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Towards a Platform for Widespread Embedded Intelligence - ERCIM

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embedded devices, but threaten the<br />

devices' dependability and security properties.<br />

In the context of an open component-based<br />

system that supports unmanaged<br />

upgrading and extension (changing<br />

the software configuration), it is possible<br />

that component-based devices may host<br />

unstable components that could negatively<br />

affect the devices' dependability.<br />

Here, the most risky scenario is the download<br />

of new components to extend the<br />

system's capabilities; this exposes the system's<br />

internals to potentially malicious<br />

components that may compromise the<br />

system's overall security.<br />

Recent research indicates that the use of<br />

Trust Management can be a useful tool<br />

when addressing the dependability and<br />

security concerns encountered in distributed<br />

and embedded systems.<br />

The Trust4All project has embraced this<br />

emerging topic and investigated its application<br />

in the context of component-based<br />

embedded systems. Our approach has<br />

been to extend the component-based<br />

middleware, first developed within the<br />

EU-ITEA Robocop and Space4U projects,<br />

to include a Trustworthiness<br />

Management Framework (TMF), as<br />

shown in the figure. This framework provides<br />

low-level mechanisms that can be<br />

used to control and en<strong>for</strong>ce components'<br />

behaviour, based upon established<br />

Trustor-Trustee relationship. The goal of<br />

TMF is to support easy and late (possibly<br />

runtime) integration of components and<br />

still have dependability and security<br />

properties that are satisfactory to the user.<br />

The TMF design addresses the following<br />

challenges:<br />

• The TMF acts on behalf of Trustors<br />

and explicitly takes their trust requirements<br />

into account.<br />

• The TMF makes use of 'metric<br />

sources' to monitor and report on the<br />

system's overall behaviour.<br />

• The TMF makes use of 'actuators' to<br />

control a Trustee's mode of operation,<br />

thereby influencing the system's<br />

behavioural characteristics.<br />

• The TMF makes use of the Space4U<br />

Resource Management Framework to<br />

decide whether a component's<br />

requested mode of operation should be<br />

allowed from a resource consumption<br />

point of view.<br />

A core part of the TMF is the<br />

Trustworthiness Evaluation Function<br />

(TEF), which is responsible <strong>for</strong> calculating<br />

the trustworthiness of a component/Trustee.<br />

It can be parameterised<br />

with Trustor-specific dependability and<br />

security requirements. By analysing a<br />

Trustee's 'estimated quality attributes'<br />

and recommendations, the TEF can evaluate<br />

a component's 'present trustworthiness'<br />

(or compliance) in terms of the<br />

degree to which it satisfies the Trustor's<br />

stated dependability and security<br />

requirements. Through analysis of component's<br />

behaviour, the TEF calculates<br />

(utilising Subjective Logic) the 'believed<br />

trustworthiness' of a component in terms<br />

of the following aspects:<br />

• Benignity: the belief that the component<br />

will continue to satisfy the<br />

Trustor's requirements,<br />

• Stability: the belief that the Trustee's<br />

behavioural qualities of will remain<br />

within a given neighbourhood.<br />

The triple of compliance, benignity, and<br />

stability is used to make control decisions<br />

that regulate the system's overall<br />

dependability and security characteristics.<br />

For example, when a component<br />

with positive compliance begins to show<br />

a reducing benignity, the TMF may<br />

decide to 'wrap' the component in an<br />

attempt to minimise its potential impact<br />

on the system, since it is displaying<br />

increasingly less-compliant behaviour.<br />

Similarly, when there is a strong disbelief<br />

in stability, this may indicate a need<br />

SPECIAL THEME: <strong>Embedded</strong> <strong>Intelligence</strong><br />

The Trust Management Framework, as part of the middleware of the embedded<br />

component-based devices, ensures the dependability of the system, when a new<br />

component is added.<br />

to re-evaluate the component's estimated<br />

quality attributes and, as a consequence,<br />

re-evaluate its compliance.<br />

The project began in July 2005 and will<br />

run <strong>for</strong> two years. Its ef<strong>for</strong>ts are now<br />

moving from research and design<br />

towards implementation and construction<br />

of demonstrators in the domains of<br />

consumer electronics, mobile devices,<br />

and domotics.<br />

Many companies and researchers collaborate<br />

in Trust4All: CWI, Océ<br />

–Technologies, Philips Research (project<br />

coordinator), Telematica Instituut,<br />

Eindhoven University of Technology<br />

(TU/e), Univ. Leiden (the Netherlands).<br />

Nokia, Solid In<strong>for</strong>mation Technologies,<br />

VTT (Finland), ESI, FAGOR,<br />

IKERLAN-Electrónica, Robotiker, and<br />

Visual Tools (Spain).<br />

Links:<br />

http://www.research.philips.com<br />

http://www.telin.nl<br />

http://www.win.tue.nl/trust4all<br />

Please contact:<br />

Gabriele Lenzini, Telematica Instituut,<br />

The Netherlands<br />

Tel: + 31 53 4850463<br />

E-mail: Gabriele.Lenzini@telin.nl<br />

Johan Muskens, Philips Research Europe,<br />

The Netherlands<br />

Tel: + 31 40 2742491<br />

E-mail: Johan.Muskens@philips.com<br />

Picture: Telematica Instituut and Philips.<br />

<strong>ERCIM</strong> News No. 67, October 2006 49

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