Page 257 - Trust in ICT 2017

Trust in ICT 5

Figure 5 – Trust relationship model

In trust relationship model, cyber objects and virtual objects are linked with physical things and social entities
as shown in Figure 5. A virtual physical object is the virtualized model of physical thing through physical
interfaces such as sensors and actuators. The cyber objects are modelled as physical objects and logical
objects. The physical object is modelled of hardware device and equipment and the logical object is modelled
by the corresponding software. A virtual social object is the virtual model of social entity through applications
and user interfaces. Virtual physical objects, cyber objects, and virtual social objects can be seen as the trust
components for physical trust, cyber trust, and social trust, respectively.

Based on the model of physical, cyber, and social trust components, there are various trust relationships in
ICT infrastructures and services horizontally: social-social trust relationship, cyber-cyber trust relationship,
and physical-physical trust relationship. Also, trust relationships of trust components are established vertically
among different types of trust components: social-cyber trust relationship, cyber-physical trust relationship,
and social-physical trust relationship. When a trust component establishes trust relationships with others,
the component gets trust information from others.

7.4 Trust evaluation for trust provisioning

To compare the degree of trust of different entities, a method is needed to measure, quantify, and assess
trust. Trust evaluation is the way from input data of various sources to calculate trust for the target services
or objects. Three types of trust information are defined as follows.
– Trust attribute: Trust attributes represent characteristics of an entity (include direct and indirect
trust), which consists of qualitative and quantitative attributes. Trust attributes refer to properties
and features of an entity that can be trusted upon. Qualitative attributes need the quantization
process to accumulate with quantitative attributes.

– Trust indicator: Trust indicators are used to calculate a trust index by combining qualitative and
quantitative attributes of trust. Objective trust indicators stand for features that represent
trustworthiness of an entity quantitatively. Subjective trust indicators reflect subjective or personal
attributes of trust entities. The trust indicators are calculated at the measurement instance of their
trustworthiness since their values are changing as time goes.

– Trust index: A trust index is a composite and relative value that combines multiple trust indicators
into one benchmark measure for representing trustworthiness of an entity, which is similar to ICT
development index or stock market index. A trust index is a comprehensive accumulation of the

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