Opacity of Networked Discrete Event Systems

Yang, Jingkai; Deng, Weilin; Cheng, Jia-Hui; Qiu, Daowen

doi:10.1109/cdc40024.2019.9030250

Cited by 8 publications

(4 citation statements)

References 18 publications

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“…However, for networked control systems, the information transmission between controllers and plants in the feedback loops may also be released to the intruder. There are some very recent works on the verification of opacity for networked control systems using finite-state models; see, e.g., [222,214,238,107,213]. However, existing works on formal verification of networked control system mainly focus on the mission requirements [231,69,146,28] and to the best of our knowledge, there is no result on formal verification of opacity for general networked CPS.…”

Section: 4mentioning

confidence: 99%

Secure-by-Construction Synthesis of Cyber-Physical Systems

Liu¹,

Trivedi²,

Yin³

2022

Preprint

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Correct-by-construction synthesis is a cornerstone of the confluence of formal methods and control theory towards designing safety-critical systems. Instead of following the time-tested, albeit laborious (re)design-verify-validate loop, correct-by-construction methodology advocates the use of continual refinements of formal requirements-connected by chains of formal proofs-to build a system that assures the correctness by design. A remarkable progress has been made in scaling the scope of applicability of correct-byconstruction synthesis-with a focus on cyber-physical systems that tie discrete-event control with continuous environment-to enlarge control systems by combining symbolic approaches with principled state-space reduction techniques. Unfortunately, in the security-critical control systems, the security properties are verified ex post facto the design process in a way that undermines the correct-by-construction paradigm. We posit that, to truly realize the dream of correct-by-construction synthesis for security-critical systems, security considerations must take center-stage with the safety considerations. Moreover, catalyzed by the recent progress on the opacity sub-classes of security properties and the notion of hyperproperties capable of combining security with safety properties, we believe that the time is ripe for the research community to holistically target the challenge of secure-by-construction synthesis. This paper details our vision by highlighting the recent progress and open challenges that may serve as bricks for providing a solid foundation for secure-by-construction synthesis of cyber-physical systems.The revolution in miniaturized communication devices in the beginning of this millennium contributed towards a revolution in the internet-of-things (IoT) and the networked systems woven around them: the cyber-physical systems (CPS). CPS are marked by a close-knit interaction of discrete computation and continuous control over a network and are playing critical roles in virtually every aspect of our modern experience ranging from consumer electronics to implantable medical devices, from smart cars to smart hospitals, and from controlling our power systems to safeguarding our nuclear rectors. These systems are clearly safety-critical as a bug in their design could be life threatening, but given their societal implications, they are also security-critical where a bug in their design may have the potential to jeopardize the privacy, trust, and economic interests of society built around them." We believe that the security considerations should be elevated as primary design drivers along with safety ones to tackle the design challenge of modern CPS and call for a need to expand the correct-byconstruction paradigm of designing safety-critical systems to encompass security: we call this paradigm secure-by-construction. This paper synthesizes ideas from three research communities: discrete event systems (DES), control systems (CS), and formal methods (FM) to pose and study central problems supporting...

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Section: 4mentioning

confidence: 99%

Secure-by-Construction Synthesis of Cyber-Physical Systems

Liu¹,

Trivedi²,

Yin³

2022

Preprint

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“…In addition, by modeling the system as a probabilistic finite state automaton, [17]- [20] investigate the verification of opacity in the context of stochastic DES, where the violation of opacity is characterized by the probability, not a binary value (0 or 1) as in the case of a non-stochastic DES. Furthermore, the investigation on the verification of opacity has also been extended to networked DES recently in [21], [22], where the communication delays and losses in the observation channel and the control channel have been taken into consideration. Readers could refer to [23], [24] for a more comprehensive literature review.…”

Section: Introductionmentioning

confidence: 99%

Privacy-Preserving Supervisory Control of Discrete-Event Systems via Co-Synthesis of Edit Function and Supervisor for Opacity Enforcement and Requirement Satisfaction

Tai,

Lin,

Zhu

et al. 2021

Preprint

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This paper investigates the problem of co-synthesis of edit function and supervisor for opacity enforcement in the supervisory control of discrete-event systems (DES), assuming the presence of an external (passive) intruder, where the following goals need to be achieved: 1) the external intruder should never infer the system secret, i.e., the system is opaque, and never be sure about the existence of the edit function, i.e., the edit function remains covert; 2) the controlled plant behaviors should satisfy some safety and nonblockingness requirements, in the presence of the edit function. We focus on the class of edit functions that satisfy the following properties: 1) the observation capability of the edit function in general can be different from those of the supervisor and the intruder; 2) the edit function can implement insertion, deletion, and replacement operations; 3) the edit function performs bounded edit operations, i.e., the length of each string output of the edit function is upper bounded by a given constant. We propose an approach to solve this cosynthesis problem by modeling it as a distributed supervisor synthesis problem in the Ramadge-Wonham supervisory control framework. By taking the special structure of this distributed supervisor synthesis problem into consideration and to improve the possibility of finding a non-empty distributed supervisor, we propose two novel synthesis heuristics that incrementally synthesize the supervisor and the edit function. The effectiveness of our approach is illustrated on an example in the enforcement of the location privacy.

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“…Furthermore, when a given system is not opaque, its opacity enforcement problem has been extensively investigated using a variety of techniques, including supervisory control [14,15,16], insertion or edit functions [17,18,19,20], dynamic observers [21], etc. Recently, verification and/or enforcement of opacity have been extended to other classes of settings, including Petri nets [22,23,24], stochastic systems [25,26,27], modular systems [28], networked systems [29,30], etc. In recent literature [31,32], the authors studied opacity preserving (bi)simulation relations using an abstractionbased technique for nondeterministic transition systems and metric systems, respectively.…”

Section: Introductionmentioning

confidence: 99%

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

Han¹,

Zhang²,

Zhang³

et al. 2021

Preprint

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Opacity, as an important property in information-flow security, characterizes the ability of a system to keep some secret information from an intruder. In discrete-event systems, based on a standard setting in which an intruder has the complete knowledge of the system's structure, the standard versions of current-state opacity and initial-state opacity cannot perfectly characterize high-level privacy requirements. To overcome such a limitation, in this paper we propose two stronger versions of opacity in partially-observed discrete-event systems, called strong current-state opacity and strong initial-state opacity. Strong current-state opacity describes that an intruder never makes for sure whether a system is in a secret state at the current time, that is, if a system satisfies this property, then for each run of the system ended by a secret state, there exists a non-secret run whose observation is the same as that of the previous run. Strong initial-state opacity captures that the visit of a secret state at the initial time cannot be inferred by an intruder at any instant. Specifically, a system is said to be strongly initial-state opaque if for each run starting from a secret state, there exists a non-secret run of the system that has the same observation as the previous run has. To verify these two properties, we propose two information structures using a novel concurrent-composition technique, which has exponential-time complexity O(|X| 4 |Σo||Σuo||Σ|2 |X| ), where |X| (resp., |Σ|, |Σo|, |Σuo|) is the number of states (resp., events, observable events, unobservable events) of a system.

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Opacity of Networked Discrete Event Systems

Cited by 8 publications

References 18 publications

Secure-by-Construction Synthesis of Cyber-Physical Systems

Secure-by-Construction Synthesis of Cyber-Physical Systems

Privacy-Preserving Supervisory Control of Discrete-Event Systems via Co-Synthesis of Edit Function and Supervisor for Opacity Enforcement and Requirement Satisfaction

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

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