Security of Safety Important I&C Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 243

• High Conidence: Ability of correct esti-
mation of services quality, i.e. deinition of
trust level to the service.
• Maintainability: Ability to undergo modi-
ications and repairs.

trustworthiness, and we denoted their two-way
influence (Kharchenko, V. et al., 2012,b).
We should note that such particular attributes
may be defined for each of primary attributes,
thus, representing hierarchical structure of safety
important system's generic attributes set. More-
over, those secondary and further attributes may
turn to be common for different primary attributes
due to their incomplete “orthogonality.”

• Security: The protection from unauthor-

ized access, use, disclosure, disruption,
modiication, or destruction in order to
provide conidentiality, integrity, and

availability.

Metrics

In turn, safety attribute of a safety important
system can have some particular (or secondary)
attributes depending on exact system, environment
and conditions that have influence on the primary
attribute. Here, we distinguished the following
attributes (see Figure 2): reliability, security and

Thus, we can state that a set of safety important
system attributes can be represented in a form of
i-level hierarchical model, and each of i levels
contains ki attributes. As an example, Figure 3
represents an element of last two levels of a safety

Figure 2. Taxonomy of safety attribute

Figure 3. Levels of safety important system attributes hierarchy