Embedded Systems Security Challenges

Konstantinos Fysarakis

, George Hatzivasilis

, Konstantinos Rantos

Alexandros Papanikolaou

and Charalampos Manifavas

Dept. of Electronic & Computer Engineering, Technical University of Crete, Chania, Greece

Dept. of Computer & Informatics Engineering, Eastern Macedonia and Thrace Institute of Technology, Kavala, Greece

Dept. of Informatics Engineering, Technological Educational Institute of Crete, Heraklion, Crete, Greece

Keywords:

Embedded Devices, Security, Denial of Service, Lightweight Cryptography, Location Privacy, Secure Routing.

Abstract:

In a world of pervasive computing, embedded systems can be found in a wide range of products and are em-

ployed in various heterogeneous domains. The abovementioned devices often need to access, store, manipulate

and/or communicate sensitive or even critical information, making the security of their resources and services

an important concern in their design process. These issues are further exacerbated by the resource-constrained

nature of the devices, in conjunction with the ever-present need for smaller size and lower production costs.

This paper aims to provide an overview of the challenges in designing secure embedded systems, covering

both node hardware and software issues, as well as relevant network protocols and cryptographic algorithms.

Moreover, recent advances in the ﬁeld are identiﬁed, highlighting opportunities for future research.

1 INTRODUCTION

Embedded systems (ESs) permeate our lives in vari-

ous forms, ranging from avionics to e-textiles, auto-

mobiles, home automation and wireless sensor nodes.

In terms of their physical size, they range from minia-

ture wearable or sensor nodes (i.e. motes) to large

industrial deployments of programmable logic con-

trollers (PLCs).

The various intrinsic and application-speciﬁc

characteristics of ESs complicate the task of guaran-

teeing the security, namely handling the conﬁdential-

ity, integrity and availability aspects of their applica-

tions and the data they handle. Their characteristics

habitually include resource constraints (namely com-

putational capabilities, storage capacity, memory and

power), dynamically formulated, remotely-managed

networking and even unattended operation in hostile

environment and time-critical applications. There-

fore, while securing networked computer systems is

not a novel concern, the techniques developed for per-

sonal and enterprise systems are often unsatisfactory

or even inapplicable to embedded devices.

In addition to the above, ES applications often fea-

ture direct interaction with the physical world, be-

ing responsible for vital, time-critical applications,

where a delay or a speed-up of even a fraction of a

second in system’s response or reaction could have

dire consequences. This further differentiates ES se-

curity, as a security incident in a critical application

may lead to asset damage or even personal injury

and death. Researchers recently demonstrated that

it is feasible to manipulate all critical sub-systems

in modern automobiles by using a wireless-enabled

MP3 player connected to the vehicle’s embedded con-

trol network (Koscher et al., 2010). The presented

attacks include accessing the brake controller, thus

disabling or forcibly activating the brakes and con-

sequently compromising the safety of the driver and

passengers, as well as injecting malicious code to

erase any evidence of tampering after a crash.

Moreover, next-generation ES services, like the

ones pertaining to the Internet of Things (IoT), may

require the integration of multiple administrative do-

mains (e.g. one domain may host the devices and en-

able access to devices and information,whereas an-

other domain may make use of the information for

designing innovative services). Each domain will typ-

ically have its own security requirements and con-

straints, therefore ensuring interoperability of security

is a challenging task (Alam et al., 2011).

The paper is organised as follows: Section 2

presents some physical security issues that are evi-

dent in embedded systems. The various access control

mechanisms used for controlling access to resources

are presented in Sec. 3. Indicative examples of crypto-

255

Fysarakis K., Hatzivasilis G., Rantos K., Papanikolaou A. and Manifavas C..

Embedded Systems Security Challenges.

DOI: 10.5220/0004901602550266

In Proceedings of the 4th International Conference on Pervasive and Embedded Computing and Communication Systems (MeSeCCS-2014), pages

255-266

ISBN: 978-989-758-000-0

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

graphic mechanisms specially-crafted for embedded

systems are presented in Sec. 4. Various protocol and

management issues are presented in Sec. 5, and the

paper concludes in Sec. 6.

2 PHYSICAL SECURITY ISSUES

Regarding the physical layer and given the often unat-

tended nature of deployed ESs, sometimes within

hostile environments, the risk of device tampering

should not be ignored. In the remainder of this sec-

tion, some aspects of physical security in ESs are pre-

sented.

2.1 Side Channel Attacks

A malicious entity’s physical access to a non-tamper-

resistant device, apart from providing physical ac-

cess to the system components, would also enable

the launch of various attacks like micro-probing and

reverse engineering or sophisticated side-channel at-

tacks (SCA), timing attacks, simple power analy-

sis (SPA), differential power analysis (DPA), as well

as their electro-magnetic counterparts, SEMA and

DEMA respectively, and also differential fault attacks

(DFA). The aforementioned methods can potentially

expose critical information concerning the operation

of the device (algorithms used, length of keys etc.)

which could prove critical to the security both of the

device itself and the network as a whole.

In the case of ESs utilising ﬁeld-programmable

gate arrays (FPGAs), the concept of run-time re-

conﬁguration (Dan

ek et al., 2008) can be explored

to reduce component count and/or power consump-

tion, increase fault tolerance etc. as needed. Self-

reconﬁgurability can, for example, make a node more

secure against side-channel attacks through the mea-

surement of electromagnetic radiation and also im-

plement self-healing properties. Self-recovery mech-

anisms could reallocate functional blocks to mark

and replace faulty resources, through device repro-

gramming in the case of self-reconﬁgurable nodes or

through controlled degradation of service techniques

in less “intelligent” devices.

2.2 Trusted Platform Module

A Trusted Platform Module – TPM (Trusted Plat-

form Module, 2009), is a microcontroller that can se-

curely store a relatively small amount of information

on it, which can then be used either for authenticat-

ing the platform (e.g. passwords, certiﬁcates, encryp-

tion keys) or for ensuring that the platform has not

been breached (e.g. platform measurements, conﬁgu-

ration data). It is worth clarifying that the microcon-

troller does not control the software that is running

on the platform itself. Instead, through the tamper-

resistant security functions it provides, the platform’s

operating system or any running applications access

the necessary information, so as to determine and im-

plement their security policies accordingly. The soft-

ware embedded on such a TPM component is directly

related to the component’s physical size (the higher

the memory requirements, the larger the module’s sur-

face) and consequently cost. Any optimisation of the

module’s software will have a direct impact on the

overall execution speed, as well as to the power con-

sumption (faster execution allows the module to re-

turn to a more power-sparring idle/sleep state).

2.3 Protection of Power Supply

Several types of embedded systems devices are

mostly battery-powered, something that creates issues

of energy constraints. Especially in cases where e.g.

small sensor nodes are meant to be used in unattended

environments, they are expected to operate for cer-

tain time intervals (sometimes spanning over a few

months) until they have their power source replaced

or recharged. An attacker could therefore launch a

Denial-of-Service (DoS) attack, aiming at draining

the battery power by forcing extensive use of the de-

vice’s wireless connection or CPU.

In order for the electronic parts of the embed-

ded device to function properly, continuous power is

required, with both voltage and current levels lying

within speciﬁc limits. The power source should also

be able to monitor its own state and react accordingly

in cases where an issue is detected that could affect

the normal operation of the system. Moreover, suit-

able fail-safe mechanisms should exist, implemented

in software and/or hardware, that would protect the

device and prevent any potential damage from spread-

ing across the rest of its components.

Most of the requirements mentioned above are sat-

isﬁed in modern uninterruptible power supply (UPS)

systems, nevertheless, they cannot easily be applied

to the operating environments of some embedded sys-

tems, due to strict size and cost constraints. Instead,

alternative solutions are implemented, such as energy

scavenging, super-capacitors, micro-solar cells and

remote/wireless power transferring schemes (Kurs

et al., 2007; Karalis et al., 2008), to name a few. Still,

such solutions must carefully be adopted to each spe-

ciﬁc scenario (e.g. a micro-solar cell is useless if the

device cannot be reached by enough direct sunlight),

also taking into consideration fail-safe options with

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

256

respect to the criticality of the possible failures and

the probability for them to occur, so as to protect the

device effectively.

3 ACCESS CONTROL

Access control mechanisms are essential to pre-

vent unauthorised/malicious entities to access the re-

sources, physical or otherwise, available to the ESs as

well as the hosting devices. The way access control is

implemented varies depending on the hardware capa-

bilities of the nodes, the type of network and the appli-

cation under consideration. Some common methods

include:

1. Proﬁle authentication: If a node has some speciﬁc

characteristics (e.g. hardware speciﬁcations, oper-

ating system), it can join an existing network.

2. Access code: Demonstrating knowledge of the

code grants access to the network and its re-

sources. This code can either be programmable

or conﬁgurable. This category includes typical

password access, based on memory data, switch

conﬁguration or any other procedure.

3. Predeﬁned topology: Only pre-established nodes

can join the network (e.g. MAC ﬁltering).

There is ongoing research on ES-speciﬁc access

control protocols since the commonly-used authen-

tication schemes, typically password-based, can be

impractical or even insecure when considering the

heterogeneous nature of ES networks can demon-

strate and the scalable remote manageability often re-

quired (Naedele, 2006). Moreover, even in wired em-

bedded networks and in industries such as automo-

tive and aviation, most control networks utilised (e.g.

Controller Area Network, Time-Triggered Protocol,

FlexRay) are designed with safety and reliability in

mind and do not feature any built-in security mech-

anisms like node authentication, data encryption or

prevention of DoS attacks (Szilagyi and Koopman,

2009; Szilagyi and Koopman, 2010), leading to crit-

ical vulnerabilities like the ones already mentioned

in (Koscher et al., 2010).

3.1 Policy-Based Access Control

ESs are often deployed in applications bound by strict

security requirements (e.g. e-Health applications are

a prime example), including secure transmission of

sensitive data to remote entities, instructions that need

to reach actuators in an unaltered form, robust entity

authentication and access control mechanisms (Al-

haqbani and Fidge, 2008).

Regarding the latter, among the proposed schemes

that have gained popularity are those where deci-

sions are made based on policy restrictions. Such a

scheme is the standardised by OASIS eXtensible Ac-

cess Control Markup Language (XACML), an XML-

based general-purpose policy decision language. Be-

sides being used for representing authorisation and

entitlement policies for managing access to resources,

it provides a processing model for evaluating requests

and making decisions based on the deﬁned set of poli-

cies (Rantos et al., 2012). Policy-based access control

allows dynamic decision making on controlled nodes’

resources based on policy restrictions set by the sys-

tem owner.

An XACML architecture commonly consists of

the following components:

• Policy Enforcement Point (PEP): The system en-

tity that performs access control, by making de-

cision requests and enforcing authorisation deci-

sions.

• Policy Administration Point (PAP): The system

entity that creates a policy or policy set.

• Policy Decision Point (PDP): The system entity

that evaluates applicable policy and renders an au-

thorisation decision.

• Policy Information Point (PIP): The system entity

that acts as a source of attribute values.

• Context Handler: It orchestrates the communica-

tions among the stakeholders, converts, if neces-

sary messages between their native forms and the

XACML canonical form, and collects all neces-

sary information for the PDP.

The aforementioned components are complemented

by a well-deﬁned set of policies which deﬁne the rules

that should be taken into account when examining ac-

cess requests.

In a typical data ﬂow model, authorisation re-

quests for accessing nodes’ resources, i.e. PEPs are

forwarded to PDPs together with the required at-

tributes taken from the PIP. The PDP evaluates the

request against the policy restrictions taken from PAP

and issues an authorisation decision which the PEP

has to enforce.

These components do not necessarily run on the

same node, mainly because resource-restricted nodes

do not have the capacity to accommodate them. In

this case more distributed approaches have to be

adopted to ofﬂoad computationally expensive opera-

tions run by a PDP to more powerful devices.

Still, unprotected policy messages would expose

the system’s security, revealing private information to

attackers who might also try to identify policy restric-

tions and do a mapping of the security measures taken

EmbeddedSystemsSecurityChallenges

257

for the speciﬁc environments, hence exploiting poten-

tial vulnerabilities. Moreover, in a more active ap-

proach, an attacker might masquerade as a legitimate

entity or modify policy-related messages, such as au-

thorisation requests and/or decisions, obligations or

advices in an attempt to downgrade adopted measures

and bypass access controls. To avoid the aforemen-

tioned problems, appropriate security measures, like

the ones detailed in later sections of this paper, have

to be deployed to safeguard message conﬁdentiality,

integrity and authentication.

3.2 Denial of Service (DoS)

The aim of a DoS or a Distributed DoS (DDoS) at-

tack is to harm the availability of a speciﬁc node or a

network of nodes, thus preventing or delaying legiti-

mate entities from accessing the services or resources

they wish to (Carl et al., 2006). DoS attacks on ES

nodes can take multiple forms, such as exploiting the

vulnerabilities in their software/ﬁrmware, or attack-

ing the network they belong to by jamming, misrout-

ing, ﬂooding and so on. DoS attacks can be mounted

more or less on every layer, by exploiting the par-

ticular characteristics or mechanisms found in them.

Their aim is to cause the nodes to constantly process

or send dummy data, thus draining their power source

via unnecessary use of their wireless connection and

prolonged demand for memory and CPU cycles. The

effects of such attacks are particularly critical in the

case of nano and micro/personal nodes, where the

power reserve is usually rather limited. In addition,

ﬂooding types of DoS attacks consume part of the net-

work’s bandwidth, which may also indirectly affect

the normal operation of the network or a signiﬁcant

part of it, depending on the overall network’s capac-

ity.

Another type of DoS attack involves the case

where an attacker gains physical access to the device

and modiﬁes or destroys it as a physical entity. De-

pending on the role of this particular node for the rest

of the network or cluster of nodes it belongs to, its un-

availability could have a signiﬁcant impact on these

entities. For instance, it could lead to partial or total

loss of the data sink, selection of non-optimal routes,

or even the loss of a control node that is vital for the

normal operation of the system.

Given that large-scale networks are most proba-

bly heterogeneous in their nature, they contain differ-

ent capabilities and vulnerabilities, which need to be

addressed independently for achieving effective pro-

tection against DoS attacks. What is more, in cases

where there is provision for dynamic network size

variation, shielding against DoS attacks can become a

very challenging task (Raymond and Midkiff, 2008).

In addition, the problem becomes even more complex

and difﬁcult to solve for cases where the available re-

sources and capabilities exhibit strict limitations.

In cases where the ES network is of an unat-

tended nature, the use of a remote management sys-

tem is vital. Nevertheless, such systems offer ad-

ditional attack surface and their compromise can al-

low an adversary to upload malicious ﬁrmware. In

this way, the attacker is able to corrupt memory and

data sent/received or even lead to permanent damage

of hardware sub-components by intended misconﬁg-

uration (Permanent DoS – PDoS, or bricking). The

success of such attacks is based on the fact that the

various ﬁrmware upgrade mechanisms are usually in-

secure and do not employ complex security mecha-

nisms for verifying authenticity and integrity, such as

the ones used in digital certiﬁcates. This process of

rendering a device unbootable or non-reﬂashable is

also known as phlashing (Smith, 2008).

One of the main reasons for the DoS attacks be-

ing relatively easy to successfully launch is the use of

old protocols that suffer from lack of security require-

ments. For instance, the IP protocol takes for granted

various assumptions regarding the trust of network

nodes and consequently does not dispute the related

information found in the packet headers and/or pay-

load. Any integrity-checking mechanisms are rather

primitive and simple in nature (e.g. checksums), as

their aim is to detect accidental data corruption and

not deliberate modiﬁcation of information. Therefore,

continuing to use such protocols as the base for build-

ing custom network communication protocols on it

makes it particularly hard to design (D)DoS-resilient

systems and services. An additional obstacle is the

fact that basic software methodologies do not take

into consideration security requirements, able to deal

with such kinds of attacks (Stefanidis and Serpanos,

2008).

The majority of the aforementioned attacks can

be avoided by employing suitable authentication, ac-

cess control and integrity-checking mechanisms. It is

also equally important to provide secure mechanisms

for node ﬁrmware deployment and software updates,

able to verify both the authenticity and integrity of

the ﬁrmware/software to be uploaded and reject it if it

does not pass the required checks. Furthermore, more

recent network protocols should be used, able to pro-

vide means and metrics for quantifying (D)DoS attack

resilience (Aad et al., 2008). The use of intrinsically

secure ES ﬁrmware offering various fail-safe mech-

anisms or even hardware redundancy could be em-

ployed in cases where dependability is highly critical

(e.g. avionics and the military), as they are expected

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

258

to increase the cost of the end-product.

4 CRYPTOGRAPHIC MECHANISMS

As has already been mentioned, embedded devices

often have inherent limitations in terms of process-

ing power, memory, storage and energy. Efﬁcient

algorithm designs and implementations that adhere

to these constraints, while satisfying application de-

mands, can signiﬁcantly impact battery lifetime and

allow the implementation of many applications.

Key management is an equally important issue,

both from a security and a management point of view.

The rather simple pre-shared key (PSK) scheme,

where every embedded device has the necessary cryp-

tographic keys pre-installed, is difﬁcult to manage in

distributed and dynamic environments (physical ac-

cess to the device is required) or in cases where there

is a large number of such devices. Moreover, the dis-

closure of the master key leads to the instant compro-

mise of all the system/network. Having an appropri-

ate scheme that triggers periodic re-keying limits the

amount of ciphertext that has been encrypted with the

same key, thus increasing the system’s security level.

This section presents several lightweight crypto-

graphic and key management schemes, suitable for

resource-constrained devices.

4.1 Lightweight Cryptography

Lightweight Cryptography (LWC) refers to algorith-

mic designs and implementations best suited for de-

ployment in such devices (e.g. RFIDs, sensor nodes,

contactless smartcards, mobile devices). There has al-

ready been signiﬁcant effort on the subject of crypto

optimisation, aiming to maintain the security level

that “traditional” algorithms and implementations of-

fer while narrowing what is often referred to as “bat-

tery gap” (Doomun and Soyjaudah, 2009), i.e. the

very high energy consumption overheads for support-

ing security on battery-constrained systems. A num-

ber of surveys (Preneel, 2009; Eisenbarth et al., 2007)

provide an overview of this subject.

ISO/IEC 29192 includes ciphers and crypto-

graphic mechanisms for LWC. The standards are

PRESENT (Bogdanov et al., 2007) and CLEFIA (Ak-

ishita and Hiwatari, 2012) for block ciphers, and

TRIVIUM (ECRYPT, 2008) and Enocoro (Watanabe

et al., 2008) for stream ciphers.

Compact implementations of “traditional” ci-

phers, like AES (Feldhofer et al., 2005), are also

applied to embedded devices. Newer lightweight

block ciphers are Humminbird-2 (Engels et al., 2011),

Piccolo (Shibutani et al., 2011), Simon (Beaulieu

et al., 2013), SPECK (Beaulieu et al., 2013),

ITUbee (Karakoc¸ et al., 2013). For stream ciphers,

the ﬁnalists of the eSTREAM project Grain, Salsa20,

Rabbit and HC128 (ECRYPT, 2008) are suitable for

LWC.

Hash functions design is another area where fur-

ther research is required. For LWC, compact im-

plementations of the standardised functions SHA-

2 (Bogdanov et al., 2008), SHA-3 (Gaj et al., 2012)

are examined. Newer functions that are suitable in

this domain are Blake (Gaj et al., 2012), Photon (Guo

et al., 2011), SPONGENT (Bogdanov et al., 2011)

and other hash functions based on lightweight block

ciphers, like DM-PRESENT (Bogdanov et al., 2008).

Asymmetric algorithms and protocols must also

be adapted to operate on devices with the afore-

mentioned resource limitations. This is an elaborate

task, since asymmetric ciphers are computationally

far more demanding than their symmetric counter-

parts and are usually executed on powerful hardware.

The performance gap is exacerbated on constrained

devices, such as 8-bit microcontrollers. Even an opti-

mised asymmetric algorithm (e.g. elliptic-curve cryp-

tography – ECC), performs 100 to 1000 times more

slowly than a standard symmetric algorithm (e.g.

AES), which correlates to a proportionally higher

power consumption.

In terms of practical relevance, two families of es-

tablished public-key algorithms stand out: ECC and

NTRU (Kamal and Youssef, 2009). ECC in partic-

ular is considered the most attractive option in ESs,

due to its small operand length and its relatively low

processing requirements. NTRU is the most popular

lattice-based cryptosystem. Its security is based on

the shortest vector problem and it can efﬁciently be

deployed on embedded systems. Compared to ECC

in hardware, NTRU is 1.5 times faster with only the

1/7 of the memory footprint. Compared to RSA in

software, it is 200 times faster in key generation, al-

most 3 times faster in encryption and 30 times faster

in decryption.

The need for lightweight cryptography introduces

major multi-dimensional challenges in cryptographic

algorithms design, from the ES operating system (OS)

to the hardware and software cryptographic provi-

sions embedded on the device itself. Hardware and

software co-design seems to offer the best results in

terms of speed/size ratio for many ubiquitous comput-

ing applications (Eisenbarth et al., 2007). Regarding

primitives that cannot yet be effectively implemented

(e.g. hashes in the case of crypto and public key

crypto in the case of asymmetric), alternatives could

be investigated so that the protocols which are based

EmbeddedSystemsSecurityChallenges

259

upon them can be researched further and perhaps put

into practice. Special care should be taken during

the development of optimised implementations so that

they do not introduce new leakage channels which

could be exploited by Side-Channel Attacks (SCA).

A comparative analysis of lightweight ciphers on

embedded systems was performed recently, where the

authors evaluate the proposed schemes based on per-

formance metrics and classify them for various types

of embedded devices (Manifavas et al., 2013). Vari-

ous cryptographic libraries exist that offer key estab-

lishment mechanisms and communication protocols,

like for example ULCL (Hatzivasilis et al., 2014),

CyaSSL and OpenSSL.

4.2 Key Distribution Mechanisms

Key distribution, either for initialisation (Kuo et al.,

2007) or re-keying has been a challenging topic es-

pecially for dynamic, heterogeneous and resource-

limited environments. The majority of these schemes

is based on symmetric mechanisms, thus requiring

pre-distribution of the shared secret with all the dis-

advantages already discussed. Other schemes (Doyle

et al., 2006) are being proposed as well, some

of which feature location-aware and identity-based

mechanisms. Although some of the proposed

schemes are indeed energy efﬁcient (Huang et al.,

2005a), key management based on shared secrets

has proven ineffective, especially in dynamically-

formulated infrastructures. There have been attempts

to correlate key establishment techniques to applica-

tions but these were based solely on the use of sym-

metric keys and on a framework level (Martin and Pa-

terson, 2008).

This has led part of the research community to fo-

cus its attention on public-key schemes (e.g. ECC).

This enables the distribution of authentic public keys

via insecure channels, as the verifying party does not

need to have a copy of the secret key. Therefore, a

mobile node’s key database may, for example, be up-

dated with all valid public keys once, according to a

pre-deﬁned schedule or ad hoc, and from that point

onwards the device will be able to authenticate other

entities in off-line mode.

Identity-based cryptography – IBC (Boneh and

Franklin, 2003) provides an alternative solution to

the very expensive, for many nodes, public-key cryp-

tography. IBC allows publicly-available information

that can uniquely identify participating nodes to be

utilised for the secure exchange of keys. Thus, nodes

do not have to depend on a public key infrastruc-

ture and digital certiﬁcates for the exchange of au-

thenticated public keys. The advent of identity-based

schemes and pairing-based cryptography has shown

that such schemes offer a promising solution for man-

aging keys in resource-constrained nodes (Oliveira

et al., 2011).

Even with a public-key scheme, we still need to

implement symmetric cryptography. Thus, alternative

schemes that are based only in symmetric cryptogra-

phy are also proposed (Chen and Chao, 2011; Simpli-

cio et al., 2010). Some of them are location-aware and

identity-based mechanisms and are energy-efﬁcient.

Their disadvantage is the pre-distribution phase that

is required prior to ﬁrst usage. The schemes are in-

efﬁcient in dynamic environments but are proposed

in applications where public-key schemes cannot be

used.

5 NETWORK PROTOCOL AND

MANAGEMENT ISSUES

Certain applications of embedded systems, like Wire-

less Sensor Networks, rely on the integrity of the plat-

form for providing trustworthy services (e.g. mea-

surements taken by a sensor). It is therefore essen-

tial to have a method for validating this integrity and

assuring that system components have not been com-

promised. The integrity of the service-requester plat-

form, i.e. control node, must also be validated before

allowing it to allocate resources to the nodes it con-

trols or receive the data these nodes have collected.

In addition, it should be established that these secure

resource management mechanisms will not act as a

bottleneck in service performance. Examples of cur-

rent research on the subject are the WS-Attestation

mechanism (Yoshihama et al., 2007), which enables

Trusted Platform Module (TPM) remote platform at-

testation using web services.

5.1 Secure Resource Management

Inspecting the problem from a higher level, middle-

ware resources should be managed by monitoring

their availability, enforcing a policy based on which

of these resources are assigned, implementing a se-

cure model for the identiﬁcation and authorisation of

requests, as well as an accounting system to track re-

source usage. Most of the above can be found in pro-

tocol Diameter (Calhoun et al., 2003), successor to

RADIUS, which offers strong authentication, autho-

risation, accounting and resource management mech-

anisms. Diameter is already adopted by many IP sys-

tems like in the 3rd Generation Partnership Project

(3GPP).

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

260

5.2 Reputation-based Schemes

Reputation-based schemes are a novel paradigm for

enhancing security in various applications, includ-

ing secure routing and intrusion detection systems for

Mobile Ad Hoc Networks – MANETS (Hatzivasilis

and Manifavas, 2012). These systems are easy to im-

plement, lightweight and can protect a MANET from

a wide variety of attacks.

The basic concept is inspired from social be-

haviour and relies on the cooperation of the nodes.

Much like human interaction, each entity decides to

trust or ignore a new, unknown entity based on the

opinion of its peers about the individual in question.

Consequently, much like in social networks, trustwor-

thy behaviour is encouraged. The three main goals

identiﬁed (Resnick and Zeckhauser, 2002) for reputa-

tion systems are:

• To provide the required information in order to

distinguish between a trustworthy principal and

an untrustworthy one.

• To encourage principals to act in a trustworthy

manner.

• To discourage untrustworthy principals from par-

ticipating in the service.

Reputation-based mechanisms are used in Intru-

sion Detection Systems (IDSs) and provide two main

functionalities: Secure routing and resource manage-

ment. Watchdog and Path-rater (Buchegger et al.,

2004) are the building blocks of such systems. Watch-

dog is a monitoring component and based on its

observations Path-rater ranks the available routing

paths. The main steps in the reasoning process of a

reputation-based scheme are as follows:

1. Gather information.

2. Score and rank.

3. Select entity.

4. Transaction.

5. Reward and punish.

Misbehaviour detection and intrusion detection can

either be distributed, where information about en-

tities’ reputation changes are immediately broad-

cast to the whole network (or local), in which case

each entity decides, based solely on its own data

about the reputation of other nodes. It should be

noted, however, that the latter is not as effective in

terms of speed in detecting and isolating of mali-

cious nodes. Known reputation-based systems for se-

cure routing are IRmIDS (Madhavi and Kim, 2011),

Reputated-ARAN (Abdalrazak and Sawant, 2012)

and CSRAN (Zhang et al., 2008).

While secure routing provides P2P protection,

reputation-based systems for secure resource man-

agement provide end-to-end protection. Such sys-

tems rank resources, providers and consumers. Based

on these values, network entities are able to recog-

nise legitimate providers and resources of good qual-

ity while keeping out selﬁsh and malicious users.

Several reputation-based schemes have been pro-

posed for resource management in P2P and Grid net-

works (Damandeep and Jyotsna, 2012).

5.3 Anonymity and Location Privacy

Location-based applications constitute a rapidly ex-

panding market, owing to the widespread use and

advances in mobile devices and positioning systems

alike. Enhanced reality applications and other simi-

lar services are starting to emerge and are expected to

spread in the coming years. Other examples of such

smart services include location-aware emergency re-

sponse, enhanced entertainment and/or advertisement

services, or even location monitoring of personnel and

ﬂeets of vehicles.

The location of individual users is necessary in or-

der to enable the abovementioned services but, even

though its disclosure may not pose a security risk for

the embedded device itself, said information consti-

tutes sensitive personal data of the user or users as-

sociated with each device and should be handled ac-

cordingly. Disclosure of such information can enable

a malicious user to harass, blackmail or even enter

the individual’s residence (e.g. when he/she is away).

There is on-going research on the subject, including

mechanisms for safeguarding location privacy (Gedik

and Liu, 2008; Zhong and Hengartner, 2008) as well

as reports on the weaknesses of current “sanitisation”

mechanisms (Golle and Partridge, 2009; Gruteser and

Grunwald, 2005).

Literature on this topic includes variations and en-

hancements of a few recurring methods. Anonymi-

sation methods aiming to remove identifying infor-

mation using generalisations and suppressions are the

most popular in the literature, with k-anonymity being

the basic mechanism used, as described in (Zhong and

Hengartner, 2008). The principle of k-anonymity in-

volves the use of a cloaking area, where there are at

least k users in it, and blurs their identities in order to

make each user’s identity indistinguishable from the

rest k − 1 users. In general, there are two important

and mostly unavoidable trade-offs when choosing this

k-value: A trade-off between privacy and quality of

service and a trade-off between privacy and person-

alisation (Liu, 2007). K-anonymity-based schemes

have typically being deployed for privacy-preserving

EmbeddedSystemsSecurityChallenges

261

location monitoring and to allow mobile users to

take advantage of location-based personalised ser-

vices without compromising their privacy (Fysarakis

et al., 2013).

Elementary anonymity schemes (e.g. a pure k-

anonymity scheme) are inadequate if used indepen-

dently and hence they are often combined with aux-

iliary mechanisms, in order to achieve better privacy

safeguards (Golle and Partridge, 2009; Gruteser and

Hoh, 2005; Liu, 2009). Attempting to further en-

hance these basic schemes, the use of personalised k

values is proposed, for systems with context-sensitive

privacy requirements (Gedik and Liu, 2008). More-

over, if combined with l-diversity (Machanavajjhala

et al., 2007), another dimension can be added to k-

anonymity, where l is a set of distinct locations. Other

than the above suggested improvements, the use of

dummy locations (Gupta et al., 2011) and semantic

information (Byoungyoung et al., 2011) are also pro-

posed in the literature, in order to address issues that

are not solved by plain k-anonymity mechanisms.

Pseudonym-based methods are another com-

mon anonymisation theme, involving disposable

pseudonyms for each node in the location ser-

vice (Gruteser and Grunwald, 2005). As the

pseudonyms change over time, they are being used

as temporal identiﬁers, making it hard for potential

attackers to track the users. Silence periods can be in-

troduced to further enhance this concept, as detailed

in (Huang et al., 2005b). Other literature schemes rely

on path perturbation, i.e. trying to cross paths in ar-

eas where at least two users meet (Hoh and Gruteser,

2005).

5.4 Secure Service Discovery,

Composition and Delivery Protocols

Services in distributed networks must be discovered,

composed and delivered in a secure way. The Organi-

sation for the Advancement of Structured Information

Standards (OASIS) has released related standards in-

cluding WS-Security, WS-Policy, WS-Trust and WS-

Secure Conversation which have already been ap-

proved and the current trend is to bring web services

into ESs and it is thus imperative to adopt the afore-

mentioned speciﬁcations.

For this purpose, OASIS developed two standards:

Devices Proﬁle for Web Services (DPWS) and Web

Services Dynamic Discovery (WS-Discovery), which

specify the use of web-services-based communica-

tions in resource-constrained and ad hoc environ-

ments. The proﬁle’s architecture includes hosting and

hosted services. A single hosting service is associ-

ated with each device while the same device may ac-

commodate various hosted services. The latter rep-

resent the device’s various functional elements and

rely on the hosting service for discovery. Discov-

ery services are included as well, enabling devices to

“advertise” their presence on the network and search

for other devices. Metadata exchange services pro-

vide dynamic access to services hosted on a device

and their meta-data. Furthermore, publish/subscribe

eventing services allow other devices to subscribe to

messages provided by a certain service.

Additional research on this area has been con-

ducted by the Service-Oriented Architecture for De-

vices (SOA4D) open-source initiative which facili-

tates the development of service-oriented software

components adapted to the requirements of embed-

ded devices. Web Services for Devices (WS4D) is

another open source initiative, providing a number

of toolkits aimed at developing DPWS-compliant ap-

plications for resource-constrained devices in ad-hoc

networks, maintaining interoperability with regular

W3C-speciﬁed Web Services. A detailed overview

of the WS4D initiative can be found in (Zeeb et al.,

2010).

5.5 Communications Security

Embedded nodes have quite a few choices regard-

ing the protocols they adopt in their communica-

tion stack, depending on their computation capabili-

ties and needs. One of the predominant solutions is

the 6LoWPAN (Hui and Thubert, 2011) stack, i.e.

IPv6 over 802.15.4 (IEEE Standard for Local and

metropolitan area networks, 2011). Such an approach

beneﬁts from the adoption of well-known and stan-

dardised solutions for providing security at the net-

work layer. This is IPsec which, however, has to

utilise compressed header format (Raza et al., 2011;

Rantos et al., 2013a; Rantos et al., 2013b) to ﬁt into

the limited message space provided by IEEE802.15.4,

i.e. a for low-power, low data rate wireless communi-

cation standard for small devices.

The network layer, however, is not the only layer

in the TCP/IP stack where messages can be pro-

tected. The others are application and data link layer.

The corresponding security mechanisms for these two

layers are the Datagram Transport Layer Security –

DTLS protocol (Kothmayr et al., 2012), which is

based on the well-known TLS (Transport Layer Se-

curity) but utilises datagram protocols and the in-

herent security mechanism of IEEE802.15.4 which

is deﬁned in the same standard. All these mech-

anisms were designed to provide at least conﬁden-

tiality, integrity and message authentication, yet they

have slightly different properties.

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

262

Security mechanisms found at the bottom layers

of the communication stack relieve applications from

deploying their own distinct security mechanisms.

However, this comes at a cost. With regards to the

IEEE 802.15.4 security protocol which protects mes-

sages at the data link layer, protection takes place

on a node-by-node basis. This introduces signiﬁ-

cant computational overhead to the nodes which have

to decrypt incoming messages, verify their integrity,

and re-encrypt them, typically using a different set of

keys, prior to forwarding them to the next node. This

process consumes valuable node resources on routing

nodes.

As opposed to 802.15.4, IPsec offers end to end

protection of messages. Therefore, intermediate rout-

ing nodes’ resources are only used for routing packets

and not for message protection. In this sense, security

provided at the network layer can be considered as

a valuable mechanism for low power and lossy net-

works.

IPsec can be either used within such a network

to secure communications among participating nodes

in cases where these are deployed in a hostile envi-

ronment to secure communications among participat-

ing nodes, or between a node and remote party. This

second choice requires utilising a gateway, e.g. sink

node, which can simply forward messages or set up

a tunnel to further protect messages and also provide

communicating node details and trafﬁc ﬂow conﬁden-

tiality. As an example, consider the secure remote

access to an aircraft’s device to control it in case of

an emergency. The aircraft’s gateway can be used

to further protect the message and hide the addresses

of communicating entities, while padding can conceal

communication patterns and characteristics.

Compared to IPsec, DTLS demonstrates similar

characteristics, in terms of end-to-end message pro-

tection, but it suffers from an expensive handshake

mechanism and the inability to cope with applications

that utilise the TCP protocol.

One of the problems one should consider when

deploying one of these three solutions, is the use

of robust key management mechanisms designed for

resource-constrained devices. Traditional public key

cryptography solutions are considered inappropri-

ate in some environments and alternatives, includ-

ing those that utilise lightweight cryptography, ellip-

tic curves and identity based cryptography should be

considered.

6 CONCLUSIONS

This paper provided an overview of the various se-

curity issues in ESs design and implementation. The

particular characteristics of such resource-constrained

devices and the varied requirements of their applica-

tions not only introduce new vulnerabilities but also

intensify existing ones. Moreover, mechanisms and

techniques (e.g. for access control, cryptography, net-

work routing etc.) that would typically be deployed

to secure other types of computing devices are not al-

ways applicable or have limited efﬁcacy in the context

of embedded systems.

Further research is required for establishing se-

cure mechanisms tailored for ESs, in order to address

potential threats to their secure operation, including

those exacerbated by the intrinsic characteristics of

the devices and their application ﬁelds, especially in

the case of critical systems’ applications. What is

more, given the widespread adoption of smart de-

vices in our everyday lives (e.g. smart vehicles, smart

houses, smart clothing), it is important to deal effec-

tively with the inherent security concerns. The chal-

lenge lies with the researchers to put more effort in

the above matters and come up with appropriate so-

lutions, thus helping realise the promise of pervasive

computing and the Internet of Things (IoT).

ACKNOWLEDGEMENTS

This work has been supported by the Greek

General Secretariat for Research and Technology

(GSRT), under the ARTEMIS JU research program

nSHIELD (new embedded Systems arcHItecturE for

multi-Layer Dependable solutions) project. Call:

ARTEMIS-2010-1, Grant Agreement No.: 269317.

REFERENCES

Aad, I., Hubaux, J., and Knightly, E. W. (2008). Im-

pact of denial of service attacks on ad hoc net-

works. IEEE/ACM Transactions on Networking

(TON), 16(4):791–802.

Abdalrazak, T. R. and Sawant, H. K. (2012). Collaborative

trust-based secure routing based ad-hoc routing pro-

tocol. International Journal of Modern Engineering

Research (IJMER), 2(2):95–101.

Akishita, T. and Hiwatari, H. (2012). Very compact hard-

ware implementations of the blockcipher CLEFIA. In

Miri, A. and Vaudenay, S., editors, 18th international

conference on Selected Areas in Cryptography (SAC

’11), volume 7118 of LNCS, pages 278–292, Toronto,

ON, Canada.

EmbeddedSystemsSecurityChallenges

263

Alam, S., Chowdhury, M. M. R., and Noll, J. (2011). In-

teroperability of security-enabled Internet of Things.

Wireless Personal Communications, 61(3):567–586.

Alhaqbani, B. and Fidge, C. (2008). Access control re-

quirements for processing electronic health records.

In Hofstede, A., Benatallah, B., and Paik, H.-Y., ed-

itors, Business Process Management Workshops, vol-

ume 4928 of Lecture Notes in Computer Science,

pages 371–382. Springer Berlin Heidelberg.

Beaulieu, R., Shors, D., Smith, J., Treatman-Clark, S.,

Weeks, B., and Wingers, L. (2013). The SIMON and

SPECK families of lightweight block ciphers. Cryp-

tology ePrint Archive, Report 2013/404.

Bogdanov, A., Knezevic, M., Leander, G., Toz, D., Varici,

K., and Verbauwhede, I. (2011). SPONGENT: A

lightweight hash function. In Preneel, B. and Tak-

agi, T., editors, 13th International Workshop on Cryp-

tographic Hardware and Embedded Systems (CHES

’11), volume 6917 of LNCS, pages 312–325, Nara,

Japan.

Bogdanov, A., Knudsen, L. R., Leander, G., Paar, C.,

Poschmann, A., Robshaw, M. J. B., Seurin, Y.,

and Vikkelsoe, C. (2007). PRESENT: An ultra-

lightweight block cipher. In Paillier, P. and Ver-

bauwhede, I., editors, 9th International Workshop

on Cryptographic Hardware and Embedded Systems

(CHES 2007), volume 4727 of LNCS, pages 450–466,

Vienna, Austria.

Bogdanov, A., Leander, G., Paar, C., Poschmann, A., Rob-

shaw, M. J. B., and Seurin, Y. (2008). Hash func-

tions and RFID tags: Mind the gap. In Oswald, E.

and Rohatgi, P., editors, 10th International Workshop

on Cryptographic Hardware and Embedded Systems

(CHES 2008), volume 5154 of LNCS, pages 283–299,

Washington, D.C., USA.

Boneh, D. and Franklin, M. (2003). Identity-based encryp-

tion from the Weil pairing. SIAM Journal on Comput-

ing, 32(3):586–615. Also appeared in CRYPTO ’01.

Buchegger, S., Tissieres, C., and Le Boudec, J.-Y. (2004).

A test-bed for misbehavior detection in mobile ad-hoc

networks, how much can watchdogs really do? In

6th IEEE Workshop on Mobile Computing Systems

and Applications (WMCSA ’04), pages 102–111, Low

Wood, Lake Windermere, UK.

Byoungyoung, L., Jinoh, O., Hwanjo, Y., and Jong, K.

(2011). Protecting location privacy using location se-

mantics. In 17th ACM SIGKDD International Con-

ference on Knowledge Discovery and Data Mining

(KDD ’11), pages 1289–1297, San Diego, California,

USA.

Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and

Arkko, J. (2003). Diameter base protocol. RFC 3588,

IETF.

Carl, G., Kesidis, G., Brooks, R. R., and Rai, S. (2006).

Denial-of-service attack detection techniques. IEEE

Internet Computing, 10(1):82–89.

Chen, C.-Y. and Chao, H.-C. (2011). A survey of key dis-

tribution in wireless sensor networks. Security and

Communication Networks.

Damandeep, K. and Jyotsna, S. (2012). Proposed p2p trust

and reputation based model to secure grid. IJCA Pro-

ceedings on International Conference on Recent Ad-

vances and Future Trends in Information Technology

(iRAFIT 2012), iRAFIT(2):19–24.

Dan

ek, M., Kadlec, J., Bartosinski, R., and Kohout, L.

(2008). Increasing the level of abstraction in FPGA-

based designs. In Udo, K., editor, International Con-

ference on Field Programmable Logic and Applica-

tions (FPL 2008), pages 5–10, Heidelberg, Germany.

Doomun, M. R. and Soyjaudah, K. M. S. (2009). Analytical

comparison of cryptographic techniques for resource-

constrained wireless security. International Journal of

Network Security, 9(1):82–94.

Doyle, B., Bell, S., Smeaton, A. F., McCusker, K., and

O’Connor, N. (2006). Security considerations and key

negotiation techniques for power constrained sensor

networks. The Computer Journal, 49(4):443–453.

ECRYPT (2008). The eSTREAM project. Available online

at: http://www.ecrypt.eu.org/stream/.

Eisenbarth, T., Kumar, S., Paar, C., Poschmann, A.,

and Uhsadel, L. (2007). A survey of lightweight-

cryptography implementations. IEEE Design & Test,

24(6).

Engels, D., Saarinen, M.-J. O., Schweitzer, P., and Smith,

E. M. (2011). The hummingbird-2 lightweight authen-

ticated encryption algorithm. In Juels, A. and Paar, C.,

editors, 7th Workshop of RFID Security and Privacy

(RFIDSec ’11), volume 7055 of LNCS, pages 19–31,

Amherst, Massachusetts, USA.

Feldhofer, M., Wolkerstorfer, J., and Rijmen, V. (2005).

AES implementation on a grain of sand. IEE Pro-

ceedings on Information Security, 152(1):13–20.

Fysarakis, K., Manifavas, C., Papaefstathiou, I., and

Adamopoulos, A. (2013). A lightweight anonymity

& location privacy service. In IEEE Int. Symposium

on Signal Processing and Information Technology (IS-

SPIT 2013), Athens, Greece. To appear.

Gaj, K., Homsirikamol, E., Rogawski, M., Shahid, R.,

and Sharif, M. U. (2012). Comprehensive evaluation

of high-speed and medium-speed implementations of

ﬁve SHA-3 ﬁnalists using Xilinx and Altera FPGAs.

Cryptology ePrint Archive, Report 2012/368.

Gedik, B. and Liu, L. (2008). Protecting location privacy

with personalized k-anonymity: Architecture and al-

gorithms. IEEE Transactions on Mobile Computing,

7(1):1–18.

Golle, P. and Partridge, K. (2009). On the anonymity of

home/work location pairs. In Tokuda, H., Beigl, M.,

Friday, A., Brush, A. J. B., and Tobe, Y., editors,

7th International Conference on Pervasive Computing

(Pervasive 2009), volume 5538 of LNCS, pages 390–

397, Nara, Japan.

Gruteser, M. and Grunwald, D. (2005). Enhancing location

privacy in wireless LAN through disposable interface

identiﬁers: A quantitative analysis. Mobile Networks

and Applications, 10(3):315–325.

Gruteser, M. and Hoh, B. (2005). On the anonymity of pe-

riodic location samples. In Hutter, D. and Ullmann,

M., editors, 2nd International Conference on Security

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

264

in Pervasive Computing (SPC 2005), volume 3450 of

LNCS, pages 179–192, Boppard, Germany.

Guo, J., Peyrin, T., and Poschmann, A. (2011). The PHO-

TON family of lightweight hash functions. In Rog-

away, P., editor, 31st annual conference on Advances

in cryptology (CRYPTO ’11), volume 6841 of LNCS,

Santa Barbara, CA, USA.

Gupta, K., Yadav, A. S., and Yadav, S. (2011). Location pri-

vacy using user anonymity and dummy locations. In-

ternational Journal of Innovative Technology & Cre-

ative Engineering, 1(10):5–8.

Hatzivasilis, G. and Manifavas, C. (2012). Building trust

in ad hoc distributed resource-sharing networks using

reputation-based systems. In 16th Panhellenic Confer-

ence on Informatics, pages 416–421, Piraeus, Greece.

Hatzivasilis, G., Theodoridis, A., Gasparis, H., Manifavas,

C., and Papaefstathiou, I. (2014). ULCL: An ultra-

lightweight cryptographic library for embedded sys-

tems. In Measurable security for Embedded Comput-

ing and Communication Systems (MeSeCCS 2014),

Lisbon, Portugal. To appear.

Hoh, B. and Gruteser, M. (2005). Protecting location pri-

vacy through path confusion. In 1st International

Conference on Security and Privacy for Emerging Ar-

eas in Communications Networks (SECURECOMM

’05), pages 194–205, Athens, Greece.

Huang, J., Buckingham, J., and Han, R. (2005a). A

level key infrastructure for secure and efﬁcient group

communication in wireless sensor networks. In 1st

IEEE/CreateNet Conference on Security and Privacy

for Emerging Areas in Communication Networks (Se-

cureComm 2005), pages 249–260, Athens, Greece.

Huang, L., Matsuura, K., Yamane, H., and Sezaki, K.

(2005b). Enhancing wireless location privacy using

silent period. In IEEE Wireless Communications and

Networking Conference (WCNC ’05), volume 2, New

Orleans, LA, USA.

Hui, J. and Thubert, P. (2011). Compression format for IPv6

datagrams over IEEE 802.15.4-based networks. RFC

6282, IETF.

IEEE Standard for Local and metropolitan area networks

(2011). IEEE standard for local and metropoli-

tan area networks–Part 15.4: Low-Rate Wireless

Personal Area Networks (LR-WPANs). Avail-

able online at: http://standards.ieee.org/getieee802/

download/802.15.4-2011.pdf.

Kamal, A. A. and Youssef, A. M. (2009). An FPGA im-

plementation of the NTRUEncrypt cryptosystem. In

International Conference on Microelectronics (ICM),

pages 209–212.

Karakoc¸, F., Demirci, H., and Harmanci, A. E. (2013).

ITUbee: A software oriented lightweight block cipher.

In 2nd International workshop on lightweight cryp-

tography for security & privacy (LightSEC 2013).

Karalis, A., Joannopoulos, J. D., and Solja

c, M. (2008).

Efﬁcient wireless non-radiative mid-range energy

transfer. Annals of Physics, 323(1):34–48.

Koscher, K., Czeskis, A., Roesner, F., Patel, S., Kohno, T.,

Checkoway, S., McCoy, D., Kantor, B., Anderson, D.,

Shacham, H., and Savage, S. (2010). Experimental

security analysis of a modern automobile. In IEEE

Symposium on Security and Privacy (SP), pages 447–

462, Oakland, CA, USA.

Kothmayr, T., Schmitt, C., Hu, W., Bruenig, M., and Carle,

G. (2012). A DTLS based end-to-end security archi-

tecture for the Internet of Things with two-way au-

thentication. In IEEE 37th Conference on Local Com-

puter Networks Workshops (LCN Workshops), pages

956–963, Clearwater, FL, USA.

Kuo, C., Luk, M., Negi, R., and Perrig, A. (2007). Message-

in-a-bottle: User-friendly and secure key deployment

for sensor nodes. In 5th International Conference on

Embedded Networked Sensor Systems (SenSys ’07),

pages 233–246, Sydney, Australia.

Kurs, A., Karalis, A., Moffatt, R., Joannopoulos, J. D.,

Fisher, P., and Solja

c, M. (2007). Wireless power

transfer via strongly coupled magnetic resonances.

Science, 317(5834):83–86.

Liu, L. (2007). From data privacy to location privacy: Mod-

els and algorithms. In 33rd international conference

on Very large data bases (VLDB ’07), pages 1429–

1430, Vienna, Austria. VLDB Endowment.

Liu, L. (2009). Privacy and location anonymization

in location-based services. SIGSPATIAL Special,

1(2):15–22.

Machanavajjhala, A., Kifer, D., Gehrke, J., and Venkitasub-

ramaniam, M. (2007). L-diversity: Privacy beyond

k-anonymity. ACM Transactions on Knowledge Dis-

covery from Data, 1(1). Article No. 3.

Madhavi, S. and Kim, T. H. (2011). An intelligent dis-

tributed reputation based mobile intrusion detection

system. International Journal of Computer Science

and Telecommunications, 2(7):53–58.

Manifavas, C., Hatzivasilis, G., Fysarakis, K., and Rantos,

K. (2013). Lightweight cryptography for embedded

systems – A comparative analysis. In 6th Interna-

tions Workshop on Autonomous and Spontaneous Se-

curity (SETOP 2013), volume 8247 of Lecture Notes

in Computer Science, pages 371–382. Springer-Verlag

Berlin Heidelberg, RHUL, Egham, U.K.

Martin, K. M. and Paterson, M. B. (2008). An application-

oriented framework for wireless sensor network key

establishment. Electronic Notes in Theoretical Com-

puter Science, 192(2):31–41.

Naedele, M. (2006). An access control protocol for embed-

ded devices. In 4th International IEEE Conference on

Industrial Informatics (INDIN ’06), pages 565–569,

Singapore.

Oliveira, L. B., Aranha, D. F., Gouv

ea, C. P. L., Scott,

M., C

amara, D. F., L

opez, J., and Dahab, R. (2011).

TinyPBC: Pairings for authenticated identity-based

non-interactive key distribution in sensor networks.

Computer Communications, 34(3):485–493.

Preneel, B. (2009). Research challenges in lightweight

cryptography. Key Note Talk at the 2nd ACM con-

ference on Wireless network security (WiSec ’09).

Rantos, K., Papanikolaou, A., Fysarakis, K., and Manifavas,

C. (2012). Secure policy-based management solu-

tions in heterogeneous embedded systems networks.

EmbeddedSystemsSecurityChallenges

265

In IEEE International conference on Telecomunica-

tions and Multimedia (TEMU 2012), pages 227–232,

Heraklion, Crete, Grece.

Rantos, K., Papanikolaou, A., and Manifavas, C. (2013a).

IPsec over IEEE 802.15.4 for low power and lossy

networks. In 11th ACM International Symposium on

Mobility Management and Wireless Access (MobiWac

2013), pages 59–64, Barcelona, Spain.

Rantos, K., Papanikolaou, A., Manifavas, C., and Papaefs-

tathiou, I. (2013b). IPv6 security for low power and

lossy networks. In Wireless Days 2013 (WD 2013),

Valencia, Spain. To appear.

Raymond, D. R. and Midkiff, S. F. (2008). Denial-of-

service in wireless sensor networks: Attacks and de-

fenses. IEEE Pervasive Computing, 7(1):74–81.

Raza, S., Duquennoy, S., Chung, T., Yazar, D., Voigt, T.,

and Roedig, U. (2011). Securing communication in

6LoWPAN with compressed IPsec. In 7th IEEE In-

ternational Conference on Distributed Computing in

Sensor Systems (DCOSS ’11), pages 1–8, Barcelona,

Spain.

Resnick, P. and Zeckhauser, R. (2002). Trust among

strangers in internet transactions: Empirical analysis

of eBay’s reputation system. In Baye, M. R., edi-

tor, The Economics of the Internet and E-commerce,

volume 11 of Advances in Applied Microeconomics,

pages 127–157. Emerald Group Publishing Limited.

Shibutani, K., Isobe, T., Hiwarati, H., Mitsuda, A., Ak-

ishita, T., and Shirai, T. (2011). Piccolo: An ultra-

lightweight blockcipher. In Preneel, B. and Takagi,

T., editors, 13th International Workshop on Cryp-

tographic Hardware and Embedded Systems (CHES

’11), volume 6917 of LNCS, pages 342–357, Nara,

Japan.

Simplicio, Jr., M. A., Barreto, P. S. L. M., Margi, C. B., and

Carvalho, T. C. M. B. (2010). A survey on key man-

agement mechanisms for distributed wireless sensor

networks. Computer Networks, 54(15):2591–2612.

Smith, R. (2008). Phlashdance, discovering permanent de-

nial of service attacks against embedded systems. Talk

at the EUSecWest Applied Security Conference. Lon-

don.

Stefanidis, K. and Serpanos, D. N. (2008). Implementing

ﬁltering and traceback mechanism for packet-marking

IP-based traceback schemes against DDoS attacks. In

4th International IEEE Conference on Intelligent Sys-

tems (IS ’08), volume 2, pages 14–28, Varna, Bul-

garia.

Szilagyi, C. and Koopman, P. (2009). Flexible multicast au-

thentication for time-triggered embedded control net-

work applications. In IEEE/IFIP International Con-

ference on Dependable Systems & Networks (DSN

’09), pages 165–174, Lisbon, Portugal.

Szilagyi, C. and Koopman, P. (2010). Low cost multicast

authentication via validity voting in time-triggered

embedded control networks. In 5th Workshop on Em-

bedded Systems Security (WESS ’10), pages 10:1–

10:10, Scottsdale, Arizona.

Trusted Platform Module (2009). Information tech-

nology – Trusted Platform Module – Part 1:

Overview. ISO/IEC 11889-1:2009. Available online

at: http://www.trustedcomputinggroup.org/resources/

tpm main speciﬁcation.

Watanabe, D., Ideguchi, K., Kitahara, J., Muto, K., and Fu-

ruichi, H. (2008). Enocoro-80: A hardware oriented

stream cipher. In 3rd International Conference on

Availability, Reliability and Security (ARES 08), pages

1294–1300.

Yoshihama, S., Ebringer, T., Nakamura, M., Munetoh,

S., Mishina, T., and Maruyama, H. (2007). WS-

attestation: Enabling trusted computing on web ser-

vices. In Baresi, L. and Di Nitto, E., editors, Test and

Analysis of Web Services, pages 441–469. Springer

Berlin Heidelberg.

Zeeb, E., Moritz, G., Timmermann, D., and Golatowski, F.

(2010). WS4D: Toolkits for networked embedded sys-

tems based on the devices proﬁle for web services. In

39th International Conference on Parallel Processing

Workshops (ICPPW ’10), pages 1–8, San Diego, CA,

USA.

Zhang, Y., Xu, L., and Wang, X. (2008). A cooperative

secure routing protocol based on reputation system

for ad hoc networks. Journal of Communications,

3(6):43–50.

Zhong, G. and Hengartner, U. (2008). Toward a distributed

k-anonymity protocol for location privacy. In 7th

ACM workshop on Privacy in the electronic society

(WPES ’08), pages 33–38, Alexandria, VA, USA.

PECCS2014-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

266