Distributed Runtime Verification of Cyber-Physical Systems Based on Graph Pattern Matching

Cyber-physical systems process a huge amount of data coming from sensors and other information sources and they often have to provide real-time feedback and reaction. Cyber-physical systems are often critical, which means that their failure can lead to serious injuries or even loss of human lives. Ensuring correctness is an important issue, however traditional design-time verification approaches can not be applied due to the complex interaction with the changing environment, the distributed behavior and the intelligent/autonomous solutions. In this paper we present a framework for distributed runtime verification of cyber-physical systems including the solution for executing queries on a distributed model stored on multiple nodes

On the decidability of linear bounded periodic cyber-physical systems

Cyber-Physical Systems (CPSs) are integrations of distributed computing systems with physical processes via a networking with actuators and sensors, where feedback loops among the components allow the physical processes to affect the computations and vice versa. Although CPSs can be found in several complex and sometimes critical real-world domains, their verification and validation often relies on simulation-test systems rather then automatic methodologies to formally verify safety requirements. In this work, we prove the decidability of the reachability problem for discrete-time linear CPSs whose physical process in isolation has a periodic behavior, up to an initial transitory phase

PALS-Based Analysis of an Airplane Multirate Control System in Real-Time Maude

Distributed cyber-physical systems (DCPS) are pervasive in areas such as aeronautics and ground transportation systems, including the case of distributed hybrid systems. DCPS design and verification is quite challenging because of asynchronous communication, network delays, and clock skews. Furthermore, their model checking verification typically becomes unfeasible due to the huge state space explosion caused by the system's concurrency. The PALS ("physically asynchronous, logically synchronous") methodology has been proposed to reduce the design and verification of a DCPS to the much simpler task of designing and verifying its underlying synchronous version. The original PALS methodology assumes a single logical period, but Multirate PALS extends it to deal with multirate DCPS in which components may operate with different logical periods. This paper shows how Multirate PALS can be applied to formally verify a nontrivial multirate DCPS. We use Real-Time Maude to formally specify a multirate distributed hybrid system consisting of an airplane maneuvered by a pilot who turns the airplane according to a specified angle through a distributed control system. Our formal analysis revealed that the original design was ineffective in achieving a smooth turning maneuver, and led to a redesign of the system that satisfies the desired correctness properties. This shows that the Multirate PALS methodology is not only effective for formal DCPS verification, but can also be used effectively in the DCPS design process, even before properties are verified.Comment: In Proceedings FTSCS 2012, arXiv:1212.657

On the assessment of cyber risks and attack surfaces in a real-time co-simulation cybersecurity testbed for inverter-based microgrids

The integration of variable distributed generations (DGs) and loads in microgrids (MGs) has made the reliance on communication systems inevitable for information exchange in both control and protection architectures to enhance the overall system reliability, resiliency and sustainability. This communication backbone in turn also exposes MGs to potential malicious cyber attacks. To study these vulnerabilities and impacts of various cyber attacks, testbeds play a crucial role in managing their complexity. This research work presents a detailed study of the development of a real-time co-simulation testbed for inverter-based MGs. It consists of a OP5700 real-time simulator, which is used to emulate both the physical and cyber layer of an AC MG in real time through HYPERSIM software; and SEL-3530 Real-Time Automation Controller (RTAC) hardware configured with ACSELERATOR RTAC SEL-5033 software. A human–machine interface (HMI) is used for local/remote monitoring and control. The creation and management of HMI is carried out in ACSELERATOR Diagram Builder SEL-5035 software. Furthermore, communication protocols such as Modbus, sampled measured values (SMVs), generic object-oriented substation event (GOOSE) and distributed network protocol 3 (DNP3) on an Ethernet-based interface were established, which map the interaction among the corresponding nodes of cyber-physical layers and also synchronizes data transmission between the systems. The testbed not only provides a real-time co-simulation environment for the validation of the control and protection algorithms but also extends to the verification of various detection and mitigation algorithms. Moreover, an attack scenario is also presented to demonstrate the ability of the testbed. Finally, challenges and future research directions are recognized and discussed

Sensor Verification for Cyber-Physical Models of Power Systems

This project explores the ways that data from sensors in power systems can be authenticated by enhancing the security of power systems from a cyber-physical point of view. This is a continuation of the work for the NSF project “CPS: Synergy: Collaborative Research: Distributed Just-Ahead-Of-Time Verification of Cyber-Physical Critical Infrastructure.” Adversaries who gain access to a cyber-physical system can cause significant physical damage and financial loss by injecting false data into a sensor node. Identifying adversarial action in a system can mitigate unsafe actions made based off of bad data. The technique presented in this work combines topology analysis with real-time probing to create a measure of trustworthiness of sensors in a system. A previously developed tool called Cyber Physical Security Assessment (CyPSA) gives each node a topology vulnerability score based on the cyber accessibility and potential physical impact should it be compromised. We develop a real-time vulnerability score by simulating attack and non-attack scenarios with PowerWorld. The data from these simulations is processed in MATLAB. Results show improved attack detection over current methods. The measure of trustworthiness developed will improve attack detection in power systems, and it may be used to help prevent a system from entering an unstable state

Sensor Verification for Cyber-Physical Models of Power Systems

This project explores the ways that data from sensors in power systems can be authenticated by enhancing the security of power systems from a cyber-physical point of view. This is a continuation of the work for the NSF project “CPS: Synergy: Collaborative Research: Distributed Just-Ahead-Of-Time Verification of Cyber-Physical Critical Infrastructure.” Adversaries who gain access to a cyber-physical system can cause significant physical damage and financial loss by injecting false data into a sensor node. Identifying adversarial action in a system can mitigate unsafe actions made based off of bad data. The technique presented in this work combines topology analysis with real-time probing to create a measure of trustworthiness of sensors in a system. A previously developed tool called Cyber Physical Security Assessment (CyPSA) gives each node a topology vulnerability score based on the cyber accessibility and potential physical impact should it be compromised. We develop a real-time vulnerability score by simulating attack and non-attack scenarios with PowerWorld. The data from these simulations is processed in MATLAB. Results show improved attack detection over current methods. The measure of trustworthiness developed will improve attack detection in power systems, and it may be used to help prevent a system from entering an unstable state

사이버-물리 시스템을 위한 기능적/시간적 정확성 보장 시뮬레이션 기법

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 이창건.When developing a Cyber-Physical System (CPS), simulators are commonly used to predict the final performance of the system at the design phase. However, current simulation tools do not consider timing behaviors of the cyber-system such as varying execution times and task preemptions. Thus, their control performance predictions are far different from the real performance, and this leads to enormous time and cost for a system development, because multiple re-design and re-implementation phases are required, until an acceptable system configuration is determined. Motivated by this limitation, this dissertation proposes functionally and temporally correct simulation for the cyber-side of a CPS. The key idea of the proposed approach is to keep the data and time correctness only at the physical interaction points to maximally enjoy the freedom of scheduling simulated jobs. For this, we transform the simulation problem to a real-time job scheduling problem with precedence constraints necessary for the functional and temporal correctness. Then, we propose an efficient scheduling algorithm for the functionally and temporally correct real-time simulation. The proposed approach significantly improves the real-time simulation capacity of the state-of-the-art simulation methods while keeping the functional and temporal correctness. Our evaluation through both synthetic workload and actual implementation confirms both high accuracy and high efficiency of our approach compared with other state-of-the-art methods.1 Introduction 1 1.1 Motivation and Objective 1 1.2 Approach 3 1.3 Contributions 8 1.4 Organization 8 2 Related Work 10 2.1 Design and Verification of Cyber-Physical Systems 10 2.2 Verification Approaches 12 2.2.1 Model-Based Simulations 12 2.2.2 Cycle-Accurate Simulations and Host-Compiled Simulations 14 2.2.3 Real-Time Execution Platforms 15 2.2.4 Distributed Simulations 16 2.3 Job Scheduling Approaches 17 3 System Model and Problem Description 22 3.1 Description on the real cyber-system 23 3.2 Description on the simulated cyber-system 27 3.3 Formal definition of the simulation problem 28 4 Real-Time Simulation for Deterministic Cyber-Systems 31 4.1 Introduction 31 4.2 Construction of Offline Guider 31 4.3 Online Progressive Scheduling of Simulated Jobs 34 4.4 Evaluation 38 5 Real-Time Simulation for Non-Deterministic Cyber-Systems 45 5.1 Introduction 45 5.2 Overview of Approach 45 5.3 Construction of Offline Guider 50 5.4 Online Progressive Scheduling of Simulated Jobs 63 5.5 Evaluation 74 5.5.1 Evaluation Using Synthesized Cyber-Systems 78 5.5.2 Implementation 86 6 Practical Discussions 95 6.1 Data Exchange Delay 95 6.2 Simulation Overhead 97 6.2.1Offline Overhead 97 6.2.2 Online Overhead 100 6.3 Other Useful Features 100 7 Extension for Multicore Simulation PC 102 8 Conclusion 108 8.1 Summary 108 8.2 Future Work 108 References 110Docto

Testing the Verification and Validation Capability of a DCP-Based Interface for Distributed Real-Time Applications

Cyber–physical systems (CPS) integrate diverse elements developed by various vendors, often dispersed geographically, posing significant development challenges. This paper presents an improved version of our previously developed co-simulation interface based on the non-proprietary Distributed Co-Simulation Protocol (DCP) standard, now optimized for broader hardware platform compatibility. The core contributions include a demonstration of the interface’s hardware-agnostic capabilities and its straightforward adaptability across different platforms. Furthermore, we provide a comparative analysis of our interface against the original DCP. It is validated via various X-in-the-Loop simulations, reinforcing the interface’s versatility and applicability in diverse scenarios, such as distributed real-time executions, verification and validation processes, or Intellectual Property protection.This research was funded by Basque Government through the ELKARTEK programme under the AUTOTRUS project (grant number KK-2023/00019) and the European Commission’s Horizon Europe programme under the METASAT project (grant 101082622)

Wide-Area Time-Synchronized Closed-Loop Control of Power Systems And Decentralized Active Distribution Networks

The rapidly expanding power system grid infrastructure and the need to reduce the occurrence of major blackouts and prevention or hardening of systems against cyber-attacks, have led to increased interest in the improved resilience of the electrical grid. Distributed and decentralized control have been widely applied to computer science research. However, for power system applications, the real-time application of decentralized and distributed control algorithms introduce several challenges. In this dissertation, new algorithms and methods for decentralized control, protection and energy management of Wide Area Monitoring, Protection and Control (WAMPAC) and the Active Distribution Network (ADN) are developed to improve the resiliency of the power system. To evaluate the findings of this dissertation, a laboratory-scale integrated Wide WAMPAC and ADN control platform was designed and implemented. The developed platform consists of phasor measurement units (PMU), intelligent electronic devices (IED) and programmable logic controllers (PLC). On top of the designed hardware control platform, a multi-agent cyber-physical interoperability viii framework was developed for real-time verification of the developed decentralized and distributed algorithms using local wireless and Internet-based cloud communication. A novel real-time multiagent system interoperability testbed was developed to enable utility independent private microgrids standardized interoperability framework and define behavioral models for expandability and plug-and-play operation. The state-of-theart power system multiagent framework is improved by providing specific attributes and a deliberative behavior modeling capability. The proposed multi-agent framework is validated in a laboratory based testbed involving developed intelligent electronic device prototypes and actual microgrid setups. Experimental results are demonstrated for both decentralized and distributed control approaches. A new adaptive real-time protection and remedial action scheme (RAS) method using agent-based distributed communication was developed for autonomous hybrid AC/DC microgrids to increase resiliency and continuous operability after fault conditions. Unlike the conventional consecutive time delay-based overcurrent protection schemes, the developed technique defines a selectivity mechanism considering the RAS of the microgrid after fault instant based on feeder characteristics and the location of the IEDs. The experimental results showed a significant improvement in terms of resiliency of microgrids through protection using agent-based distributed communication