Strong current-state and initial-state opacity of discrete-event systems

Opacity, as an important property in information-flow security, characterizes the ability of a system to keep some secret information from intruder. In discrete-event systems, based on standard setting which intruder has complete knowledge system’s structure, versions current-state opacity and initial-state cannot perfectly characterize higher-level privacy requirements. To overcome such limitation, this paper we propose two stronger called strong for partially-observed nondeterministic finite-state automata. Strong (resp., initial-state) describes that each run ending starting) at state, there exists non-secret whose observation is same previous run. Then structure using novel concurrent-composition technique verify opacity, time complexity O((|Σ||X|2+|Σo||X∖XS|2(1+|Σuo|))2|X∖XS|), where |X| |Σ|, |Σo|, |Σuo|, |X∖XS|) number states events, observable unobservable states) automaton. Finally, proposed also used check infinite-step lower than one literature.