On observability of discrete-event systems
Information Sciences: an International Journal - Robotics and Automation/Control Series
The dining cryptographers problem: unconditional sender and recipient untraceability
Journal of Cryptology
Untraceable electronic mail, return addresses, and digital pseudonyms
Communications of the ACM
Coordinated Decentralized Protocols for Failure Diagnosisof Discrete Event Systems
Discrete Event Dynamic Systems
ESORICS '96 Proceedings of the 4th European Symposium on Research in Computer Security: Computer Security
Discrete Event Dynamic Systems
Opacity generalised to transition systems
International Journal of Information Security
Dynamic Observers for the Synthesis of Opaque Systems
ATVA '09 Proceedings of the 7th International Symposium on Automated Technology for Verification and Analysis
Modelling Opacity Using Petri Nets
Electronic Notes in Theoretical Computer Science (ENTCS)
Introduction to Discrete Event Systems
Introduction to Discrete Event Systems
Opacity of discrete event systems and its applications
Automatica (Journal of IFAC)
Preserving secrecy under refinement
ICALP'06 Proceedings of the 33rd international conference on Automata, Languages and Programming - Volume Part II
On the verification of intransitive noninterference in mulitlevel security
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics
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Opacity is a confidentiality property that captures whether an intruder can infer a "secret" of a system based on its observation of the system behavior and its knowledge of the system's structure. In this paper, we study four notions of opacity: language-based opacity, initial-state opacity, current-state opacity, and initial-and-final-state opacity. Initial-and-final-state opacity is a new opacity property introduced in this paper, motivated by secrecy considerations in anonymous network communications; the other three opacity properties have been studied in prior work. We investigate the relationships between these opacity properties. In this regard, a complete set of transformation algorithms among the four notions is provided. We also propose a new, more efficient test for initial-state opacity based on the use of reversed automata, and present a trellis-based test for the new property of initial-and-final state opacity. We then study the notions of initial-state opacity, current-state opacity, and initial-and-final-state opacity in the context of a new coordinated architecture where two intruders work as a team in order to infer the secret. In this architecture, the intruders have the capability of combining their respective state estimates at a coordinating node. In each case, a characterization of the corresponding notion of "joint opacity" and an algorithmic procedure for its verification are provided.