constrained networks and nodes into account
   at the authentication and key exchange level.

   Migault et al.  [ID-dietesp] are working on a compressed version of
   IPsec so that it can easily be used by resource-constrained IoT

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   devices.  They rely on the Internet Key Exchange Protocol version 2
   (IKEv2) for negotiating the compression format.

   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.

   Figure 4 depicts the relationships between the discussed protocols in
   the context of the security terminology introduced in Section 2.

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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   ||<-+       :
 :          +===========+=====+===========+=====+===========+          :
 :.......................:  :...............:  :.......................:

        Figure 4: Relationships between IP-based security protocols

4.3.  IoT Security Guidelines

   Attacks on and from IoT devices have become common in the last years,
   for instance, large scale Denial of Service (DoS) attacks on the
   Internet Infrastructure from compromised IoT devices.  This fact has
   prompted many different standards bodies and consortia to provide
   guidelines for developers and the Internet community at large to

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   build secure IoT devices and services.  A subset of the different
   guidelines and ongoing projects are as follows:

   1.   GSMA IoT security guidelines [GSMAsecurity]: GSMA has published
        a set of security guidelines for the benefit of new IoT product
        and service providers.  The guidelines are aimed at device
        manufacturers, service providers, developers and network
        operators.  An enterprise can complete an IoT Security Self-
        Assessment to demonstrate that its products and services are
        aligned with the security guidelines of the GSMA.

   2.   BITAG Internet of Things (IoT) Security and Privacy
        Recommendations [BITAG]: Broadband Internet Technical Advisory
        Group (BITAG) has also published recommendations for ensuring
        security and privacy of IoT device users.  BITAG observes that
        many IoT devices are shipped from the factory with software that
        is already outdated and vulnerable.  The report also states that
        many devices with vulnerabilities will not be fixed either
        because the manufacturer does not provide updates or because the
        user does not apply them.  The recommendations include that IoT
        devices should function without cloud and Internet connectivity,
        and that all IoT devices should have methods for automatic
        secure software updates.

   3.   CSA New Security Guidance for Early Adopters of the IoT [CSA]:
        The Cloud Security Alliance (CSA) recommendations for early
        adopters of IoT encourages enterprises to implement security at
        different layers of the protocol stack.  It also recommends
        implementation of an authentication/authorization framework for
        IoT deployments.  A complete list of recommendations is
        available in the report [CSA].

   4.   U.S.  Department of Homeland Security [DHS]: DHS has put forth
        six strategic principles that would enable IoT developers,
        manufacturers, service providers and consumers to maintain
        security as they develop, manufacture, implement or use network-
        connected IoT devices.

   5.   NIST [NIST-Guide]: The NIST special publication urges enterprise
        and US federal agencies to address security throughout the
        systems engineering process.  The publication builds upon the
        ISO/IEC 15288 standard and augments each process in the system
        lifecycle with security enhancements.

   6.   NIST [nist_lightweight_project]: NIST is running a project on
        lightweight cryptography with the purpose of: (i) identifying
        application areas for which standard cryptographic algorithms
        are too heavy, classifying them according to some application

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        profiles to be determined; (ii) determining limitations in those
        existing cryptographic standards; and (iii) standardizing
        lightweight algorithms that can be used in specific application

   7.   OWASP [OWASP]: Open Web Application Security Project (OWASP)
        provides security guidance for IoT manufactures, developers and
        consumers.  OWASP also includes guidelines for those who intend
        to test and analyze IoT devices and applications.

   8.   IoT Security foundation [IoTSecFoundation]: IoT security
        foundation has published a document that enlists various
        considerations that need to be taken into account when
        developing IoT applications.  For example, the document states
        that IoT devices could use hardware-root of trust to ensure that
        only authorized software runs on the devices.

   9.   NHTSA [NHTSA]: The US National Highway Traffic Safety
        Administration provides a set of non-binding guidance to the
        automotive industry for improving the cyber security of
        vehicles.  While some of the guidelines are general, the
        document provides specific recommendations for the automotive
        industry such as how various automotive manufacturer can share
        cyber security vulnerabilities discovered.

   10.  Best Current Practices (BCP) for IoT devices [ID-Moore]: This
        document provides a list of minimum requirements that vendors of
        Internet of Things (IoT) devices should to take into account
        while developing applications, services and firmware updates in
        order to reduce the frequency and severity of security incidents
        that arise from compromised IoT devices.

   11.  ENISA [ENISA_ICS]: The European Union Agency for Network and
        Information Security published a document on communication
        network dependencies for ICS/SCADA systems in which security
        vulnerabilities, guidelines and general recommendations are

   Other guideline and recommendation documents may exist or may later
   be published.  This list should be considered non-exhaustive.
   Despite the acknowledgment that security in the Internet is needed
   and the existence of multiple guidelines, the fact is that many IoT
   devices and systems have very limited security.  There are multiple
   reasons for this.  For instance, some manufactures focus on
   delivering a product without paying enough attention to security.
   This may be because of lack of expertise or limited budget.  However,
   the deployment of such insecure devices poses a severe threat on the
   privacy and safety of users.  The vast amount of devices and their

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   inherent mobile nature also implies that an initially secure system
   can become insecure if a compromised device gains access to the
   system at some point in time.  Even if all other devices in a given
   environment are secure, this does not prevent external (passive)
   attacks caused by insecure devices.

   Recently the Federal Communications Commission (FCC) [FCC] has stated
   the need for additional regulation of IoT systems.  FCC identifies
   this as a missing component, especially for Federal Information
   Systems (FIS).  Today, security in the US FIS is regulated according
   to Federal Information Security Management Act (FISMA).  From this
   law, NIST has derived a number of new documents to categorize FIS and
   determine minimum security requirements for each category.  These
   minimum security requirements are specified in NIST SP 800-53r4

   Even with strong regulations in place, the question remains as to how
   such regulations can be applied in practice to non-federal
   deployments, such as industrial, homes, offices, or smart cites.
   Each of them exhibits unique features, involves very diverse types of
   users, has different operational requirements, and combines IoT
   devices from multiple manufacturers.  Future regulations should
   therefore consider such diverse deployment scenarios.

5.  Challenges for a Secure IoT

   In this section, we take a closer look at the various security
   challenges in the operational and technical features of IoT and then
   discuss how existing Internet security protocols cope with these
   technical and conceptual challenges through the lifecycle of a thing.
   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 and
   challenges in some IoT design areas rather than giving an abstract
   discussion.  In this regard, the discussion handles issues that are
   most important from the authors' perspectives.

5.1.  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.

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5.1.1.  Resource Constraints

   IoT deployments are often characterized by lossy and low-bandwidth
   communication channels.  IoT devices are also often constrained in
   terms of CPU, memory, and energy budget available [RFC7228].  These
   characteristics directly impact the threats to and the design of
   security protocols for the IoT domain.  First, the use of small
   packets, for example, IEEE 802.15.4 supports 127-byte sized packets
   at the physical layer, may result in fragmentation of larger packets
   required by security protocols.  This may open new attack vectors for
   state exhaustion DoS attacks, which is especially tragic, for
   example, if the fragmentation is caused by large key exchange
   messages of security protocols.  Moreover, packet 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, for example,
   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
   crypto primitives such as public-key cryptography as used in most
   Internet security standards.  This is especially true if the basic
   crypto blocks 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
   Elliptic Curve Cryptography (ECC) [RFC5246], [RFC5903], [RFC7401],
   and [ID-HIP-DEX].  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

   A further fundamental need refers to the limited energy budget
   available to IoT nodes.  Careful protocol (re)design and usage is

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   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.

5.1.2.  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 (for example, 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 delay the establishment of state at the responding host
   until the address of the initiating host is verified.  The
   effectiveness of these defenses strongly depend 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 (for example, 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 (for
   example, 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
   misconfiguration or malfunctioning things.

5.1.3.  End-to-end security, protocol translation, and the role of

   The term end-to-end security often has multiple interpretations.
   Here, we consider end-to-end security in the context end-to-end IP
   connectivity, from a sender to a receiver.  Services such as
   confidentiality and integrity protection on packet data, message
   authentication codes or encryption are typically used to provide end-
   to-end security.  These protection methods render the protected parts
   of the packets immutable as rewriting is either not possible because

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   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.

   Protocols for constrained IoT networks are not exactly identical to
   their larger Internet counterparts for efficiency and performance
   reasons.  Hence, more or less subtle differences between protocols
   for constrained IoT networks and Internet protocols will remain.
   While these differences can be bridged with protocol translators at
   middleboxes, they may become major obstacles if end-to-end security
   measures between IoT devices and Internet hosts are needed.

   If access to data or messages by the middleboxes is required or
   acceptable, then a diverse set of approaches for handling such a
   scenario are available.  Note that some of these approaches affect
   the meaning of end-to-end security in terms of integrity and
   confidentiality since the middleboxes will be able to either decrypt
   or modify partially the exchanged messages:

   1.  Sharing credentials with middleboxes enables them to transform
       (for example, decompress, convert, etc.) packets and re-apply the
       security measures after transformation.  This method abandons
       end-to-end security and is only applicable to simple scenarios
       with a rudimentary security model.

   2.  Reusing the Internet wire format for IoT makes conversion between
       IoT and Internet protocols unnecessary.  However, it can lead to
       poor performance in some use cases because IoT specific
       optimizations (for example, stateful or stateless compression)
       are not possible.

   3.  Selectively protecting vital and immutable packet parts with a
       message authentication code or with encryption requires a careful
       balance between performance and security.  Otherwise this
       approach might either result in poor performance or poor security
       depending on which parts are selected for protection, where they
       are located in the original packet, and how they are processed.
       [ID-OSCOAP] proposes a solution in this direction by encrypting
       and integrity protecting most of the message fields except those
       parts that a middlebox needs to read or change.

   4.  Homomorphic encryption techniques can be used in the middlebox to
       perform certain operations.  However, this is limited to data
       processing involving arithmetic operations.  Furthermore,
       performance of existing libraries, for example, SEAL [SEAL] is
       still too limited and it is is not widely applicable yet.

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   5.  Message authentication codes that sustain transformation can be
       realized by considering the order of transformation and
       protection (for example, by creating a signature before
       compression so that the gateway can decompress the packet without
       recalculating the signature).  Such an approach enables IoT
       specific optimizations but is more complex and may require
       application-specific transformations before security is applied.
       Moreover, the usage of encrypted or integrity-protected data
       prevents middleboxes from transforming packets.

   6.  Mechanisms based on object security can bridge the protocol
       worlds, but still require that the two worlds use the same object
       security formats.  Currently the object security format based on
       CBOR Object Signing and Encryption (COSE) [RFC8152] (IoT
       protocol) is different from JSON Object Signing and Encryption
       (JOSE) [RFC7520] or Cryptographic Message Syntax (CMS) [RFC5652].
       Legacy devices relying on traditional Internet protocols will
       need to update to the newer protocols for constrained
       environments to enable real end-to-end security.  Furthermore,
       middleboxes do not have any access to the data and this approach
       does not prevent an attacker from modifying relevant fields in

   To the best of our knowledge, none of the mentioned security
   approaches that focus on the confidentiality and integrity of the
   communication exchange between two IP end-points provide the perfect
   solution in this problem space.

   We finally note that end-to-end security can also be considered in
   the context of availability: making sure that the messages are
   delivered.  In this case, the end-points cannot control this, but the
   middleboxes play a fundamental role to make sure that exchanged
   messages are not dropped, for example, due to a DDoS attack.

5.1.4.  New network architectures and paradigm

   There is a multitude of new link layer protocols that aim to address
   the resource-constrained nature of IoT devices.  For example, the
   IEEE 802.11 ah [IEEE802ah] has been specified for extended range and
   lower energy consumption to support Internet of Things (IoT) devices.
   Similarly, Low-Power Wide-Area Network (LPWAN) protocols such as LoRa
   [lora], Sigfox [sigfox], NarrowBand IoT (NB-IoT) [nbiot] are all
   designed for resource-constrained devices that require long range and
   low bit rates.  While these protocols allow IoT devices to conserve
   energy and operate efficiently, they also add additional security
   challenges.  For example, the relatively small MTU can make security
   handshakes with large X509 certificates a significant overhead.  At
   the same time, new communication paradigms also allow IoT devices to

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   communicate directly amongst themselves with or without support from
   the network.  This communication paradigm is also referred to as
   Device-to-Device (D2D) or Machine-to-Machine (M2M) or Thing-to-Thing
   (T2T) communication.  D2D is primarily driven by network operators
   that want to utilize short range communication to improve the network
   performance and for supporting proximity based service

5.2.  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 in an IoT
   network.  This aspect is further elaborated and discussed in the
   T2TRG draft on bootstrapping [ID-bootstrap].

5.3.  Operational Challenges

   After the bootstrapping phase, the system enters the operational
   phase.  During the operational phase, things can use the state
   information created during the bootstrapping phase in order to
   exchange information securely.  In this section, we discuss the
   security challenges during the operational phase.  Note that many of
   the challenges discussed in Section 5.1 apply during the operational

5.3.1.  Group Membership and Security

   Group key negotiation is an important security service for IoT
   communication patterns in which a thing sends some data to multiple
   things or data flows from multiple things towards a thing.  All
   discussed protocols only cover unicast communication and therefore,
   do not focus on group-key establishment.  This applies in particular
   to (D)TLS and IKEv2.  Thus, a solution is required in this area.  A
   potential solution might be to use the Diffie-Hellman keys - that are
   used in IKEv2 and HIP to setup a secure unicast link - for group
   Diffie-Hellman key-negotiations.  However, Diffie-Hellman is a
   relatively heavy solution, especially if the group is large.

   Conceptually, solutions that provide secure group communication at
   the network layer (IPsec/IKEv2, HIP/Diet HIP) may have an advantage
   in terms of the cryptographic overhead when compared to application-
   focused security solutions (TLS/ DTLS).  This is due to the fact that
   application-focused solutions require cryptographic operations per
   group application, whereas network layer approaches may allow sharing
   secure group associations between multiple applications (for example,
   for neighbor discovery and routing or service discovery).  Hence,
   implementing shared features lower in the communication stack can
   avoid redundant security measures.  In the case of OSCOAP, it
   provides security for CoAP group communication as defined in RFC7390,

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   i.e., based on multicast IP.  If the same security association is
   reused for each application, then this solution does not seem to have
   more cryptographic overhead compared to IPsec.

   Several group key solutions have been developed by the MSEC working
   group [WG-MSEC] of the IETF.  The MIKEY architecture [RFC4738] is one
   example.  While these solutions are specifically tailored for
   multicast and group broadcast applications in the Internet, they
   should also be considered as candidate solutions for group key
   agreement in IoT.  The MIKEY architecture for example 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 IoT environment, where the
   choice of one or several coordinators and the management of the group
   key is not trivial.

5.3.2.  Mobility and IP Network Dynamics

   It is expected that many things (for example, 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] and [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 [RFC8046].  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 and can use the same
   mechanisms.  TLS and DTLS do not have native 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 the nodes operate.  In many cases,
   mobility supported by means of a mobile gateway may suffice to enable
   mobile IoT networks, such as body sensor networks.

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5.4.  Software update

   IoT devices have a reputation for being insecure, and yet, they are
   expected to stay functional 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.

   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 IoT devices is simply a binary blob without
   any source code available.  Since the complete source code is not
   available, no patches can be written for that piece of code.  Lastly
   Schneier points out that even when updates are available, users
   generally have to manually download and install them.  However, users
   are never alerted about security updates and at many times do not
   have the necessary expertise to manually administer the required

   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 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.

   Powerful IoT devices that run general purpose operating systems can
   make use of sophisticated software update mechanisms known from the
   desktop world.  However, resource-constrained devices that do not
   have any operating system and are typically not equipped with a
   memory management unit or similar tools require more specialized

   It is important to mention previous and ongoing work in the area of
   secure software and firmware updates at the IETF.  [RFC4108]
   describes how Cryptographic Message Syntax (CMS) [RFC5652] can be
   used to protect firmware packages.  The IAB has 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

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   have been documented [iotsu].  Finally, a new working group called
   Firmware UpDate (fud) [WG-FUD] is currently being chartered at the
   IETF.  The working group aims to standardize a new version [RFC4108]
   that reflects the best current practices for firmware update based on
   experience with IoT deployments.  It will specifically work on
   describing an IoT firmware update architecture and specifying a
   manifest format that contains meta-data about the firmware update

5.5.  Verifying device behavior

   Users often have a false sense of privacy when using new 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 verify its
   operational behavior.  For instance, the user might want to know if
   the device is connecting to the server of the manufacturer for any
   reason.  This feature - connected to the manufacturer's server - may
   be necessary in some scenarios, such as during the initial
   configuration of the device.  However, the user should be kept aware
   of the data that the device is sending back to the vendor.  For
   example, the user might want to know if his/her TV is 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 IoT devices 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

   Manufacturer Usage Description (MUD) files [ID-MUD] are perhaps a
   first step towards implementation of such a monitoring service.  The
   idea behind MUD files is relatively simple: IoT devices would
   disclose the location of their MUD file to the network during
   installation.  The network can then retrieve those files, and learn
   about the intended behavior of the devices stated by the device
   manufacturer.  A network monitoring service could then warn the user/
   owner of devices if they don't behave as expected.

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5.6.  End-of-Life

   Like all commercial devices, IoT devices have a given useful
   lifetime.  The term end-of-life (EOL) is used by vendors or network
   operators to indicate the point of time in which they limit or end
   support for the IoT product.  This may be planned or unplanned (for
   example when the vendor or manufacturer goes bankrupt or when a
   network operator moves to a different type of networking technology).
   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 the
   official EOL.  Admittedly it is not easy for an average user to
   install and configure their devices on their own.  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 is EOL.

5.7.  Testing: bug hunting and vulnerabilities

   Given that IoT devices often have inadvertent vulnerabilities, both
   users and developers would want to perform extensive testing on their
   IoT devices, networks, and systems.  Nonetheless, since the devices
   are resource-constrained and manufactured by multiple vendors, some
   of them very small, devices might be shipped with very limited
   testing, so that bugs can remain and can be exploited at a later
   stage.  This leads to two main types of challenges:

   1.  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 to give end users the confidence that
       the purchased devices are robust.

   2.  It is also an open question how the combination of devices from
       multiple vendors might actually lead to dangerous network
       configurations, for example, if combination of specific devices
       can trigger unexpected behavior.

5.8.  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
   happens, it will 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, for example, 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

   The above scenario becomes more urgent when we consider the so called
   "harvest and decrypt" attack in which an attacker can start to
   harvest (store) encrypted data today, before a quantum-computer is
   available, and decrypt it years later, once a quantum computer is

   This situation would require us to move to quantum-resistant
   alternatives, in particular, for those functionalities involving key
   exchange, public-key encryption and signatures.  [ID-c2pq] describes
   when quantum computers may become widely available and what steps are
   necessary for transition to cryptographic algorithms that provide
   security even in presence of quantum computers.  While 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 computational 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.

5.9.  Privacy protection

   Users will be surrounded by hundreds of connected IoT devices.  Even
   if the communication links are encrypted and protected, information
   about the users might be collected for different purposes affecting
   their privacy.  In [Ziegeldorf], privacy in IoT is defined as the
   threefold guarantee to the user for: 1. awareness of privacy risks
   imposed by smart things and services surrounding the data subject, 2.
   individual control over the collection and processing of personal
   information by the surrounding smart things, 3. awareness and control
   of subsequent use and dissemination of personal information by those
   entities to any entity outside the subject's personal control sphere.

   Based on this definition, several privacy threats and challenges have
   been documented [Ziegeldorf] and [RFC6973]:

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   1.  Identification - refers to the identification of the users and
       their objects.

   2.  Localization - relates to the capability of locating a user and
       even tracking them.

   3.  Profiling - is about creating a profile of the user and their

   4.  Interaction - occurs when a user has been profiled and a given
       interaction is preferred, presenting (for example, visually) some
       information that discloses private information.

   5.  Lifecycle transitions - take place when devices are, for example,
       sold without properly removing private data.

   6.  Inventory attacks - happen if specific information about (smart)
       objects in possession of a user is disclosed.

   7.  Linkage - is about when information of two of more IoT systems is
       combined so that a broader view on the personal data is created.

   When IoT systems are deployed, the above issues should be considered
   to ensure that private data remains private.  How to achieve this in
   practice is still an area of ongoing research.

5.10.  Data leakage

   Many IoT devices are resource-constrained and often deployed in
   unattended environments.  Some of these devices can also be purchased
   off-the-shelf or online without any credential-provisioning process.
   Therefore, an attacker can have direct access to the device and apply
   advanced techniques to retrieve information that a traditional black
   box model does not consider.  Example of those techniques are side-
   channel attacks or code disassembly.  By doing this, the attacker can
   try to retrieve data such as:

   1.  long term keys that might be used to perform attacks on devices
       deployed in other locations.

   2.  source code that might allow the attacker to determine bugs or
       find exploits to perform other types of attacks.  The attacker
       might also just sell the source code.

   3.  proprietary algorithms that could be counterfeited or modified to
       perform advanced attacks.

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   Protection against such data leakage patterns is not trivial since
   devices are inherently resource-constrained.  An open question is
   whether there are any viable techniques to protect IoT devices and
   the data in the devices in such an adversarial model.

5.11.  Trustworthy IoT Operation

   Flaws in the design and implementation of a secure IoT device and
   network can lead to security vulnerabilities.  For instance, a flaw
   is the distribution of an Internet-connected IoT device in which a
   default password is used in all devices.  Many IoT devices can be
   found in the Internet by means of tools such as Shodan [shodan], and
   if they have any vulnerability, it can then be exploited at scale,
   for example, to launch DDoS attacks.  This is not fiction but reality
   as Dyn, a mayor DNS was attacked by means of a DDoS attack originated
   from a large IoT botnet composed of thousands of compromised IP-
   cameras [dyn-attack].  Open questions in this area are:

   1.  How to prevent large scale vulnerabilities in IoT devices?

   2.  How to prevent attackers from exploiting vulnerabilities in IoT
       devices at large scale?

   3.  If the vulnerability has been exploited, how do we stop a large
       scale attack before any damage is caused?

   Some ideas are being explored to address this issue.  One of this
   approaches refers to the specification of Manufacturer Usage
   Description (MUD) files [ID-MUD].  As explained earlier, this
   proposal requires IoT devices to disclose the location of their MUD
   file to the network during installation.  The network can then (i)
   retrieve those files, (ii) learn from the manufacturers the intended
   usage of the devices, for example, which services they require to
   access, and then (iii) create suitable filters such as firewall

6.  Conclusions and Next Steps

   This Internet Draft provides IoT security researchers, system
   designers and implementers with an overview of both operational and
   security requirements in the IP-based Internet of Things.  We discuss
   a general threat model, threats, state-of-the-art, and security

   Although plenty of steps have been realized during the last few years
   (summarized in Section 4.1) and many organizations are publishing
   general recommendations (Section 4.3) describing how IoT should be
   secured, there are many challenges ahead that require further

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   attention.  Challenges of particular importance are bootstrapping of
   security, group security, secure software updates, long-term security
   and quantum-resistance, privacy protection, data leakage prevention -
   where data could be cryptographic keys, personal data, or even
   algorithms - and ensuring trustworthy IoT operation.  All these
   problems are important; however, different deployment environments
   have different operational and security demands.  Thus, a potential
   approach is the definition and standardization of security profiles,
   each with specific mitigation strategies according to the risk
   assessment associated with the security profile.  Such an approach
   would ensure minimum security capabilities in different environments
   while ensuring interoperability.

7.  Security Considerations

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

8.  IANA Considerations

   This document contains no request to IANA.

9.  Acknowledgments

   We gratefully acknowledge feedback and fruitful discussion with
   Tobias Heer, Robert Moskowitz, Thorsten Dahm, Hannes Tschofenig,
   Carsten Bormann, Barry Raveendran, Ari Keranen, Goran Selander, Fred
   Baker and Eliot Lear.  We acknowledge the additional authors of the
   previous version of this document Sye Loong Keoh, Rene Hummen and
   Rene Struik.

10.  Informative References

              "Opinion 8/2014 on the on Recent Developments on the
              Internet of Things", Web
              recommendation/files/2014/wp223_en.pdf, n.d..

   [AUTO-ID]  "AUTO-ID LABS", Web, September

   [BACNET]   "BACnet", Web, February 2011.

   [BITAG]    "Internet of Things (IoT) Security and Privacy
              Recommendations", Web

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   [cctv]     "Backdoor In MVPower DVR Firmware Sends CCTV Stills To an
              Email Address In China", Web
              email-address-in-china, n.d..

   [CSA]      "Security Guidance for Early Adopters of the Internet of
              Things (IoT)", Web
              gs.pdf, n.d..

   [DALI]     "DALI", Web, February

   [DHS]      "Strategic Principles For Securing the Internet of Things
              (IoT)", Web
              2016-1115-FINAL....pdf, n.d..

              "Dyn Analysis Summary Of Friday October 21 Attack", Web
              october-21-attack/, n.d..

              "Communication network dependencies for ICS/SCADA
              Systems", European Union Agency For Network And
              Information Security , February 2017.

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

              "Fairhair Alliance", Web https://www.fairhair-
    , n.d..

   [FCC]      "Federal Communications Comssion Response 12-05-2016",
              FCC , February 2016.

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              "FTC Report on Internet of Things Urges Companies to Adopt
              Best Practices to Address Consumer Privacy and Security
              Risks", Web
              companies-adopt-best-practices, n.d..

              "GSMA IoT Security Guidelines", Web
              iot-security-guidelines/, n.d..

              Choi, Y., Hong, Y., Youn, J., Kim, D., and J. Choi,
              "Transmission of IPv6 Packets over Near Field
              Communication", draft-ietf-6lo-nfc-07 (work in progress),
              June 2017.

              Thubert, P., "An Architecture for IPv6 over the TSCH mode
              of IEEE 802.15.4", draft-ietf-6tisch-architecture-12 (work
              in progress), August 2017.

              Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
              L. Seitz, "Datagram Transport Layer Security (DTLS)
              Profile for Authentication and Authorization for
              Constrained Environments (ACE)", draft-ietf-ace-dtls-
              authorize-01 (work in progress), July 2017.

              Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments (ACE)", draft-ietf-ace-oauth-
              authz-07 (work in progress), August 2017.

              Sarikaya, B., Sethi, M., and A. Sangi, "Secure IoT
              Bootstrapping: A Survey", draft-sarikaya-t2trg-
              sbootstrapping-03 (work in progress), February 2017.

   [ID-c2pq]  Hoffman, P., "The Transition from Classical to Post-
              Quantum Cryptography", draft-hoffman-c2pq-02 (work in
              progress), August 2017.

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              Park, S., Kim, K., Haddad, W., Chakrabarti, S., and J.
              Laganier, "IPv6 over Low Power WPAN Security Analysis",
              draft-daniel-6lowpan-security-analysis-05 (work in
              progress), March 2011.

              Migault, D., Guggemos, T., and C. Bormann, "Diet-ESP: a
              flexible and compressed format for IPsec/ESP", draft-mglt-
              6lo-diet-esp-02 (work in progress), July 2016.

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

              Moore, K., Barnes, R., and H. Tschofenig, "Best Current
              Practices for Securing Internet of Things (IoT) Devices",
              draft-moore-iot-security-bcp-01 (work in progress), July

   [ID-MUD]   Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
              Description Specification", draft-ietf-opsawg-mud-10 (work
              in progress), September 2017.

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

              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security of CoAP (OSCOAP)", draft-ietf-core-
              object-security-04 (work in progress), July 2017.

   [ID-rd]    Shelby, Z., Koster, M., Bormann, C., Stok, P., and C.
              Amsuess, "CoRE Resource Directory", draft-ietf-core-
              resource-directory-11 (work in progress), July 2017.

              Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Media Types for Sensor Measurement Lists
              (SenML)", draft-ietf-core-senml-10 (work in progress),
              July 2017.

              Williams, M. and J. Barrett, "Mobile DTLS", draft-barrett-
              mobile-dtls-00 (work in progress), March 2009.

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Internet-Draft                IoT Security                September 2017

              "Status of Project IEEE 802.11ah, IEEE P802.11- Task Group
              AH-Meeting Update.",

   [IIoT]     "Industrial Internet Consortium",
              Web, n.d..

              "Establishing Principles for Internet of Things Security",
              principles-for-internet-of-things-security/, n.d..

   [iotsu]    "Patching the Internet of Things: IoT Software Update
              Workshop 2016", Web
              of-things-iot-software-update-workshop-2016/, n.d..

   [IPSO]     "IPSO Alliance", Web, n.d..

   [lora]     "LoRa - Wide Area Networks for IoT", Web https://www.lora-
    , n.d..

   [LWM2M]    "OMA LWM2M", Web
              lightweight-m2m-lwm2m, n.d..

   [nbiot]    "NarrowBand IoT", Web
    , n.d..

   [NHTSA]    "Cybersecurity Best Practices for Modern Vehicles", Web
              pdf/812333_CybersecurityForModernVehicles.pdf, n.d..

              Ross, R., McEvilley, M., and J. Oren, "Systems Security
              Engineering", Web
              NIST.SP.800-160.pdf, n.d..

              "Security and Privacy Controls for Federal Information
              Systems and Organizations",
              Web, n.d..

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Internet-Draft                IoT Security                September 2017

              "NIST lightweight Project", Web
              sonmez-turan-presentation-lwc2016.pdf, n.d..

   [OCF]      "Open Connectivity Foundation",
              Web, n.d..

   [OneM2M]   "OneM2M", Web, n.d..

   [OWASP]    "IoT Security Guidance",

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000, <https://www.rfc-

   [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,

   [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,

   [RFC3833]  Atkins, D. and R. Austein, "Threat Analysis of the Domain
              Name System (DNS)", RFC 3833, DOI 10.17487/RFC3833, August
              2004, <>.

   [RFC4016]  Parthasarathy, M., "Protocol for Carrying Authentication
              and Network Access (PANA) Threat Analysis and Security
              Requirements", RFC 4016, DOI 10.17487/RFC4016, March 2005,

   [RFC4108]  Housley, R., "Using Cryptographic Message Syntax (CMS) to
              Protect Firmware Packages", RFC 4108,
              DOI 10.17487/RFC4108, August 2005, <https://www.rfc-

   [RFC4555]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol
              (MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,

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Internet-Draft                IoT Security                September 2017

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

   [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, <https://www.rfc-

   [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,

   [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,

   [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, <>.

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

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,

   [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, <>.

   [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, <https://www.rfc-

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Internet-Draft                IoT Security                September 2017

   [RFC6272]  Baker, F. and D. Meyer, "Internet Protocols for the Smart
              Grid", RFC 6272, DOI 10.17487/RFC6272, June 2011,

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <>.

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012, <https://www.rfc-

   [RFC6551]  Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
              and D. Barthel, "Routing Metrics Used for Path Calculation
              in Low-Power and Lossy Networks", RFC 6551,
              DOI 10.17487/RFC6551, March 2012, <https://www.rfc-

   [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, <https://www.rfc-

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013, <https://www.rfc-

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <>.

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Internet-Draft                IoT Security                September 2017

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014, <https://www.rfc-

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

   [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, <>.

   [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,

   [RFC7416]  Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
              and M. Richardson, Ed., "A Security Threat Analysis for
              the Routing Protocol for Low-Power and Lossy Networks
              (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015, <https://www.rfc-

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,

   [RFC7520]  Miller, M., "Examples of Protecting Content Using JSON
              Object Signing and Encryption (JOSE)", RFC 7520,
              DOI 10.17487/RFC7520, May 2015, <https://www.rfc-

   [RFC7668]  Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
              Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
              Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,

Garcia-Morchon, et al.   Expires March 23, 2018                [Page 43]

Internet-Draft                IoT Security                September 2017

   [RFC7696]  Housley, R., "Guidelines for Cryptographic Algorithm
              Agility and Selecting Mandatory-to-Implement Algorithms",
              BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,

   [RFC7744]  Seitz, L., Ed., Gerdes, S., Ed., Selander, G., Mani, M.,
              and S. Kumar, "Use Cases for Authentication and
              Authorization in Constrained Environments", RFC 7744,
              DOI 10.17487/RFC7744, January 2016, <https://www.rfc-

   [RFC7815]  Kivinen, T., "Minimal Internet Key Exchange Version 2
              (IKEv2) Initiator Implementation", RFC 7815,
              DOI 10.17487/RFC7815, March 2016, <https://www.rfc-

   [RFC7925]  Tschofenig, H., Ed. and T. Fossati, "Transport Layer
              Security (TLS) / Datagram Transport Layer Security (DTLS)
              Profiles for the Internet of Things", RFC 7925,
              DOI 10.17487/RFC7925, July 2016, <https://www.rfc-

   [RFC8046]  Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility
              with the Host Identity Protocol", RFC 8046,
              DOI 10.17487/RFC8046, February 2017, <https://www.rfc-

   [RFC8105]  Mariager, P., Petersen, J., Ed., Shelby, Z., Van de Logt,
              M., and D. Barthel, "Transmission of IPv6 Packets over
              Digital Enhanced Cordless Telecommunications (DECT) Ultra
              Low Energy (ULE)", RFC 8105, DOI 10.17487/RFC8105, May
              2017, <>.

   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,

              "IRTF Thing-to-Thing (T2TRG) Research Group",
              Web, n.d..

              "The Internet of Things Is Wildly Insecure--And Often
              Unpatchable", Web
              the_internet_of_thin.html, n.d..

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Internet-Draft                IoT Security                September 2017

   [SEAL]     "Simple Encrypted Arithmetic Library - SEAL",
              Web, n.d..

   [shodan]   "Shodan", Web, n.d..

   [sigfox]   "Sigfox - The Global Communications Service Provider for
              the Internet of Things (IoT)",
              Web, n.d..

   [Thread]   "Thread Group", Web, n.d..

   [TR69]     "Too Many Cooks - Exploiting the Internet-of-TR-
              069-Things", Web
              _lior_oppenheim_-_shahar_tal, n.d..

   [WG-6lo]   "IETF IPv6 over Networks of Resource-constrained Nodes
              (6lo) Working Group",
              Web, n.d..

              "IETF IPv6 over Low power WPAN (6lowpan) Working Group",
              Web, n.d..

   [WG-ACE]   "IETF Authentication and Authorization for Constrained
              Environments (ACE) Working Group",
              Web, n.d..

   [WG-ACME]  "Automated Certificate Management Environment Working
              Group", Web,

   [WG-CoRE]  "IETF Constrained RESTful Environment (CoRE) Working
              Group", Web,

   [WG-FUD]   "IETF Firmware UpDate (fud)",
              Web, n.d..

   [WG-LWIG]  "IETF Light-Weight Implementation Guidance (LWIG) Working
              Group", Web,

   [WG-MSEC]  "IETF MSEC Working Group",
              Web, n.d..

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   [wink]     "Wink's Outage Shows Us How Frustrating Smart Homes Could

   [ZB]       "ZigBee Alliance", Web, February

              Ziegeldorf, J., Garcia-Morchon, O., and K. Wehrle,,
              "Privacy in the Internet of Things: Threats and
              Challenges", Security and Communication Networks - Special
              Issue on Security in a Completely Interconnected World ,

Authors' Addresses

   Oscar Garcia-Morchon
   Philips IP&S
   High Tech Campus 5
   Eindhoven, 5656 AA
   The Netherlands


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


   Mohit Sethi
   Hirsalantie 11
   Jorvas, 02420


Garcia-Morchon, et al.   Expires March 23, 2018                [Page 46]