The Information System for Critical Use Access Process Dependability Modeling

Objective reasons for the introduction of multi-server architecture for the creation of information systems for critical use (ISCU) have led to complications in ensuring their confidentiality, as a component of information security, and in assessment of their reliability. The paper proposes to comprehensively consider these characteristics of the ISCU within the framework of the integral qualitative characteristic of dependability. In order to assess the reliability of the procedure for access to ISCU, authors proposed a Markov model of the dependence of the functional capacity of ISCU on the influence of negative factors. This model describes a set of ISCU states and allows to get an analytical expressions to calculate the probabilities for the presence of ISCU in the corresponding states at selected moments of time depending on the probability of occurrence of negative factors and configurations of the access separation subsystem that controls the authorization process. For practical application of the model the appropriate methodology is developed. This methodology allowed, in particular, to confirm the adequacy of the model using standard methods of the planning experiment theory, including Fisher's criterion.