Opacity for switched linear systems: Notions and characterization
Bhaskar Ramasubramanian, Rance Cleaveland, Steven I. Marcus · 2017
A switched system consists of a finite number of subsystems and a rule that orchestrates switching among them. We develop notions of opacity for discrete-time switched linear systems. We distinguish between cases when the secret is specified as a set of initial modes, a set of initial states, or a combination of the two. The novelty of our schemes is in the fact that we place restrictions on: i) the allowed transitions between modes (specified by a directed graph), ii) the number of allowed changes of modes (specified by lengths of paths in the directed graph), and iii) the dwell times in each mode. Each notion of opacity is characterized in terms of allowed switching sequences and sets of reachable states and/ or modes. Finally, we present algorithmic procedures to verify these notions, and provide bounds on their computational complexity.