Page 189 - Trust in ICT 2017

Trust in ICT 3

– Antonym: The articulation of trust context in two entities may differ based on the opposing
perspective. For example, entity A trusts entity B in the context of “buying” book, however from
entity B to entity A the context is “selling” book.
– Asynchrony: The time period of trusting relationship may be defined differently between the
entities. For example, entity A trusts entity B for 3 years, however, entity B may think that the trust
relationship only last for the last 1 year.
– Gravity: The degree of seriousness in trust relationships may differ between the entities. For
example, entity A may think that its trust with entity B is important, however, entity B may think it
differently.
• Trust among multiple trust domains
Trust domain is a set of information and associated resources consisting of users, networks, data repositories,
and applications (or services) that manipulate the data in those data repositories. For providing a trust-based
service, multiple trust domains are involved. Different trust domains may share the same social-cyber-
physical components. Also, a single trust domain may employ various levels of trust, depending on what the
users need to know and the sensitivity of the information and associated resources [ITU-T M.3410].
– Quality of Trust (QoT): Due to the diversity of applications and their inherent differences in nature,
trust is hard to be formalized in a general setting. However, it is important to quantify a level of trust
in ICT infrastructures. A certain level of trust should be derived from the associated devices, services,
applications and users of trust. The level of trust can be measured and classified objectively or
subjectively. The concept of QoT, which is similar with QoS as an objective manner (e.g., measured
quantitatively) or QoE as a subjective manner (e.g., counted qualitatively), represents different
classes in terms of levels of trust in multiple domains (e.g., physical, cyber, and social domains). It
can be used to understand the degree of trust among multiple trust domains.
– Trust Level Agreement (TLA): Depending on what QoT the users need, including those related to
sensitivity of information and associated resources, there may be a lot of TLAs – similar to the
concept of Service Level Agreement (SLA).
Figure 7-2 shows an example of different classes of QoT among multiple trust domains in an ICT
infrastructure. A service domain may consist of multiple trust domains (e.g., three trust domains in this
figure). Depending on levels of trust for each component, a trust domain may have different classes of QoT.
For example, trust domain A provides physical trust (QoT Class 1), trust domain B provides physical and cyber
trust (QoT Class 2), and trust domain C provides physical, cyber and social trust (QoT Class 3). Then, TLA is
established, based on the agreement of all involved trust domains using the QoT information to provide a
trust-based ICT service.

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