Internet of Things – Architecture © - 97 -
Trust-evaluation mechanisms: They define a coherent and safe
methodology for computing the trustworthiness degree of a subject within
the system. Evaluation mechanisms are based on information priorly
collected on the given subject. Depending on the application scenario,
this information can be obtained by direct experiences with the subject,
witness information on the subject coming from other members of a
community, social-network analysis providing sociological information on
the subject and so on. A trust-evaluation mechanism must take into
account the source of the information on which the trust value is being
computed, i.e. the trustworthiness of the source itself, and carefully
weight its information accordingly in computing the final trust value; Behaviour policies: They regulate the ways two subjects within the
same Trust Model domain interact according to their trustworthiness
value. They define how subjects that use the system may interact with
other subject. E.g., if a wireless sensor A is asked to handle a multi-hop
message coming from a sensor B with a very low trust value, Sensor A
might decide, according to the behaviour policies defined by the Trust
Model, to not accept the message from Sensor B. Though it is not
recommended, a Trust Model can define specific behaviours for
interacting with subjects whose trust-value cannot be computed within
that model; Trust anchor: It is a subject trusted by default (possibly after
authentication) by all subjects using a given Trust Model, and exploited in
the evaluation of third parties‘ trustworthiness. In the IoT environment the
trust anchor can either be local to a given subnetwork—running on a
node in the same peripheral network, e.g. a gateway—or a global and
centralised device that is deployed on the Internet; Federation of trust: It delineates the rules under which trust
relationships among systems with different Trust Models can be defined.
The federation of trust is essential in order to provide interoperability
between subjects that use different Trust Models. The federation of trust
becomes particularly important within an IoT system deployed on a large
scale, where the coexistence of many different Trust Models it is very
likely; M2M support: The interaction among autonomous machines is deemed
very common in IoT systems. Prior dynamically identifying and accessing
resources of one-another, these machines should be able to
autonomously, according to the specifics in the Trust Model, evaluate the
trustworthiness of each other.