Network Working Group O. Garcia-Morchon
Internet-Draft Philips IP&S
Intended status: Informational S. Kumar
Expires: December 21, 2017 Philips Research
M. Sethi
Ericsson
June 19, 2017
State-of-the-Art and Challenges for the Internet of Things Security
draft-irtf-t2trg-iot-seccons-04
Abstract
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 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 ensure roll out of secure IoT services.
This document is a product of the IRTF Thing-to-Thing Research Group
(T2TRG).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 21, 2017.
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Copyright Notice
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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 . . . . . . . . . . . . . . . . . 18
5. Challenges for a Secure IoT . . . . . . . . . . . . . . . . . 21
5.1. Constraints and Heterogeneous Communication . . . . . . . 21
5.1.1. Resource Constraints . . . . . . . . . . . . . . . . 22
5.1.2. Denial-of-Service Resistance . . . . . . . . . . . . 23
5.1.3. End-to-end security, protocol translation, and the
role of middleboxes . . . . . . . . . . . . . . . . . 23
5.1.4. New network architectures and paradigm . . . . . . . 25
5.2. Bootstrapping of a Security Domain . . . . . . . . . . . 26
5.3. Operational Challenges . . . . . . . . . . . . . . . . . 26
5.3.1. Group Membership and Security . . . . . . . . . . . . 26
5.3.2. Mobility and IP Network Dynamics . . . . . . . . . . 27
5.4. Software update . . . . . . . . . . . . . . . . . . . . . 28
5.5. Verifying device behavior . . . . . . . . . . . . . . . . 29
5.6. End-of-life . . . . . . . . . . . . . . . . . . . . . . . 29
5.7. Testing: bug hunting and vulnerabilities . . . . . . . . 30
5.8. Quantum-resistance . . . . . . . . . . . . . . . . . . . 30
5.9. Privacy protection . . . . . . . . . . . . . . . . . . . 31
5.10. Data leakage . . . . . . . . . . . . . . . . . . . . . . 32
5.11. Trustworthy IoT Operation . . . . . . . . . . . . . . . . 32
6. Conclusions and Next Steps . . . . . . . . . . . . . . . . . 33
7. Security Considerations . . . . . . . . . . . . . . . . . . . 33
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
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9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33
10. Informative References . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
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. Since then, the development of the underlying
concepts and technologies has increased the pace of its adoption. It
is not surprising that IoT has received significant attention from
the research community to (re)design, apply, and use of standard
Internet technology and protocols for the IoT.
The introduction of IPv6 and web services as fundamental building
blocks for IoT applications [RFC6568] promises to bring several
advantages including: (i) a homogeneous protocol ecosystem that
allows simple integration with 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 Internet Draft 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 conclusions.
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
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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.
We consider for example, 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, and
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
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, and 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 important.
The thing is later installed and commissioned within a network by an
installer during the bootstrapping phase. Specifically, the device
identity and the secret keys used during normal operation are
provided to the device during this phase. Different subcontractors
may install different IoT devices for different purposes.
Furthermore, the installation and bootstrapping procedures may not be
a 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. 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
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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 phase
until the device is decommissioned at the end of its lifecycle.
However, the end-of-life of a device does not necessarily mean that
it is defective 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
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
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(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 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 the IoT:
1. The 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 smart object: describes the way
security parameters, keys, processes, 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 pacemaker, may
rely on methods to protect cryptographic keys and functionality.
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
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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 TCP/IP stack. 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 communication pattern, 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 |<-+ :
: +-----------+: : +-----------+ : :+-----------+ :
:.......................: :...............: :.......................:
Overview of Security Mechanisms.
Figure 2
Inspired by the security framework for routing over low power and
lossy network [ID-Tsao], 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
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executes the bootstrapping protocol with the configuration entity,
thus obtaining the required device identities and the keying
material. The security service on a thing in turn stores the
received keying material for the network layer and application
security mechanisms for secure communication. Things can then
securely communicate with each other during their operational phase
by means of the employed network and application security mechanisms.
3. Security Threats and Managing Risk
This section explores security threats and vulnerabilities in the IoT
and discusses how to manage risks. Security threats have been
analyzed in related IP protocols 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 reserve 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
implemented within the cloned thing, such as a backdoor.
2. Malicious substitution of things: During the installation of a
thing, a genuine thing may be substituted with a similar variant
of lower quality without being detected. The main motivation may
be cost savings, where the installation of lower-quality things
(for example, non-certified products) may significantly reduce
the installation and operational costs. The installers can
subsequently resell the genuine things to gain further financial
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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 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 are 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 be able to differentiate friends and foes
via completely automated mechanisms. Thus, even if the key
establishment protocol provides cryptographic device
authentication, this knowledge on device identities may still
need complementing with a human-assisted authorization step
(thereby, presenting a weak link and offering the potential of
man-in-the-middle attacks this way).
5. Firmware Replacement attack: When a thing is in operation or
maintenance phase, its firmware or software may be updated to
allow for new functionality or new features. An attacker may be
able to exploit such a firmware upgrade by replacing the thing's
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
vulnerabilities that might be exploited by attackers.
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6. Extraction of private information: IoT devices (such as sensors,
actuators, etc.) are usually 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).
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 IoT since
an attacker might be located in the backend and target resource-
constrained devices that are part of a Low-power and Lossy
Network (LLN) [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.
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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 RFCs and ongoing
standardization efforts that include a threat model that might apply
to the IoT.
+------------------+------------------+------------------+
| Manufacturing | Installation/ | Operation |
| | Commissioning | |
+------------+------------------+------------------+------------------+
|System-level| Device Cloning |Substitution |Privacy threat |
| | |ACE-OAuth(draft) |Extraction of |
| | | |private inform. |
+------------+------------------+------------------+------------------+
|Application | |RFC2818, RFC7252 |RFC2818, Firmware |
|Layer | |OSCOAP(draft) |replacement |
+------------+------------------+------------------+------------------+
|Transport | | Eavesdropping & |Eavesdropping |
|Layer | | Man-in-the-middle|Man-in-the-middle |
+------------+------------------| attack, RFC7925 |------------------+
|Network | | RFC4919, RFC5713 |RFC4919,DoS attack|
|Layer | | RFC3833, RFC3756 |Routing attack |
| | | |RFC3833 |
+------------+------------------+------------------+------------------+
|Physical | | |DoS attack |
|Layer | | | |
+-------------------------------+------------------+------------------+
Figure 3: Classification of threats according to the lifecycle phases
and security building blocks.
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 the 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,
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 the IoT
system while considering their likelihood and impact. It also
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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 of 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 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 the IoT as proposed by other
bodies.
4.1. IP-based IoT Protocols and Standards
Nowadays, there exists a multitude of control protocols for the IoT.
For BAC systems, the ZigBee standard [ZB], BACNet [BACNET], or DALI
[DALI] play key roles. Recent trends, however, focus on an all-IP
approach for system control.
In this setting, a number of IETF working groups are designing new
protocols for resource-constrained networks of smart things. The
6LoWPAN working group [WG-6LoWPAN] for example has defined methods
and protocols for the efficient transmission and adaptation of IPv6
packets over IEEE 802.15.4 networks [RFC4944].
The CoRE working group [WG-CoRE] among other things 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 things.
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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] URIs.
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 is currently being written to define 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].
In addition to defining a routing protocol, the IETF has also
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 Cordless Telecommunications (DECT) Ultra
Low Energy (ULE) air interface [RFC8105], and Near Field
Communication (NFC) [ID-6lonfc].
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.
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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 extremely
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. There is
ongoing work to specify CBOR Object Signing and Encryption (COSE)
[ID-cose] that would provide services similar to JWS and JWT.
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,
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 would enable 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.
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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
protocol.
6. Fairhair Alliance [Fairhair]: Specifies a middle-ware for the IoT
based Building Automation and Lighting System that can
interoperate with different application standards for the
professional domain.
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
In the context of the IP-based IoT solutions, consideration of TCP/IP
security protocols is important. There are a wide range of
specialized as well as general-purpose key exchange and 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].
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 communications security for resource-
constrained nodes.
Migault et al. [ID-dietesp] are working on a compressed version of
IPsec so that it can easily be used by resource-constrained IoT
devices. They rely on the Internet Key Exchange Protocol version 2
(IKEv2) for negotiating the compression format.
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OSCOAP [ID-OSCOAP] is a proposal that protects CoAP messages by
wrapping them in the CBOR Object Signing and Encryption (COSE)
[ID-cose] format. Thus, OSCOAP falls in the category of object
security and it can be applied wherever CoAP can.
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]
that takes lossy low-power networks into account at the
authentication and key exchange level.
Transport Layer Security (TLS) and its datagram-oriented variant DTLS
secure transport-layer connections. TLS provides security for TCP
and requires a reliable transport, while DTLS secures and uses
datagram-oriented protocols such as UDP. Both protocols are
intentionally kept similar and share the same ideology and cipher
suites.
The Extensible Authentication Protocol (EAP) is an authentication
framework supporting multiple authentication methods. EAP runs
directly over the data link layer and, thus, does not require the
deployment of IP. It supports duplicate detection and
retransmission, but does not allow for packet fragmentation. The
Protocol for Carrying Authentication for Network Access (PANA) is a
network-layer transport for EAP that enables network access
authentication between clients and the network infrastructure. In
EAP terms, PANA is a UDP-based EAP lower layer that runs between the
EAP peer and the EAP authenticator.
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 ||<-+ :
: +===========+=====+===========+=====+===========+ :
:.......................: :...............: :.......................:
Relationships between IP-based security protocols.
Figure 4
4.3. IoT Security Guidelines
Recent large scale Denial of Service (DoS) attacks on the Internet
Infrastructure from compromised IoT devices has prompted many
different standards bodies and consortia to provide guidelines for
developers and the Internet community at large to build secure IoT
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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/IEEE 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
profiles.
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 device could use hardware-root of trust to ensure that
only authorized software runs on the device.
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
Internet draft 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
summarized.
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,
deployment of such insecure devices poses a severe threat. The vast
amount of devices and their inherent mobile nature also implies that
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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, it does not prevent
external (passive) attacks originating due to 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
[NIST-SP80053].
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 the IoT and
then discuss how existing Internet security protocols cope with these
technical and conceptual challenges through the lifecycle of a thing.
Figure 2 summarizes which requirements need to be met in the
lifecycle phases as well as some of the considered protocols. This
discussion should neither be understood as a comprehensive evaluation
of all protocols, nor can it cover all possible aspects of IoT
security. Yet, it aims at showing concrete limitations of existing
Internet security protocols in some areas rather than giving an
abstract discussion about general properties of the protocols. In
this regard, the discussion handles issues that are most important
from the authors' perspectives.
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 frequently constrained
nodes in terms of CPU, memory, and energy budget available. 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
of 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 ECC
[RFC5246], [RFC5903], [RFC7401], and [ID-HIP]. Moreover, all
protocols have been revised in the last years to enable crypto
agility, making cryptographic primitives interchangeable. However,
these improvements are only a first step in reducing the computation
and communication overhead of Internet protocols. The question
remains if other approaches can be applied to leverage key agreement
in these heavily resource-constrained environments.
A further fundamental need refers to the limited energy budget
available to IoT nodes. Careful protocol (re)design and usage is
required to reduce not only the energy consumption during normal
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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
middleboxes
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. For providing end-to-end
security services such as confidentiality and integrity protection on
packet data, message authentication codes or encryption is typically
used. These protection methods render the protected parts of the
packets immutable as rewriting is either not possible because a) the
relevant information is encrypted and inaccessible to the gateway or
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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 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 easily 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 in the 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
MAC 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 except those parts that the proxy
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 limited to be widely applicable.
5. Message authentication codes that sustain transformation can be
realized by considering the order of transformation and
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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 data prevents gateways from
transforming packets.
6. Object security based mechanisms 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) [ID-cose] (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
CoAP.
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 the 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 communicate directly amongst themselves with or
without support from the network. This communication paradigm is
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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 and in the 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
phase.
5.3.1. Group Membership and Security
Group key negotiation is an important security service for the T2Ts
and Ts2T communication patterns in the IoT. 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
of 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,
i.e., based on multicast IP. If the same security association is
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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 the 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 in live deployments for years and even
decades. Additionally, these devices typically operate unattended
with direct Internet connectivity. Therefore, a remote software
update mechanism to fix vulnerabilities, to update configuration
settings, and for adding new functionality is needed.
Schneier [SchneierSecurity] in his essay expresses concerns about the
status of software and firmware update mechanisms for Internet of
Things (IoT) devices. He highlights several challenges that hinder
mechanisms for secure software update of IoT devices. First, there
is a lack of incentives for manufactures, vendors and others on the
supply chain to issue updates for their devices. Second, parts of
the software running on the IoT devices is simply a binary blob
without any source code available. Since the complete source code 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
updates.
The FTC staff report on Internet of Things - Privacy & Security in a
Connected World [FTCreport] and the Article 29 Working Party Opinion
8/2014 on the on Recent Developments on the Internet of Things
[Article29] also document the challenges for secure remote software
update of IoT devices. They note that even providing such a software
update capability may add new vulnerabilities for constrained
devices. For example, a buffer overflow vulnerability in the
implementation of a software update protocol (TR69) [TR69] and an
expired certificate in a hub device [wink] demonstrate how the
software update process itself can introduce vulnerabilities.
While powerful IoT devices that run general purpose operating systems
can make use of sophisticated software update mechanisms known from
the desktop world, a more considerate effort is needed for resource-
constrained devices that don't have any operating system and are
typically not equipped with a memory management unit or similar
tools. The IAB also organized a workshop to understand the
challenges for secure software update of IoT devices. A summary of
the workshop and the proposed next steps have been documented
[iotsu].
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5.5. Verifying device behavior
Users often have a false sense of privacy when using new Internet of
Things (IoT) appliances such as Internet-connected smart televisions,
speakers and cameras. Recent revelations have shown that this user
belief is often unfounded. Many IoT device vendors have been caught
collecting sensitive private data through these connected appliances
with or without appropriate user warnings [cctv].
An IoT device user/owner would like to monitor and 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 the 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
question.
5.6. End-of-life
Like all commercial devices, most IoT devices will be end-of-lifed by
vendors or even network operators. 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 they
were end-of-lifed. Admittedly these are not easy for an average
users to install and configure on their devices. With the deployment
of millions of IoT devices, simpler mechanisms are needed to allow
users to add new root-of-trusts and install software and firmware
from other sources once the device has been end-of-lifed.
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5.7. Testing: bug hunting and vulnerabilities
Given that the 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 combination of devices of
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
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
algorithm.
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
available.
This situation would require us to move to quantum-resistant
alternatives, in particular, for those functionalities involving key
exchange, public-key encryption and signatures. While such future
planning is hard, it may be a necessity in certain critical IoT
deployments which are expected to last decades or more. Although
increasing the key-size of the different algorithms is definitely an
option, it would also incur additional computational overhead and
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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 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 the 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]:
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 him.
3. Profiling - is about creating a profile of the user and her
preferences.
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.
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5.10. Data leakage
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
more advance techniques that a traditional black box model does not
consider such as 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 perform attacks on devices
deployed in other locations.
2. source code that might let the user determine bugs or find
exploits to perform other types of attacks, or just sell it,
3. proprietary algorithms that could be counterfeited or modified to
perform advanced attacks.
Protection against such data leakage patterns is not trivial since
devices are inherently resource-constrained. An open question is
which techniques can be used to protect IoT 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 secure vulnerabilities. An example is 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, 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. 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]. The idea behind MUD files is
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simple: devices would disclose the location of its 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 rules.
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, security challenges, and state-of-the-art to
mitigate security threats.
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 the IoT should
be secured, there are many challenges ahead that require further
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,
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.
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10. Informative References
[Article29]
"Opinion 8/2014 on the on Recent Developments on the
Internet of Things", Web http://ec.europa.eu/justice/data-
protection/article-29/documentation/opinion-
recommendation/files/2014/wp223_en.pdf, n.d..
[AUTO-ID] "AUTO-ID LABS", Web http://www.autoidlabs.org/, September
2010.
[BACNET] "BACnet", Web http://www.bacnet.org/, February 2011.
[BITAG] "Internet of Things (IoT) Security and Privacy
Recommendations", Web http://www.bitag.org/report-
internet-of-things-security-privacy-recommendations.php,
n.d..
[cctv] "Backdoor In MVPower DVR Firmware Sends CCTV Stills To an
Email Address In China", Web
https://hardware.slashdot.org/story/16/02/17/0422259/
backdoor-in-mvpower-dvr-firmware-sends-cctv-stills-to-an-
email-address-in-china, n.d..
[CSA] "Security Guidance for Early Adopters of the Internet of
Things (IoT)", Web
https://downloads.cloudsecurityalliance.org/whitepapers/Se
curity_Guidance_for_Early_Adopters_of_the_Internet_of_Thin
gs.pdf, n.d..
[d2dsecurity]
Haus, M., Waqas, M., Ding, A., Li, Y., Tarkoma, S., and J.
Ott, "Security and Privacy in Device-to-Device (D2D)
Communication: A Review", Paper IEEE Communications
Surveys and Tutorials, 2016.
[DALI] "DALI", Web http://www.dalibydesign.us/dali.html, February
2011.
[DHS] "Strategic Principles For Securing the Internet of Things
(IoT)", Web
https://www.dhs.gov/sites/default/files/publications/
Strategic_Principles_for_Securing_the_Internet_of_Things-
2016-1115-FINAL....pdf, n.d..
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[ENISA_ICS]
"Communication network dependencies for ICS/SCADA
Systems", European Union Agency For Network And
Information Security , February 2017.
[ETSI_GR_QSC_001]
"Quantum-Safe Cryptography (QSC);Quantum-safe algorithmic
framework", European Telecommunications Standards
Institute (ETSI) , June 2016.
[Fairhair]
"Fairhair Alliance", Web https://www.fairhair-
alliance.org/, n.d..
[FCC] "Federal Communications Comssion Response 12-05-2016",
FCC , February 2016.
[FTCreport]
"FTC Report on Internet of Things Urges Companies to Adopt
Best Practices to Address Consumer Privacy and Security
Risks", Web https://www.ftc.gov/news-events/press-
releases/2015/01/ftc-report-internet-things-urges-
companies-adopt-best-practices, n.d..
[GSMAsecurity]
"GSMA IoT Security Guidelines", Web
http://www.gsma.com/connectedliving/future-iot-networks/
iot-security-guidelines/, n.d..
[ID-6lonfc]
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.
[ID-6tisch]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work
in progress), January 2017.
[ID-aceoauth]
Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
H. Tschofenig, "Authentication and Authorization for
Constrained Environments (ACE)", draft-ietf-ace-oauth-
authz-06 (work in progress), March 2017.
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[ID-bootstrap]
Sarikaya, B., Sethi, M., and A. Sangi, "Secure IoT
Bootstrapping: A Survey", draft-sarikaya-t2trg-
sbootstrapping-03 (work in progress), February 2017.
[ID-cose] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
draft-ietf-cose-msg-24 (work in progress), November 2016.
[ID-Daniel]
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.
[ID-dietesp]
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.
[ID-HIP] Moskowitz, R., "HIP Diet EXchange (DEX)", draft-moskowitz-
hip-rg-dex-06 (work in progress), May 2012.
[ID-Moore]
Moore, K., Barnes, R., and H. Tschofenig, "Best Current
Practices for Securing Internet of Things (IoT) Devices",
draft-moore-iot-security-bcp-00 (work in progress),
October 2016.
[ID-MUD] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
Description Specification", draft-ietf-opsawg-mud-06 (work
in progress), May 2017.
[ID-Nikander]
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.
[ID-OSCOAP]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security of CoAP (OSCOAP)", draft-selander-ace-
object-security-06 (work in progress), October 2016.
[ID-rd] Shelby, Z., Koster, M., Bormann, C., and P. Stok, "CoRE
Resource Directory", draft-ietf-core-resource-directory-10
(work in progress), March 2017.
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[ID-senml]
Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
Bormann, "Media Types for Sensor Measurement Lists
(SenML)", draft-ietf-core-senml-08 (work in progress), May
2017.
[ID-Tsao] Tsao, T., Alexander, R., Dohler, M., Daza, V., and A.
Lozano, "A Security Framework for Routing over Low Power
and Lossy Networks", draft-ietf-roll-security-framework-07
(work in progress), January 2012.
[ID-Williams]
Williams, M. and J. Barrett, "Mobile DTLS", draft-barrett-
mobile-dtls-00 (work in progress), March 2009.
[IEEE802ah]
"Status of Project IEEE 802.11ah, IEEE P802.11- Task Group
AH-Meeting Update.",
Web http://www.ieee802.org/11/Reports/tgah_update.htm,
n.d..
[IIoT] "Industrial Internet Consortium",
Web http://www.iiconsortium.org/, n.d..
[IoTSecFoundation]
"Establishing Principles for Internet of Things Security",
Web https://iotsecurityfoundation.org/establishing-
principles-for-internet-of-things-security/, n.d..
[iotsu] "Patching the Internet of Things: IoT Software Update
Workshop 2016", Web
https://www.ietf.org/blog/2016/07/patching-the-internet-
of-things-iot-software-update-workshop-2016/, n.d..
[IPSO] "IPSO Alliance", Web http://www.ipso-alliance.org, n.d..
[lora] "LoRa - Wide Area Networks for IoT", Web https://www.lora-
alliance.org/, n.d..
[LWM2M] "OMA LWM2M", Web http://openmobilealliance.org/iot/
lightweight-m2m-lwm2m, n.d..
[nbiot] "NarrowBand IoT", Web
http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_69/Docs/
RP-151621.zip, n.d..
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[NHTSA] "Cybersecurity Best Practices for Modern Vehicles", Web
https://www.nhtsa.gov/staticfiles/nvs/
pdf/812333_CybersecurityForModernVehicles.pdf, n.d..
[NIST-Guide]
Ross, R., McEvilley, M., and J. Oren, "Systems Security
Engineering", Web
http://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-160.pdf, n.d..
[NIST-SP80053]
"Security and Privacy Controls for Federal Information
Systems and Organizations",
Web http://dx.doi.org/10.6028/NIST.SP.800-53r4, n.d..
[nist_lightweight_project]
"NIST lightweight Project", Web www.nist.gov/programs-
projects/lightweight-cryptography,
www.nist.gov/sites/default/files/documents/2016/10/17/
sonmez-turan-presentation-lwc2016.pdf, n.d..
[OCF] "Open Connectivity Foundation",
Web https://openconnectivity.org/, n.d..
[OneM2M] "OneM2M", Web http://www.onem2m.org/, n.d..
[OWASP] "IoT Security Guidance",
Web https://www.owasp.org/index.php/IoT_Security_Guidance,
n.d..
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<http://www.rfc-editor.org/info/rfc3748>.
[RFC3756] Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
Neighbor Discovery (ND) Trust Models and Threats",
RFC 3756, DOI 10.17487/RFC3756, May 2004,
<http://www.rfc-editor.org/info/rfc3756>.
[RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain
Name System (DNS)", RFC 3833, DOI 10.17487/RFC3833, August
2004, <http://www.rfc-editor.org/info/rfc3833>.
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[RFC4016] Parthasarathy, M., "Protocol for Carrying Authentication
and Network Access (PANA) Threat Analysis and Security
Requirements", RFC 4016, DOI 10.17487/RFC4016, March 2005,
<http://www.rfc-editor.org/info/rfc4016>.
[RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol
(MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,
<http://www.rfc-editor.org/info/rfc4555>.
[RFC4621] Kivinen, T. and H. Tschofenig, "Design of the IKEv2
Mobility and Multihoming (MOBIKE) Protocol", RFC 4621,
DOI 10.17487/RFC4621, August 2006,
<http://www.rfc-editor.org/info/rfc4621>.
[RFC4738] Ignjatic, D., Dondeti, L., Audet, F., and P. Lin, "MIKEY-
RSA-R: An Additional Mode of Key Distribution in
Multimedia Internet KEYing (MIKEY)", RFC 4738,
DOI 10.17487/RFC4738, November 2006,
<http://www.rfc-editor.org/info/rfc4738>.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, DOI 10.17487/RFC4919, August 2007,
<http://www.rfc-editor.org/info/rfc4919>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.
[RFC5191] Forsberg, D., Ohba, Y., Ed., Patil, B., Tschofenig, H.,
and A. Yegin, "Protocol for Carrying Authentication for
Network Access (PANA)", RFC 5191, DOI 10.17487/RFC5191,
May 2008, <http://www.rfc-editor.org/info/rfc5191>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>.
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[RFC5713] Moustafa, H., Tschofenig, H., and S. De Cnodder, "Security
Threats and Security Requirements for the Access Node
Control Protocol (ANCP)", RFC 5713, DOI 10.17487/RFC5713,
January 2010, <http://www.rfc-editor.org/info/rfc5713>.
[RFC5903] Fu, D. and J. Solinas, "Elliptic Curve Groups modulo a
Prime (ECP Groups) for IKE and IKEv2", RFC 5903,
DOI 10.17487/RFC5903, June 2010,
<http://www.rfc-editor.org/info/rfc5903>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[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,
<http://www.rfc-editor.org/info/rfc6550>.
[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,
<http://www.rfc-editor.org/info/rfc6551>.
[RFC6568] Kim, E., Kaspar, D., and JP. Vasseur, "Design and
Application Spaces for IPv6 over Low-Power Wireless
Personal Area Networks (6LoWPANs)", RFC 6568,
DOI 10.17487/RFC6568, April 2012,
<http://www.rfc-editor.org/info/rfc6568>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<http://www.rfc-editor.org/info/rfc6690>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
[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,
<http://www.rfc-editor.org/info/rfc6973>.
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[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <http://www.rfc-editor.org/info/rfc7049>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<http://www.rfc-editor.org/info/rfc7252>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<http://www.rfc-editor.org/info/rfc7401>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>.
[RFC7520] Miller, M., "Examples of Protecting Content Using JSON
Object Signing and Encryption (JOSE)", RFC 7520,
DOI 10.17487/RFC7520, May 2015,
<http://www.rfc-editor.org/info/rfc7520>.
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[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,
<http://www.rfc-editor.org/info/rfc7668>.
[RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
<http://www.rfc-editor.org/info/rfc7696>.
[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2
(IKEv2) Initiator Implementation", RFC 7815,
DOI 10.17487/RFC7815, March 2016,
<http://www.rfc-editor.org/info/rfc7815>.
[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,
<http://www.rfc-editor.org/info/rfc7925>.
[RFC8046] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility
with the Host Identity Protocol", RFC 8046,
DOI 10.17487/RFC8046, February 2017,
<http://www.rfc-editor.org/info/rfc8046>.
[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, <http://www.rfc-editor.org/info/rfc8105>.
[RG-T2TRG]
"IRTF Thing-to-Thing (T2TRG) Research Group",
Web https://datatracker.ietf.org/rg/t2trg/charter/,
December 2015.
[SchneierSecurity]
"The Internet of Things Is Wildly Insecure--And Often
Unpatchable", Web
https://www.schneier.com/essays/archives/2014/01/
the_internet_of_thin.html, n.d..
[SEAL] "Simple Encrypted Arithmetic Library - SEAL",
Web https://sealcrypto.codeplex.com/, n.d..
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[sigfox] "Sigfox - The Global Communications Service Provider for
the Internet of Things (IoT)",
Web https://www.sigfox.com/, n.d..
[Thread] "Thread Group", Web http://threadgroup.org/, n.d..
[TR69] "Too Many Cooks - Exploiting the Internet-of-TR-
069-Things", Web https://media.ccc.de/v/31c3_-_6166_-_en_-
_saal_6_-_201412282145_-_too_many_cooks_-
_exploiting_the_internet-of-tr-069-things_-
_lior_oppenheim_-_shahar_tal, n.d..
[WG-6LoWPAN]
"IETF 6Lo Working Group",
Web http://tools.ietf.org/wg/6lowpan/, February 2011.
[WG-ACE] "IETF Authentication and Authorization for Constrained
Environments (ACE) Working Group",
Web https://datatracker.ietf.org/wg/ace/charter/, June
2014.
[WG-CoRE] "IETF Constrained RESTful Environment (CoRE) Working
Group", Web https://datatracker.ietf.org/wg/core/charter/,
February 2011.
[WG-LWIG] "IETF Light-Weight Implementation Guidance (LWIG) Working
Group", Web https://datatracker.ietf.org/wg/lwig/charter/,
March 2011.
[WG-MSEC] "MSEC Working Group",
Web http://datatracker.ietf.org/wg/msec/, n.d..
[wink] "Wink's Outage Shows Us How Frustrating Smart Homes Could
Be",
Web http://www.wired.com/2015/04/smart-home-headaches/,
n.d..
[ZB] "ZigBee Alliance", Web http://www.zigbee.org/, February
2011.
[Ziegeldorf]
Ziegeldorf, J., Garcia-Morchon, O., and K. Wehrle,,
"Privacy in the Internet of Things: Threats and
Challenges", Paper Security and Communication Networks -
Special Issue on Security in a Completely Interconnected
World, 2013.
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Authors' Addresses
Oscar Garcia-Morchon
Philips IP&S
High Tech Campus 5
Eindhoven, 5656 AA
The Netherlands
Email: oscar.garcia-morchon@philips.com
Sandeep S. Kumar
Philips Research
High Tech Campus
Eindhoven, 5656 AA
The Netherlands
Email: sandeep.kumar@philips.com
Mohit Sethi
Ericsson
Hirsalantie 11
Jorvas
Finland
Email: mohit@piuha.net
Garcia-Morchon, et al. Expires December 21, 2017 [Page 44]
