Vol. 25, No 3, 2021 < Volumes
(ISSN 1428-6394)

Contents:

  • F. Gonzalez, M. Rusinkiewicz and J. Zalewski A Model for Intelligent Protection of Critical Computer Systems   abstract | full text
  • N. Subramanian Root Cause Analysis of Cybersecurity Incidents on Pipelines Using the NFR Approach   abstract | full text
  • J. van Katwijk Digital Audio Broadcasting   abstract | full text
  • M. Kłopotek, S. Wierzchoń and R. Kłopotek Weighted Laplacians of Grids and Their Application for Inspection of Spectral Graph Clustering Methods   abstract | full text
  • R. Sanz, J. Bermejo, M. Rodríguez and E. Aguado The Role of Knowledge in Cyber-Physical Systems of Systems   abstract | full text

Abstracts:

hF. Gonzalez, M. Rusinkiewicz and J. Zalewski A Model for Intelligent Protection of Critical Computer Systems

Abstract: We propose a unified model for the enforcement of safety and security of cyber-physical systems in critical applications. We argue that the need for resilience of a critical system requires simultaneous protection from hazards (safety) and from unauthorized access (security). We review how the critical system properties are handled and present a framework for their modeling. Then we present a model for the enforcement of critical system properties through situational awareness, including threat monitoring, data analysis and state prediction for decision making. We conclude by presenting a case study of a power grid simulation and advocate the ability to move from today's reactive approaches to proactive ones that aim at avoiding system failures.

 

hN. Subramanian Root Cause Analysis of Cybersecurity Incidents on Pipelines Using the NFR Approach

Abstract: Pipelines transporting oil, gas, water, and other substances form part of the critical infrastructure of the society and are mostly controlled by advanced automation technology. This automation enables remote control and monitoring of pipeline operations by means of wide area networks that include microwaves, satellites, and cellular technologies. Often these pipeline control systems are also connected to the Internet to permit their operational control from anywhere. However, this bridging of the so-called “air-gap” between the critical infrastructure control system and the Internet has also introduced cybersecurity weaknesses that allows malicious actors to take control away from legitimate users of the system. While cybersecurity needs to be built into the system during the design phase itself, it is important, especially after a cybersecurity incident, to know the actual causes behind the incident so that appropriate countermeasures may be taken quickly to avoid a recurrence of the incident. Typical techniques to identify these root causes include five whys, fishbone diagrams, and causal factors analysis; this paper presents an alternate technique to identify root causes for pipeline cybersecurity incidents based on the NFR Approach where NFR stands for Non-Functional Requirements of the pipeline system. The NFR Approach starts with the requirements for the system in the first place, establishes the relationships between the design of the system and its requirements, and then identifies the root causes in a structured manner. In this paper, the NFR Approach is applied to analyze root causes of the Florida water system attack that occurred in February 2021. The advantages of the NFR Approach over traditional methods to identify root causes especially for pipeline incidents include the traceability of the causes to the requirements of the system, identification of synergistic and conflicting operational goals, and historical record-keeping.

 

hJ. van Katwijk Digital Audio Broadcasting

Abstract: Processing digital radio - either on the transmitter or the receiver side - requires a significant amount of digital processing. A receiver for digital radio usually consists of two parts, a ”hardware” part, handling the conversion from an analog antenna signal to a stream samples, and a ”software part”, a decoder, decoding the samples and generating audio, text, images and video. In this paper some aspects of the design and implementation of Qt-DAB, a software decoder for Digital Audio Broadcasting (DAB and DAB+), is discussed. The Qt-DAB decoder runs on a variety of hardware platforms, hardware as small as creditcard sized computers as the Raspberry PI 2, and home computers. In the design performance and flexibility were key. The design is such that it is easy to interface to different hardware SDR devices and easy to add new features. While the core of the Qt-DAB software is formed by the signal processing part, interpreting the incoming sample stream and generating audio, text and images, by far the largest part of the software is handling user interaction and user comfort. Qt-DAB provides a large amount of options, options to select a device, to inspect the signal, to store signals, and options to set the configuration. All in all, it shows that about three quarters of the amount of code is involved is the non-signal processing part.

 

hM. Kłopotek, S. Wierzchoń and R. Kłopotek Weighted Laplacians of Grids and Their Application for Inspection of Spectral Graph Clustering Methods

Abstract: This paper investigates the relationship between various types of spectral clustering methods and their kinship to relaxed versions of graph cut methods. This predominantly analytical study exploits the closed (or nearly closed) form of eigenvalues and eigenvectors of unnormalized (combinatorial), normalized, and random walk Laplacians of multidimensional weighted and unweighted grids. We demonstrate that spectral methods can be compared to (normalized) graph cut clustering only if the cut is performed to minimize the sum of the weight square roots (and not the sum of weights) of the removed edges. We demonstrate also that the spectrogram of the regular grid graph can be derived from the composition of spectrograms of path graphs into which such a graph can be decomposed, only for combinatorial Laplacians. It is impossible to do so both for normalized and random-walk Laplacians. We investigate the in-the-limit behavior of combinatorial and normalized Laplacians demonstrating that the eigenvalues of both Laplacians converge to one another with an increase in the number of nodes while their eigenvectors do not. Lastly, we show that the distribution of eigenvalues is not uniform in the limit, violating a fundamental assumption of the compact spectral clustering method.

 

hR. Sanz, J. Bermejo, M. Rodríguez and E. Aguado The Role of Knowledge in Cyber-Physical Systems of Systems

Characterinsing the nature of cybephysical systems is not easy task. What are core aspects and what are not? This is especially tricky in systems-of-systems aggregates. Some EU-funded cyberphysical systems projects have performed a roadmapping exercise over the domain of Cyber-Physical Systems-of-Systems. In particlular, the EU-CPSoS project roadmap has identified three major challenges and eleven research and innovation policies that shall be addressed to solve the three challenges. The third core challenge addresses Cognitive Cyber-physical Systems of Systems. In this article we address the role that knowledge and cognition are to play in future cyber-physical systems of systems from a life-cycle perspective of high autonomy systems.

 

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