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Nadjm-Tehrani, SiminORCID iD iconorcid.org/0000-0002-1485-0802
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Publications (10 of 118) Show all publications
Törnblom, J. & Nadjm-Tehrani, S. (2019). Formal Verification of Random Forests in Safety-Critical Applications. In: Formal Techniques for Safety-Critical Systems: . Paper presented at Sixth International Workshop on Formal Techniques for Safety-Critical Systems (FTSCS 2018), Gold Coast, Australia, 16 November, 2018 (pp. 55-71). Springer
Open this publication in new window or tab >>Formal Verification of Random Forests in Safety-Critical Applications
2019 (English)In: Formal Techniques for Safety-Critical Systems, Springer, 2019, p. 55-71Conference paper, Published paper (Refereed)
Abstract [en]

Recent advances in machine learning and artificial intelligence are now being applied in safety-critical autonomous systems where software defects may cause severe harm to humans and the environment. Design organizations in these domains are currently unable to provide convincing arguments that systems using complex software implemented using machine learning algorithms are safe and correct.

In this paper, we present an efficient method to extract equivalence classes from decision trees and random forests, and to formally verify that their input/output mappings comply with requirements. We implement the method in our tool VoRF (Verifier of Random Forests), and evaluate its scalability on two case studies found in the literature. We demonstrate that our method is practical for random forests trained on low-dimensional data with up to 25 decision trees, each with a tree depth of 20. Our work also demonstrates the limitations of the method with high-dimensional data and touches upon the trade-off between large number of trees and time taken for verification.

Place, publisher, year, edition, pages
Springer, 2019
Series
Communications in Computer and Information Science, ISSN 1865-0929 ; 008
Keywords
Machine learning, Formal verification, Random forest, Decision tree
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-154368 (URN)10.1007/978-3-030-12988-0_4 (DOI)978-3-030-12987-3 (ISBN)978-3-030-12988-0 (ISBN)
Conference
Sixth International Workshop on Formal Techniques for Safety-Critical Systems (FTSCS 2018), Gold Coast, Australia, 16 November, 2018
Funder
Wallenberg AI, Autonomous Systems and Software Program (WASP)
Available from: 2019-02-07 Created: 2019-02-07 Last updated: 2019-02-15Bibliographically approved
Almgren, M., Andersson, P., Björkman, G., Ekstedt, M., Hallberg, J., Nadjm-Tehrani, S. & Westring, E. (2019). RICS-el: Building a National Testbed for Research and Training on SCADA Security. In: Eric Luiijf, Inga Žutautaitė and Bernhard Hämmerli (Ed.), Critical Information Infrastructures Security: 13th International Conference, CRITIS 2018, Kaunas, Lithuania, September 24-26, 2018, Revised Selected Papers (pp. 219-225). Springer
Open this publication in new window or tab >>RICS-el: Building a National Testbed for Research and Training on SCADA Security
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2019 (English)In: Critical Information Infrastructures Security: 13th International Conference, CRITIS 2018, Kaunas, Lithuania, September 24-26, 2018, Revised Selected Papers / [ed] Eric Luiijf, Inga Žutautaitė and Bernhard Hämmerli, Springer, 2019, p. 219-225Chapter in book (Refereed)
Abstract [en]

Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.

Place, publisher, year, edition, pages
Springer, 2019
Series
Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 11260
Keywords
Cyber security in C(I)I systems; Modelling; Simulation Analysis and Validation approaches to C(I)IP Training for C(I)IP and effective intervention
National Category
Computer Systems
Identifiers
urn:nbn:se:liu:diva-154379 (URN)10.1007/978-3-030-05849-4_17 (DOI)9783030058487 (ISBN)9783030058494 (ISBN)9783030058494 (ISBN)
Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-02-26Bibliographically approved
Toczé, K. & Nadjm-Tehrani, S. (2018). A Taxonomy for Management and Optimization of Multiple Resources in Edge Computing. Wireless Communications & Mobile Computing, Article ID 7476201.
Open this publication in new window or tab >>A Taxonomy for Management and Optimization of Multiple Resources in Edge Computing
2018 (English)In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, article id 7476201Article, review/survey (Refereed) Published
Abstract [en]

Edge computing is promoted to meet increasing performance needs of data-driven services using computational and storage resources close to the end devices at the edge of the current network. To achieve higher performance in this new paradigm, one has to consider how to combine the efficiency of resource usage at all three layers of architecture: end devices, edge devices, and the cloud. While cloud capacity is elastically extendable, end devices and edge devices are to various degrees resource-constrained. Hence, an efficient resource management is essential to make edge computing a reality. In this work, we first present terminology and architectures to characterize current works within the field of edge computing. Then, we review a wide range of recent articles and categorize relevant aspects in terms of 4 perspectives: resource type, resource management objective, resource location, and resource use. This taxonomy and the ensuing analysis are used to identify some gaps in the existing research. Among several research gaps, we found that research is less prevalent on data, storage, and energy as a resource and less extensive towards the estimation, discovery, and sharing objectives. As for resource types, the most well-studied resources are computation and communication resources. Our analysis shows that resource management at the edge requires a deeper understanding of how methods applied at different levels and geared towards different resource types interact. Specifically, the impact of mobility and collaboration schemes requiring incentives are expected to be different in edge architectures compared to the classic cloud solutions. Finally, we find that fewer works are dedicated to the study of nonfunctional properties or to quantifying the footprint of resource management techniques, including edge-specific means of migrating data and services.

Place, publisher, year, edition, pages
WILEY-HINDAWI, 2018
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-149767 (URN)10.1155/2018/7476201 (DOI)000435850600001 ()
Note

Funding Agencies|Swedish National Graduate School in Computer Science (CUGS)

Available from: 2018-07-24 Created: 2018-07-24 Last updated: 2018-08-14
Lofwenmark, A. & Nadjm-Tehrani, S. (2018). Fault and timing analysis in critical multi-core systems: A survey with an avionics perspective. Journal of systems architecture, 87, 1-11
Open this publication in new window or tab >>Fault and timing analysis in critical multi-core systems: A survey with an avionics perspective
2018 (English)In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 87, p. 1-11Article, review/survey (Refereed) Published
Abstract [en]

With more functionality added to future safety-critical avionics systems, new platforms are required to offer the computational capacity needed. Multi-core processors offer a potential that is promising, but they also suffer from two issues that are only recently being addressed in the safety-critical contexts: lack of methods for assuring timing determinism, and higher sensitivity to permanent and transient faults due to shrinking transistor sizes. This paper reviews major contributions that assess the impact of fault tolerance on worst-case execution time of processes running on a multi-core platform. We consider the classic approach for analyzing the impact of faults in such systems, namely fault injection. The review therefore explores the area in which timing effects are studied when fault injection methods are used. We conclude that there are few works that address the intricate timing effects that appear when inter-core interferences due to simultaneous accesses of shared resources are combined with fault tolerance techniques. We assess the applicability of the methods to currently available multi-core processors used in avionics. Dark spots on the research map of the integration problem of hardware reliability and timing predictability for multi-core avionics systems are identified.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Embedded Systems
Identifiers
urn:nbn:se:liu:diva-149719 (URN)10.1016/j.sysarc.201.8.04.001 (DOI)000437078600001 ()
Note

Funding Agencies|Swedish Armed Forces; Swedish Defence Materiel Administration; Swedish Governmental Agency for Innovation Systems [NFFP6-2013-01203, NFFP7-2017-04890]

Available from: 2018-07-24 Created: 2018-07-24 Last updated: 2018-08-14
Asplund, M., Lövhall, J. & Nadjm-Tehrani, S. (2018). In-store payments using Bitcoin. In: 9th IFIP International Conference on New Technologies, Mobility and Security (NTMS): . Paper presented at 9th IFIP International Conference on New Technologies, Mobility and Security (NTMS). IEEE
Open this publication in new window or tab >>In-store payments using Bitcoin
2018 (English)In: 9th IFIP International Conference on New Technologies, Mobility and Security (NTMS), IEEE, 2018Conference paper, Published paper (Refereed)
Abstract [en]

The possibility of in-store payments would further increase the potential usefulness of cryptocurrencies. However, this would require much faster transaction verification than current solutions provide (one hour for Bitcoin) since customers are likely not prepared to wait a very long time for their purchase to be accepted by a store. We propose a solution for enabling in-store payments with waiting times in the order of a few seconds, which is still compatible with the current Bitcoin protocol. The idea is based on a payment card in combination with a protocol for ensuring that losing a card does not mean losing the money on it. We analyse the required transaction verification delay and also the potentially added risks that the solution brings compared to current systems.

Place, publisher, year, edition, pages
IEEE, 2018
Series
International Conference on New Technologies Mobility and Security, ISSN 2157-4952
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-152219 (URN)10.1109/NTMS.2018.8328738 (DOI)000448864200068 ()978-1-5386-3662-6 (ISBN)978-1-5386-3663-3 (ISBN)
Conference
9th IFIP International Conference on New Technologies, Mobility and Security (NTMS)
Note

Funding agencies: Research Centre on Resilient Information and Control Systems (RICS) - Swedish civil contingencies agency (MSB)

Available from: 2018-10-22 Created: 2018-10-22 Last updated: 2019-06-19
Lin, C.-Y., Nadjm-Tehrani, S. & Asplund, M. (2018). Timing-Based Anomaly Detection in SCADA Networks. In: Critical Information Infrastructures Security: . Paper presented at CRITIS, Lucca, Italy, 8-13 October, 2017 (pp. 48-59). Springer
Open this publication in new window or tab >>Timing-Based Anomaly Detection in SCADA Networks
2018 (English)In: Critical Information Infrastructures Security, Springer, 2018, p. 48-59Conference paper, Published paper (Refereed)
Abstract [en]

Supervisory Control and Data Acquisition (SCADA) systems that operate our critical infrastructures are subject to increased cyber attacks. Due to the use of request-response communication in polling, SCADA traffic exhibits stable and predictable communication patterns. This paper provides a timing-based anomaly detection system that uses the statistical attributes of the communication patterns. This system is validated with three datasets, one generated from real devices and two from emulated networks, and is shown to have a False Positive Rate (FPR) under 1.4%. The tests are performed in the context of three different attack scenarios, which involve valid messages so they cannot be detected by whitelisting mechanisms. The detection accuracy and timing performance are adequate for all the attack scenarios in request-response communications. With other interaction patterns (i.e. spontaneous communications), we found instead that 2 out of 3 attacks are detected.

Place, publisher, year, edition, pages
Springer, 2018
Series
Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349
Keywords
SCADA, Industrial Control System (ICS), Anomaly detection, Traffic periodicity
National Category
Computer Systems
Identifiers
urn:nbn:se:liu:diva-154394 (URN)10.1007/978-3-319-99843-5_5 (DOI)978-3-319-99842-8 (ISBN)978-3-319-99843-5 (ISBN)
Conference
CRITIS, Lucca, Italy, 8-13 October, 2017
Projects
RICS (Resilient Information and Control Systems)
Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-02-15Bibliographically approved
Lin, C.-Y. & Nadjm-Tehrani, S. (2018). Understanding IEC-60870-5-104 Traffic Patterns in SCADA Networks. In: Proceedings of the 4th ACM Workshop on Cyber-Physical System Security: . Paper presented at CPSS, Incheon, Korea, June 4, 2018 (pp. 51-60). NY, USA: ACM
Open this publication in new window or tab >>Understanding IEC-60870-5-104 Traffic Patterns in SCADA Networks
2018 (English)In: Proceedings of the 4th ACM Workshop on Cyber-Physical System Security, NY, USA: ACM , 2018, p. 51-60Conference paper, Published paper (Refereed)
Abstract [en]

The IEC-60870-5-104 (IEC-104) protocol is commonly used in Supervisory Control and Data Acquisition (SCADA) networks to operate critical infrastructures, such as power stations. As the importance of SCADA security is growing, characterization and modeling of SCADA traffic for developing defense mechanisms based on the regularity of the polling mechanism used in SCADA systems has been studied, whereas the characterization of traffic caused by non-polling mechanisms, such as spontaneous events, has not been well-studied. This paper provides a first look at how the traffic flowing between SCADA components changes over time. It proposes a method built upon Probabilistic Suffix Tree (PST) to discover the underlying timing patterns of spontaneous events. In 11 out of 14 tested data sequences, we see evidence of existence of underlying patterns. Next, the prediction capability of the approach, useful for devising anomaly detection mechanisms, is studied. While some data patterns enable an 80% prediction possibility, more work is needed to tune the method for higher accuracy.

Place, publisher, year, edition, pages
NY, USA: ACM, 2018
Series
CPSS ’18
Keywords
iec-60870-5-104, probabilistic suffix tree(pst), scada, traffic patterns
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-154412 (URN)10.1145/3198458.3198460 (DOI)000461237800008 ()978-1-4503-5755-5 (ISBN)
Conference
CPSS, Incheon, Korea, June 4, 2018
Projects
RICS (Resilient Information and Control Systems)
Note

Funding agencies: Swedish Civil Contingencies Agency (MSB)

Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-04-01Bibliographically approved
Pereira, D., Hirata, C., Pagliares, R. & Nadjm-Tehrani, S. (2017). Towards Combined Safety and Security Constraints Analysis. In: Stefano Tonetta, Erwin Schoitsch (Ed.), Proceedings of the 5th International Workshop on Assurance Cases for Software-Intensive Systems (SAFECOMP workshops): . Paper presented at ASSURE 2017: 5th International Workshop on Assurance Cases for Software-intensive Systems, Trento, Italy, September 12, 2017 (pp. 70-80). Springer, 10489
Open this publication in new window or tab >>Towards Combined Safety and Security Constraints Analysis
2017 (English)In: Proceedings of the 5th International Workshop on Assurance Cases for Software-Intensive Systems (SAFECOMP workshops) / [ed] Stefano Tonetta, Erwin Schoitsch, Springer, 2017, Vol. 10489, p. 70-80Conference paper, Published paper (Refereed)
Abstract [en]

A growing threat to the cyber-security of embedded safety-critical systems calls for a new look at the development methods for such systems. One alternative to address security and safety concerns jointly is to use the perspective of modeling using system theory. Systems-Theoretic Process Analysis (STPA) is a new hazard analysis technique based on an accident causality model. NIST SP 800-30 is a well-known framework that has been largely employed to aid in identifying threats event/source and vulnerabilities, determining the effectiveness security control, and evaluating the adverse impact of risks. Safety and security analyses, when performed independently, may generate conflicts of design constraints that result in an inconsistent design. This paper reports a novel integrated approach for safety analysis and security analysis of systems. In our approach, safety analysis is conducted with STPA while security analysis employs NIST SP800-30. It builds on a specification of security and safety constraints and outlines a scheme to automatically analyze and detect conflicts between and pairwise reinforcements of various constraints. Preliminary results show that the approach allows security and safety teams to perform a more efficient analysis.

Place, publisher, year, edition, pages
Springer, 2017
Series
Lecture Notes in Computer Science, ISSN 1611-3349
Keywords
Safety Analysis, Security Analysis, STPA, NIST SP800-30
National Category
Computer Systems
Identifiers
urn:nbn:se:liu:diva-141781 (URN)10.1007/978-3-319-66284-8_7 (DOI)2-s2.0-85029470017 (Scopus ID)
Conference
ASSURE 2017: 5th International Workshop on Assurance Cases for Software-intensive Systems, Trento, Italy, September 12, 2017
Projects
RICSNFFP6
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2018-08-14Bibliographically approved
Asplund, M. & Nadjm-Tehrani, S. (2016). Attitudes and Perceptions of IoT Security in Critical Societal Services. IEEE Access, 4, 2130-2138
Open this publication in new window or tab >>Attitudes and Perceptions of IoT Security in Critical Societal Services
2016 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 4, p. 2130-2138Article in journal (Refereed) Published
Abstract [en]

A quiet revolution that impacts several sectors, ranging over transport, home automation, energy, industrial control, and health services is undergoing with addition of new networked devices leading to enhanced services. In this paper, we aim to identify information security requirements that are common over several (vertical) sectors, and in particular, ones that impact critical societal services, namely, the energy, water, and health management systems. We present the results of an interview-based study where actors in these sectors were asked about their perceptions and attitudes on the security of Internet of Things (IoT). We set these perceptions and attitudes in context through a literature review of IoT security, and relate to current challenges in this area. This paper demonstrates that despite an overall optimistic view on IoT in critical societal services, there is a lack of consensus on risks related to IoT security.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Keywords
Internet of Things, security, risk, critical infrastructure, health
National Category
Computer Systems
Identifiers
urn:nbn:se:liu:diva-130081 (URN)10.1109/ACCESS.2016.2560919 (DOI)000377414800010 ()
Note

Funding Agencies|Vinnova; Formas; Swedish Energy Agency under IoT Strategy Program; RICS:The Research Centre on Resilient Information and Control Systems - Swedish Civil Contingencies Agency; CENIIT Project [14.04]

Available from: 2016-07-06 Created: 2016-07-06 Last updated: 2018-08-14Bibliographically approved
Vergara Alonso, E. J. & Nadjm-Tehrani, S. (2016). Fairness and Incentive Considerations in Energy Apportionment Policies. ACM Transactions on Modeling and Performance Evaluation of Computing Systems, 2(1)
Open this publication in new window or tab >>Fairness and Incentive Considerations in Energy Apportionment Policies
2016 (English)In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed) Published
Abstract [en]

The energy consumption of a system is determined by the system component usage patterns and interactions between the coexisting entities and resources. Energy accounting plays an essential role to reveal the contribution of each entity to the total consumption and for energy management. Unfortunately, energy accounting inherits the apportionment problem of accounting in general, which does not have a general single best solution. In this paper we leverage cooperative game theory commonly used in cost allocation problems to study the energy apportionment problem, i.e., the problem of prescribing the actual energy consumption of a system to the consuming entities (e.g., applications, processes or users of the system).

We identify five relevant fairness properties for energy apportionment and present a detailed categorisation and analysis of eight previously proposed energy apportionment policies from different fields in computer and communication systems. In addition, we propose two novel energy apportionment policies based on cooperative game theory which provide strong fairness notion and a rich incentive structure. Our comparative analysis in terms of the identified five fairness properties as well as information requirement and computational complexity shows that there is a trade-off between fairness and the other evaluation criteria. We provide guidelines to select an energy apportionment policy depending on the purpose of the apportionment and the characteristics of the system.

Place, publisher, year, edition, pages
ACM Digital Library, 2016
Keywords
energy apportionment, energy accounting, cooperative game theory, energy management
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-138088 (URN)10.1145/2970816 (DOI)
Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-08-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1485-0802

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