Safety and Security of Cyber-Physical Systems: Engineering dependable Software using Principle-based Development

559 Pages·2022·10.081 MB·English

by  Frank J. Furrer

Frank J. Furrer
Safety and Security
of Cyber-Physical
Systems
Engineering dependable Software using
Principle-based Development
Safety and Security of Cyber-Physical Systems
Frank J. Furrer
Safety and Security of
Cyber-Physical Systems
Engineering dependable Software using
Principle-based Development
Frank J. Furrer
Computer Science Faculty
Technical University of Dresden
Dresden, Germany
ISBN 978-3-658-37181-4 ISBN 978-3-658-37182-1 (eBook)
https://doi.org/10.1007/978-3-658-37182-1
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Fachmedien Wiesbaden
GmbH, part of Springer Nature 2022
This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether
the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse
of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and
transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or
dissimilar methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does
not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective
laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this book
are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the
editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors
or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Responsible Editor: Leonardo Milla
This Springer Vieweg imprint is published by the registered company Springer Fachmedien Wiesbaden GmbH,
part of Springer Nature.
The registered company address is: Abraham-Lincoln-Str. 46, 65189 Wiesbaden, Germany
Foreword
This book is about cyber-physical systems. A Google search for this term results in
405’000’000 hits in 0.64 seconds (25.01.2022). Together with the strongly linked use of
the term and the concept with other related popular terms such as Industry 4.0 and (IoT)
Internet of Things, this fact clearly shows the importance of cyber-physical systems in
the present and the upcoming world!
The NIST characterization: “Cyber-Physical Systems (CPS) comprise interacting dig-
ital, analog, physical, and human components engineered for function through integrated
physics and logic. These systems will provide the foundation of our critical infrastruc-
ture, form the basis of emerging and future smart services, and improve our quality of
life in many areas. Cyber-physical systems will bring advances in personalized health
care, emergency response, traffic flow management, and many more” (https://www.nist.
gov/el/cyber-physical-systems, [Last accessed: 16.06.2021]).
Suffices by itself to underline the importance of the field.
This characterization does not explicitly mention the correct operation and continuous
availability of cyber-physical systems and is apparently taken for granted. However, we
need and somehow expect such fundamental properties to become a “commodity” for
the functioning of our modern CPS-based society.
Unfortunately, reaching this goal will require a lot of effort, research, and practice. In
fact, all existing cyber-physical systems are and will ever be under the continuous influ-
ence of cyber-attacks, faults, and failures hitting their software or underlying hardware,
possibly causing unavailability or improper behavior of their operating environment,
human errors, or being impacted by malicious activities.
This book precisely addresses those challenges that are at the basis of proper func-
tioning of cyber-physical systems and the infrastructures they compose: It deals with the
focused and fundamental issue of engineering principles for safety and security.
The book is divided into two main parts, each providing significant contributions
toward managing safety and security.
The first addresses all the relevant concepts and explains their relations and links to
the reader. Here the book offers many definitions and provides the conceptual framework
for cyber-physical systems. All the facets of CPSs and the possible safety and security
v
vi Foreword
implications are linked to the fundamental notion of risk. Finally, all the impairments
to proper functioning at all possible locations are explored and exemplified so that the
reader can have a comprehensive view of the complexity that needs to be managed
appropriately.
While the first part provides and structures the essential knowledge on safety, secu-
rity, and risk, the second part elaborates on proper responses regarding a few paramount
questions that must be asked: 1) How are good safety and security defined? 2) How is
good safety and security formalized? 3) How is good safety and security taught? 4) How
is good safety and security enforced?
This book provides enlightening solutions by defining, formalizing, strictly applying,
and enforcing safety and security principles. In fact, good safety and security principles
provide reliable knowledge for the successful architecting of trustworthy cyber-physical
systems.
The second part of the book introduces and then details the concept of principle-
based engineering to explain and justify a number of safety and security principles. This
approach to architecting safe and secure systems is complemented and enriched by many
instructive examples and practical observations, which add value to the book and allow
the message to arrive clearly and sound.
I also want to remark the high value of the book as an instrument for teaching and
education. Given its style and the richness of the examples made, the book can be used
both as a textbook for graduate students but also as a guideline for the practitioner and
the engineer as a help for a correct application of the safety and security principles when
architecting and implementing cyber-physical systems of any of the types and variations
described in the book.
The reader will appreciate how the book grew out of the long-running activities of the
author and shows the admirable maturity he has achieved, both in the vastity of the mate-
rial included and the presentation style. All this makes the book a source of inspiration.
I wish the readers to enjoy reading this rewarding book as I had!
June 2021 Prof. Dr. Andrea Bondavalli
Head of the Resilient Computing Lab
Department of Mathematics and Informatics
University of Florence, Italy
I-50134 - Firenze, Italy
Preface
Today, Cyber-Physical Systems (CPS) are at the core of our industrial society. We rely
heavily on cyber-physical systems in all areas of work and life.
Cyber-physical systems combine a cyber-part, i.e., a software-controlled computer
system, with a physical part, i.e., a real system. The software operates the physical sys-
tem. Examples of cyber-physical systems are cars, airplanes, trains, communications and
energy infrastructures, heart pacemakers, medical diagnosis equipment, water treatment
plants, and many more.
Controlling a physical system by software has tremendous benefits: It allows nearly
unlimited functionality, high flexibility for extensions and changes, and cost-effective
implementations. Because of these benefits, a large, capable, and profitable software
industry has evolved.
However, cyber-physical systems introduce a new danger: Because they directly
affect the real, physical world, they have the potential to cause harm, injury, or loss to
the users of the CPS. A cyber-physical system's failure, malfunction, or unavailability
may have grave consequences, such as accidents, loss of life, damage to property or the
environment, or severe legal repercussions. A CPS's trustworthiness is the most crucial
factor for its safe use and acceptance by its users. It is, therefore, the critical responsibil-
ity of the CPS industry to build, maintain, and evolve trustworthy cyber-physical systems
(TwCPS).
Unfortunately, all cyber-physical systems today cannot operate undisturbed: They are
under the continuous influence of negative factors, such as cyber-attacks, faults, and fail-
ures in their software or underlying hardware, unavailability or dysfunction of their oper-
ating environment, human errors, or malicious activities. Therefore, the task of creating a
trustworthy CPS is a considerable one!
Because of a CPS’s possibility to generate harm, the concept of risk and risk manage-
ment becomes central. All sources of negative impact on and within the CPS must be
methodically, ultimately, and competently identified, assessed, mitigated, and reduced to
an acceptable residual risk. Therefore, the science of “dealing with risks” is the founda-
tion of a trustworthy CPS.
vii
viii Preface
Trustworthiness is a CPS property: It is an umbrella term that heads a taxonomy of
constituent properties. The most important are safety and security, embedded in a legal
framework. This monograph focuses exclusively on safety and security.
Safety and security are properties of the complete CPS, i.e., including the hardware,
networks, systems and communications software, application software, the operat-
ing environment, and the users. This monograph's focus is additionally narrowed to the
application software, i.e., the software providing the control functionality of the CPS.
This monograph is not a “cookbook” for creating and evolving safe and secure CPS’s.
The objective is to provide fundamental engineering principles which are proven and
powerful for building trustworthy cyber-physical systems.
Quote
“I would advise students to pay more attention to the fundamental ideas rather
than the latest technology. The technology will be out-of-date before they graduate.
Fundamental ideas never get out-of-date”
David L. Parnas, 2001 (in [Hoffman01])
The literature contains thousands of principles and patterns applicable to safe and secure
applications software for CPSs—here, the most general and influential are chosen.
Wherever necessary, the monograph points specifically to valuable literature that delves
deeper into a specific subject matter—this is the reason for the extensive list of references.
A note on terminology: Unfortunately, the formidable knowledge available in the ref-
erences uses a lot of unprecise and even conflicting terminology. This monograph, there-
fore, precisely defines all terms used—as part of the conceptual integrity.
This “guidebook” addresses safety and security teams in the CPS industry, as well as
software engineers, both in practice and during university education. It is also well suited
to a one-semester, graduate-level lecture at Technical universities.
This monograph relies on and has some overlap with the author’s previous book:
“Future-Proof Software-Systems—A Sustainable Evolution Strategy”, Springer Vieweg-
Verlag, 2019, ISBN 978-3-658-19937-1 ([Furrer19]). Some parts are reused here.
A final observation: This book contains hundreds of principles on more than 600
pages. Which do we apply to a specific project or product? The answer is: risk analysis!
The risk analysis identifies the threats, the possible failure modes, uncovers the vulner-
abilities, specifies the mitigation measures, and estimates the acceptable residual risks.
The required risk mitigation measures to reach acceptable residual risk dictate the
applicable principles. No more, no less!
Stein am Rhein (Switzerland) Frank J. Furrer
in June 2022
Acknowledgments
A book is never the achievement of one person. This book grew out of my lectures as
Honorary Professor at the faculty of Computer Science at the Technical University of
Dresden (Germany), which started in the winter term of 2013/2014. Special thanks go
to the chair of the software technology, Prof. Dr. Uwe Aßmann, for his continued sup-
port. In addition, my numerous students contributed to the quality of the content and the
didactic flow by their active participation during the lectures and their valuable engage-
ment in my seminars.
I repeat my sincere thanks to Stephan Murer and Bruno Bonati, who started me on
this journey ([Murer11], [Furrer19]).
A book is never the achievement of one author: He stands on the shoulders of
giants—of which the extensive reference section for each chapter of the book is proof.
Authoring an English-language book for a German-native speaker is not a sim-
ple task. I would like to acknowledge the invaluable help from the language checker
“Grammarly” (https://www.grammarly.com).
Finally, I wish to express my gratitude to Springer-Verlag for the extensive sup-
port during the creation of this monograph and especially to my editors Sybille Thelen,
David Imgrund, Leonardo Milla, Heike Jung, and the copy-editor Roopashree Polepalli
for their highly valuable assistance. They all made the publication process a successful
pleasure.
Finally, thanks go to you—my reader—for investing your valuable time reading this
book.
Frank J. Furrer
[email protected]
ix
Contents
Part I Foundation
1 Introduction .................................................... 3
1.1 Cyber-Physical Systems ..................................... 3
1.2 Risk in Cyber-Physical Systems .............................. 5
References ...................................................... 7
2 Cyber-Physical Systems .......................................... 9
2.1 Cyber-Physical Systems ..................................... 9
2.2 Cyber-Physical Systems-of-Systems ........................... 12
2.3 Emergence ............................................... 14
2.4 Infrastructure ............................................. 17
2.4.1 Introduction ...................................... 17
2.4.2 ICS Architecture ................................... 18
2.5 Autonomous Cyber-Physical Systems .......................... 21
2.6 Internet of Things .......................................... 22
2.7 Cloud-Based Cyber-Physical Systems .......................... 23
2.7.1 Conceptual Architecture ............................. 23
2.7.2 Cloud Safety, Security, and Real Time ................. 27
2.8 Token Economy ........................................... 29
2.9 Cyber-crime and Cyber-war .................................. 31
2.9.1 Cyber-crime ...................................... 32
2.9.2 Cyber-war ........................................ 35
2.10 Diffuse Computer Crime .................................... 39
2.10.1 Supply Chain Dangers .............................. 39
2.10.2 Insider Crime ..................................... 41
2.11 Cyber-Physical Systems Engineering .......................... 42
2.11.1 Safety- and Security-Aware Development Process ........ 42
2.11.2 Governance ...................................... 45
2.11.3 Competence Center ................................ 46
xi