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  • 1.
    Periera, Daniel Patrick
    et al.
    ITA Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, Brazil.
    Hirata, Celso
    ITA Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, Brazil.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A STAMP-based ontology approach to support Safety and Security2019In: Journal of Information Security and Applications, ISSN 2214-2134, E-ISSN 2214-2126, Journal of Information Security and Applications Analyses, Vol. 47, p. 302-319Article in journal (Refereed)
    Abstract [en]

    Considerations of safety and security in the early stage of system life cycle are essential to collect and prioritize operation needs, determine feasibility of the desired system, and identify technology gaps. Experts from many disciplines are needed to perform the safety and security analyses, ensuring that a system has the necessary attributes. Safety assessment is usually conducted in the concept stage. On the order hand, security assessment is performed in design stage usually when an initial architecture along with the logical and physical components are defined. Systems-Theoretic Process Analysis (STPA) is a new hazard analysis technique based on systems thinking and is built on top of a new causality model of accident, which stands for Systems-Theoretic Accident Model and Processes (STAMP), grounded in systems theory. STPA for Security (STPA-Sec) is an extension of STPA that proposes to include security concerns into the analysis. STPA-Sec helps identifying some hazardous control actions, causal scenarios, and casual factors; however, no emphasis is placed on security threat scenarios. In this paper we propose an ontology-based technique that extends STPA-Sec to improve identification of causal scenarios and associated casual factors, specifically those related to security. We propose an approach that assists safety and security experts conducting safety and security analyses using STPA-Sec with a supporting ontology. First, we present an ontology representing the safety and security knowledge through STPA-Sec process, and provide a tool that implements the proposed ontology. We then propose a process to capture safety and security knowledge into the proposed ontology to identify causal scenarios. We perform a preliminary evaluation of the ontology and the process using an aeronautic case study. The results show that the ontology-based approach helps systems engineers to identify more security scenarios compared to the case where they use only STPA-Sec. Furthermore, some hazardous control actions are not addressed if the systems engineer uses the basic STPA-Sec.

  • 2.
    Pereira, Daniel Patrick
    et al.
    ITA, Brazil.
    Hirata, Celso
    ITA, Brazil.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A STAMP-based ontology approach to support safety and security analyses2019In: Journal of Information Security and Applications, ISSN 2214-2134, E-ISSN 2214-2126, Vol. 47, p. 302-319Article in journal (Refereed)
    Abstract [en]

    Considerations of safety and security in the early stage of system life cycle are essential to collect and prioritize operation needs, determine feasibility of the desired system, and identify technology gaps. Experts from many disciplines are needed to perform the safety and security analyses, ensuring that a system has the necessary attributes. Safety assessment is usually conducted in the concept stage. On the order hand, security assessment is performed in design stage usually when an initial architecture along with the logical and physical components are defined. Systems-Theoretic Process Analysis (STPA) is a new hazard analysis technique based on systems thinking and is built on top of a new causality model of accident, which stands for Systems-Theoretic Accident Model and Processes (STAMP), grounded in systems theory. STPA for Security (STPA-Sec) is an extension of STPA that proposes to include security concerns into the analysis. STPA-Sec helps identifying some hazardous control actions, causal scenarios, and casual factors; however, no emphasis is placed on security threat scenarios. In this paper we propose an ontology-based technique that extends STPA-Sec to improve identification of causal scenarios and associated casual factors, specifically those related to security. We propose an approach that assists safety and security experts conducting safety and security analyses using STPA-Sec with a supporting ontology. First, we present an ontology representing the safety and security knowledge through STPA-Sec process, and provide a tool that implements the proposed ontology. We then propose a process to capture safety and security knowledge into the proposed ontology to identify causal scenarios. We perform a preliminary evaluation of the ontology and the process using an aeronautic case study. The results show that the ontology-based approach helps systems engineers to identify more security scenarios compared to the case where they use only STPA-Sec. Furthermore, some hazardous control actions are not addressed if the systems engineer uses the basic STPA-Sec. (C) 2019 Elsevier Ltd. All rights reserved.

  • 3.
    Törnblom, John
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    An Abstraction-Refinement Approach to Formal Verification of Tree Ensembles2019In: Computer Safety, Reliability, and Security: SAFECOMP 2019 Workshops, ASSURE, DECSoS, SASSUR, STRIVE, and WAISE, Turku, Finland, September 10, 2019, Proceedings, Springer, 2019, p. 301-313Conference paper (Refereed)
    Abstract [en]

    Recent advances in machine learning are now being considered for integration in safety-critical systems such as vehicles, medical equipment and critical infrastructure. However, organizations in these domains are currently unable to provide convincing arguments that systems integrating machine learning technologies are safe to operate in their intended environments.

    In this paper, we present a formal verification method for tree ensembles that leverage an abstraction-refinement approach to counteract combinatorial explosion. We implemented the method as an extension to a tool named VoTE, and demonstrate its applicability by verifying the robustness against perturbations in random forests and gradient boosting machines in two case studies. Our abstraction-refinement based extension to VoTE improves the performance by several orders of magnitude, scaling to tree ensembles with up to 50 trees with depth 10, trained on high-dimensional data.

  • 4.
    Hirata, Celso
    et al.
    Instituto Tecnológico de Aeronáutica (ITA), Brazil.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Combining GSN and STPA for Safety Arguments2019In: Proceedings of the 7th International workshop on Assurance Cases for Software-intensive Systems (ASSURE), held in conjunction with SAFECOMP, Springer, 2019Conference paper (Refereed)
    Abstract [en]

    Dependability case, assurance case, or safety case is employed to explain why all critical hazards have been eliminated or adequately mitigated in mission-critical and safety-critical systems. Goal Structuring Notation (GSN) is the most employed graphical notation for documenting dependability cases. System Theoretic Process Analysis (STPA) is a technique, based on System Theoretic Accidents Model and Process (STAMP), to identify hazardous control actions, scenarios, and causal factors. STPA is considered a rather complex technique, but there is a growing interest in using STPA in certifications of safety-critical systems development. We investigate how STAMP and STPA can be related to use of assurance cases. This is done in a generic way by representing the STPA steps as part of the evidence and claim documentations within GSN.

  • 5.
    Törnblom, John
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Formal Verification of Random Forests in Safety-Critical Applications2019In: Formal Techniques for Safety-Critical Systems, Springer, 2019, p. 55-71Conference 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.

  • 6.
    Toczé, Klervie
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    ORCH: Distributed Orchestration Framework using Mobile Edge Devices2019In: 2019 IEEE 3RD INTERNATIONAL CONFERENCE ON FOG AND EDGE COMPUTING (ICFEC), IEEE , 2019Conference paper (Refereed)
    Abstract [en]

    In the emerging edge computing architecture, several types of devices have computational resources available. In order to make efficient use of those resources, deciding on which device a task should execute is of great importance. Existing works on task placement in edge computing focus on a resource supply side consisting of stationary devices only. In this paper, we consider the addition of mobile edge devices. We explore how mobile and stationary edge devices can augment the original task placement problem with a second placement problem: the placement of the mobile edge devices. We propose the ORCH framework in order to solve the joint problem in a distributed manner and evaluate it in the context of a spatially-changing load. Our implementation of the combined task and edge placement algorithms shows a normalized 83% delay-sensitive task completion rate compared to a perfect edge placement strategy.

  • 7.
    Bergman, Sara
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Microsoft Corporation, Oslo, Norway.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Permissioned Blockchains and Distributed Databases: A Performance Study2019In: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Concurrency and Computation, Practice and ExperienceArticle in journal (Refereed)
    Abstract [en]

    Blockchains are increasingly studied in the context of new applications. Permissioned blockchains promise to deal with the issue of complete removal of trust, a notion that is currently the hallmark of the developed society. Before the idea is adopted in contexts where resource efficiency and fast operation is a requirement, one could legitimately ask the question: can permissioned blockchains match the performance of traditional large‐scale databases? This paper compares two popular frameworks, Hyperledger Fabric and Apache Cassandra, as representatives of permissioned blockchains and distributed databases, respectively. We compare their latency for varying workloads and network sizes. The results show that, for small systems, blockchains can start to compete with traditional databases, but also that the difference in consistency models and differences in setup can have a large impact on the resulting performance.

  • 8.
    Almgren, Magnus
    et al.
    Department of computer science and engineering, Chalmers university of technology, Gothenburg.
    Andersson, Peter
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Björkman, Gunnar
    Stockholms stad / Kungliga Tekniska Högskolan, KTH, Stockholm.
    Ekstedt, Mathias
    Industrial Information and Control Systems, Royal Institute of Technology, KTH, Stockholm.
    Hallberg, Jonas
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Westring, Eric
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    RICS-el: Building a National Testbed for Research and Training on SCADA Security2019In: 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.

  • 9.
    Da Fontoura, A. A.
    et al.
    Federal University of Rio Grande do Sul, Brazil .
    Nascimento, F.A. M.
    Federal University of Rio Grande do Sul, Brazil .
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    De Freitas, E. P.
    Federal University of Rio Grande do Sul, Brazil .
    Timing Assurance of Avionic Reconfiguration Schemes using Formal Analysis2019In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, IEEE Transactions on Aerospace and Electronic Systems, E-ISSN 1557-9603Article in journal (Refereed)
    Abstract [en]

    Reconfigurable avionics systems can tolerate faults by moving functionalities from failed components to another available system component. This paper proposes a distributed reconfigurable architecture for application migration from failed modules to working ones. The feasible system reconfiguration states are determined off-line to provide the expected configuration in foreseen situations. Model Checking is used to determine feasible configurations evaluating specific temporal properties. A case study is used to show the application of the presented approach as a proof of concept

  • 10.
    Lin, Chih-Yuan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Timing Patterns and Correlations in Spontaneous SCADA Traffic for Anomaly Detection2019In: : 22nd International Symposium on Research on Attacks, Intrusions, and Defenses (RAID), USENIX - The Advanced Computing Systems Association, 2019Conference paper (Refereed)
    Abstract [en]

    Supervisory Control and Data Acquisition (SCADA) systems operate critical infrastructures in our modern society despite their vulnerability to attacks and misuse. There are several anomaly detection systems based on the cycles of polling mechanisms used in SCADA systems, but the feasibility of anomaly detection systems based on non-polling traffic, so called spontaneous events, is not well-studied. This paper presents a novel approach to modeling the timing characteristics of spontaneous events in an IEC-60870-5-104 network and exploits the model for anomaly detection. The system is tested with a dataset from a real power utility with injected timing effects from two attack scenarios. One attack causes timing anomalies due to persistent malfunctioning in the field devices, and the other generates intermittent anomalies caused by malware on the field devices, which is considered as stealthy. The detection accuracy and timing performance are promising for all the experiments with persistent anomalies. With intermittent anomalies, we found that our approach is effective for anomalies in low-volume traffic or attacks lasting over 1 hour.

  • 11.
    Toczé, Klervie
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Schmitt, Norbert
    University of Würzburg; Germany.
    Brandic, Ivona
    Vienna University of Technology, Austria.
    Aral, Atakan
    Vienna University of Technology, Austria.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Towards Edge Benchmarking: A Methodology for Characterizing Edge Workloads2019In: In Proceedings of 4th International Workshop on Foundations and Applications of Self* Systems (FAS*W),, IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    The edge computing paradigm has recently attracted research efforts coming from different application domains. However, evaluating an edge platform or algorithm is impeded by the lack of suitable benchmarks. We propose a methodology for characterizing edge workloads from different application domains. It is a first step towards defining workloads to be included in a future edge benchmarking suite. We evaluate the methodology on three use cases and find that defining a common and standard set of workloads is plausible.

  • 12.
    Souza, F. G.
    et al.
    Instituto Tecnológico de Aeronáutica, Brazil.
    Periera, Daniel Patrick
    Instituto Tecnológico de Aeronáutica, Brazil.
    Pagliares, R. M.
    Universidade Federal de Alfenas, Brazil.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Instituto Tecnológico de Aeronáutica (ITA), Brazil.
    Hirata, Celso
    Instituto Tecnológico de Aeronáutica, Brazil.
    WebSTAMP: a Web Application for STPA & STPA-Sec2019In: Proceedings of the International Cross-industry Safety Conference (ICSC) - European STAMP Workshop & Conference (ESWC) (ICSC-ESWC 2018), EDP Sciences, 2019Conference paper (Refereed)
    Abstract [en]

    STAMP (System-Theoretic Accident Model and Processes) techniques such as STPA (System- Theoretic Process Analysis) and STPA-Sec (STPA for Security) have been applied only in an adhoc manner, without the aid of tools. More recently, tools have been proposed to help the application of STPA and STPA-Sec. Most of the tools focus on user experience issues and do not cover all the aspects of STPA and STPA-Sec. Three aspects of tools are systematization, automation and analysis completeness. Systematization allows the analysis to be performed in a more disciplined way while automation allows a more time efficient analysis. Analysis’ completeness is the analysis coverage in a given domain. We identify the essential requirements supporting business and stakeholders' needs for a STAMP based tool. We propose a STAMPcompliant web application, named WebSTAMP, for STPA and STPA-Sec. WebSTAMP is intended to aid analysts throughout the analysis process in a more automated and comprehensive way, and it aims to be a collaborative tool. We illustrate how the requirements are implemented in the current version of WebSTAMP with an example of use. The results show that WebSTAMP assists analysts to conduct safety and security analyses in a more systematic, automated and comprehensive manner.

  • 13.
    Toczé, Klervie
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Taxonomy for Management and Optimization of Multiple Resources in Edge Computing2018In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, article id 7476201Article, review/survey (Refereed)
    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.

  • 14.
    Lofwenmark, Andreas
    et al.
    Saab Aeronaut, Linkoping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fault and timing analysis in critical multi-core systems: A survey with an avionics perspective2018In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 87, p. 1-11Article, review/survey (Refereed)
    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.

  • 15.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lövhall, Jakob
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    In-store payments using Bitcoin2018In: 9th IFIP International Conference on New Technologies, Mobility and Security (NTMS), IEEE, 2018Conference 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.

  • 16.
    Lin, Chih-Yuan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Timing-Based Anomaly Detection in SCADA Networks2018In: Critical Information Infrastructures Security, Springer, 2018, p. 48-59Conference 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.

  • 17.
    Lin, Chih-Yuan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Understanding IEC-60870-5-104 Traffic Patterns in SCADA Networks2018In: Proceedings of the 4th ACM Workshop on Cyber-Physical System Security, NY, USA: ACM , 2018, p. 51-60Conference 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.

  • 18.
    Boudjadar, Jalil
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Schedulability and Memory Interference Analysis of Multicore Preemptive Real-time Systems2017In: ICPE '17 Proceedings of the 8th ACM/SPEC on International Conference on Performance Engineering, ACM Press, 2017, p. 263-274Conference paper (Refereed)
    Abstract [en]

    Today's embedded systems demand increasing computingpower to accommodate the ever-growing software functionality.Automotive and avionic systems aim to leverage thehigh performance capabilities of multicore platforms, but arefaced with challenges with respect to temporal predictability.Multicore designers have achieved much progress onimprovement of memory-dependent performance in cachingsystems and shared memories in general. However, havingapplications running simultaneously and requesting the accessto the shared memories concurrently leads to interference.The performance unpredictability resulting from interferenceat any shared memory level may lead to violationof the timing properties in safety-critical real-time systems.In this paper, we introduce a formal analysis framework forthe schedulability and memory interference of multicore systemswith shared caches and DRAM. We build a multicoresystem model with a ne grained application behavior givenin terms of periodic preemptible tasks, described with explicitread and write access numbers for shared caches andDRAM. We also provide a method to analyze and recommendcandidates for task-to-core reallocation with the goalto nd schedulable congurations if a given system is notschedulable. Our model-based framework is realized usingUppaal and has been used to analyze a case study

  • 19.
    Pereira, Daniel
    et al.
    Instituto Tecnológico de Aeronáutica, São José dos Campos, Brazil.
    Hirata, Celso
    Instituto Tecnológico de Aeronáutica, São José dos Campos, Brazil.
    Pagliares, Rodrigo
    Instituto Tecnológico de Aeronáutica, São José dos Campos, Brazil.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Towards Combined Safety and Security Constraints Analysis2017In: 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 (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.

  • 20.
    Toczé, Klervie
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Where Resources meet at the Edge2017In: 2017 IEEE INTERNATIONAL CONFERENCE ON COMPUTER AND INFORMATION TECHNOLOGY (CIT), IEEE , 2017, p. 302-307Conference paper (Refereed)
    Abstract [en]

    Edge computing is a recent paradigm where network nodes are placed close to the end users, at the edge of the network. Efficient management of resources within this configuration is crucial due to scarcity and geographical spreading of edge resources. We begin by a brief description of the edge paradigm, the most generic edge architecture, and the terminology associated to it. Then, we propose and elaborate on a preliminary taxonomy for edge resource management, together with a substantial review of works in the area. Finally, we identify some research challenges.

  • 21.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Attitudes and Perceptions of IoT Security in Critical Societal Services2016In: IEEE Access, E-ISSN 2169-3536, Vol. 4, p. 2130-2138Article in journal (Refereed)
    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.

  • 22.
    Alesand, Alexander
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Vergara, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Communication Energy Evaluation for Mobile Applications: Emulating 3G over WiFi2016In: ProceedingENERGY-SIM '16 Proceedings of the 2nd International Workshop on Energy-Aware Simulation, ACM Digital Library, 2016Conference paper (Refereed)
    Abstract [en]

    Ubiquitous connectivity and massive use of mobile applications are currently hampered by fast battery drain of mobile devices. The communication energy of a mobile device is highly inuenced by the cellular operator conguration and the communication data pattern. Although testing the functionality and eciency of an application under diverse and realistic network settings is desirable, it is currently limited at the application developer test environment. It is generally hard to mimic di erent operator (infrastructure) settings that impact battery drain. In this paper we propose a system that creates a realistic cellular network testing environment for mobile applications on top of a WiFi network. A mobile device connects via WiFi to an emulator which shapes the uplink and downlink WiFi trac using real cellular operator conguration parameters. The system provides higher test repeatability compared to live networks and can be congured to emulate diverse cellular network parameters. These parameters, which determine the energy consumption, can be changed modularly and eciently. The evaluation of the resulting trac of the emulator compared to real cellular packet races from a streaming application shows a high correlation (0.97-0.98). The work has resulted in integration of the emulator within Spotify's test environment.

  • 23.
    Somarriba, Oscar
    et al.
    Electronics and Computing Department, Mondragon University, Mondragon, Spain; National University of Engineering (UNI), P.O. Box 5595, Managua, Nicaragua .
    Zurutuza, Urko
    Electronics and Computing Department, Mondragon University, Mondragon, Spain.
    Uribeetxeberria, Roberto
    Electronics and Computing Department, Mondragon University, Mondragon, Spain.
    Delosierés, Laurent
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Detection and Visualization of Android Malware Behavior2016In: Journal of Electrical and Computer Engineering, ISSN 2090-0147, Vol. 2016, article id 8034967Article in journal (Refereed)
    Abstract [en]

    Malware analysts still need to manually inspect malware samples that are considered suspicious by heuristic rules. They dissect software pieces and look for malware evidence in the code. The increasing number of malicious applications targeting Android devices raises the demand for analyzing them to find where the malcode is triggered when user interacts with them. In this paper a framework to monitor and visualize Android applications’ anomalous function calls is described. Our approach includes platform-independent application instrumentation, introducing hooks in order to trace restricted API functions used at runtime of the application. These function calls are collected at a central server where the application behavior filtering and a visualization take place. This can help Android malware analysts in visually inspecting what the application under study does, easily identifying such malicious functions.

  • 24.
    Udd, Robert
    et al.
    Sectra AB, Linköping, Sweden.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kazemtabrizi, Mehrdad
    The Royal Institute of Technology, Stockholm, Sweden.
    Ekstedt, Mathias
    The Royal Institute of Technology, Stockholm, Sweden.
    Exploiting Bro for Intrusion Detection in a SCADA System2016In: Proceedings of the 2nd ACM International Workshop on Cyber-Physical System Security, ACM Digital Library, 2016, p. 44-51Conference paper (Refereed)
    Abstract [en]

    Supervisory control and data acquisition (SCADA) systemsthat run our critical infrastructure are increasingly run withInternet-based protocols and devices for remote monitoring.The embedded nature of the components involved, and thelegacy aspects makes adding new security mechanisms in anefficient manner far from trivial. In this paper we studyan anomaly detection based approach that enables detect-ing zero-day malicious threats and benign malconfigurationsand mishaps. The approach builds on an existing platform(Bro) that lends itself to modular addition of new proto-col parsers and event handling mechanisms. As an examplewe have shown an application of the technique to the IEC-60870-5-104 protocol and tested the anomaly detector withmixed results. The detection accuracy and false positiverate, as well as real-time response was adequate for 3 ofour 4 created attacks. We also discovered some additionalwork that needs to be done to an existing protocol parser toextend its reach.

  • 25.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fairness and Incentive Considerations in Energy Apportionment Policies2016In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed)
    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.

  • 26.
    Vergara, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fairness and Incentive Considerations in Energy Apportionment Policies2016In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed)
    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 in revealing 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 article, we leverage cooperative game theory, which is commonly used in cost allocation problems to study the energy apportionment problem, that is, 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 that 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 tradeoff 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.

  • 27.
    Toczé, Klervie
    et al.
    Ericsson AB, Linköping, Sweden.
    Vasilevskaya, Maria
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sandahl, Patrik
    Ericsson AB, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Maintainability of Functional Reactive Programs in a Telecom Server Software2016In: SAC '16 Proceedings of the 31st Annual ACM Symposium on Applied Computing, Association for Computing Machinery (ACM), 2016, p. 2001-2003Conference paper (Other academic)
    Abstract [en]

    Functional Reactive Programming (FRP) is claimed to be a good choice for event handling applications. Current object- oriented telecom applications are known to suffer from additional complexity due to event handling code. In this paper we study the maintainability of FRP programs in the tele- com domain compared to traditional object-oriented programming (OOP), with the motivation that higher maintainability increases the service quality and decreases the costs. Two implementations of the same procedure are created: one using Haskell and the reactive-banana FRP frame- work and one using C++ and the OOP paradigm. Four software experts each with over 20 years of experience and three development engineers working on a product subject to study were engaged in evaluations, based on a questionnaire involving five different aspects of maintainability. The evaluations indicate a higher maintainability profile for FRP compared with OOP. This is confirmed by a more detailed analysis of the code size. While performance was not a main criteria, a preliminary evaluation shows that the OOP prototype is 8-10 times faster than the FRP prototype in the current (non-optimised) implementations.

  • 28.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Model-based Security Risk Analysis for Networked Embedded Systems2016In: Critical Information Infrastructures Security: 9th International Conference, CRITIS 2014 Limassol, Cyprus, October 13–15, 2014 Revised Selected Papers / [ed] Panayiotou C., Ellinas G., Kyriakides E., Polycarpou M., Springer, 2016, p. 381-386Conference paper (Refereed)
    Abstract [en]

    Finding a balance between functional and non-functional requirements and resources in embedded systems has always been a challenge. What brings this challenge into a sharper focus is that embedded devices are increasingly deployed in many networked applications, some of which will form the backbone of the critical information infrastructures on which we all depend. The Security-Enhanced Embedded system Development (SEED) process has proposed a set of tools that a bridge the two islands of expertise, the engineers specialised in embedded systems development and the security experts. This paper identifies a gap in the tool chain that links the identification of assets to be protected to the associated security risks seen from different stakeholder perspectives. The needed tool support for systematic prioritisation of identified assets, and the selection of security building blocks at design stage based on a risk picture of different stakeholders, are characterised. The ideas are illustrated in a smart metering infrastructure scenario.

  • 29.
    Boudjadar, Jalil
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Hyun Kin, Jin
    University of Pennsylvania, USA.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Performance-aware Scheduling of Multicore Time-critical Systems2016In: / [ed] IEEE, IEEE, 2016, p. 105-114Conference paper (Refereed)
    Abstract [en]

    Despite attractiveness of multicore processors for embedded systems, the potential performance gains need to be studied in the context of real-time task scheduling and memory interference. This paper explores performance-aware schedula-bility of multicore systems by evaluating the performance when changing scheduling policies (as design parameters). The modelbased framework we build enables analyzing the performance of multicore time-critical systems using processor-centric and memory-centric scheduling policies. The system architecture we consider consists of a set of cores with a local cache and sharing the cache level L2 and main memory (DRAM). The metrics we use to compare the performance achieved by different configurations of a system are: 1) utilization of the cores; and 2) the maximum delay per access request to shared cache and DRAM. Our framework, realized using UPPAAL, can be viewed as an engineering tool to be used during design stages to identify the scheduling policies that provide better performance for a given system while maintaining system schedulability. As a proof of concept, we analyze and compare 2 different cases studies.

  • 30.
    Kalns, Gundars
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Vasilevskaya, Maria
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Trading off Latency against Security in Open Energy Metering Infrastructures2016In: Proceedings of The 4th International Symposium for Industrial Control Systems and SCADA Cyber Security (ICS-CSR), British Computer Society (BCS), 2016Conference paper (Refereed)
    Abstract [en]

    Embedded devices are expected to transform the landscape of networked services in many domains, among them smart homes and smart grid systems. The reliable and optimised operation of smart grids is dependent on reliable data provided by end nodes (e.g. smart meters), and assurance of secure communication across networks. Understanding whether advanced security building blocks have a role to play in forthcoming infrastructures needs a basic understanding of each potential building block with respect to resource usage and impact on timing. In this paper we study the performance penalty of asymmetric cryptography techniques used for protection of wirelessly transmitted data in a prototype smart metering system. The prototype system is built using hardware and software components from “Open Energy Monitor” project using a wireless data link between the metering device and the data collector device. We investigate the use of the Elliptic Curve Integrated Encryption Scheme (ECIES) in two versions - with standard building blocks and with added Elliptic Curve Digital Signature Algorithm (ECDSA) support. The use of the ECDSA allows the system to achieve the non-repudiation property. We compare those cryptographic techniques with the Advanced Encryption Standard in Galois Counter Mode (AES-GCM) technique in two versions - with 128 bit and 256 bit keys. Performance is compared in terms of execution time of (1) preparing data, (2) unpacking it, and (3) roundtrip time. We then discuss the implications of the measurements, where the roundtrip time of sending one measurement ranges from 378 ms in case of AES128-GCM to 16.3 sec using ECIES with ECDSA.

  • 31.
    Löfwenmark, Andreas
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Saab Aeronautics.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Understanding Shared Memory Bank Access Interference in Multi-Core Avionics2016Conference paper (Refereed)
    Abstract [en]

    Deployment of multi-core platforms in safety-critical applications requires reliable estimation of worst-case response time (WCRT) for critical processes. Determination of WCRT needs to accurately estimate and measure the interferences arising from multiple processes and multiple cores. Earlier works have proposed frameworks in which CPU, shared cache, and shared memory (DRAM) interferences can be estimated using some application and platform-dependent parameters. In this work we examine a recent work in which single core equivalent (SCE) worst case execution time is used as a basis for deriving WCRT. We describe the specific requirements in an avionics context including the sharing of memory banks by multiple processes on multiple cores, and adapt the SCE framework to account for them. We present the needed adaptations to a real-time operating system to enforce the requirements, and present a methodology for validating the theoretical WCRT through measurements on the resulting platform. The work reveals that the framework indeed creates a (pessimistic) bound on the WCRT. It also discloses that the maximum interference for memory accesses does not arise when all cores share the same memory bank.

  • 32.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Communication Energy Overhead of Mobiles Games2015In: MobiGames '15: Proceedings of the 2nd Workshop on Mobile Gaming, Association for Computing Machinery (ACM), 2015, p. 1-6Conference paper (Other academic)
    Abstract [en]

    Although a significant proportion of the mobile apps are games there has been little attention paid to their specific characteristics with respect to communication energy. In this paper we select 20 mobile games among the top 100 free Android games, and study their data patterns and communication energy use over a total of 25 hours of playing. The analysis of the energy for communication over 3G networks indicates that there is a wide variation among the games, the largest footprint being 8 times higher than the lowest one. The results also indicates both app-specific and category-specific relations between data pattern and energy use, as well as variations in CPU utilisation.

  • 33.
    Löfwenmark, Andreas
    et al.
    Saab Aeronautics, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Experience Report: Memory Accesses for Avionic Applications and Operating Systems on a Multi-core Platform2015In: 2015 IEEE 26TH INTERNATIONAL SYMPOSIUM ON SOFTWARE RELIABILITY ENGINEERING (ISSRE), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 153-160Conference paper (Refereed)
    Abstract [en]

    The deployment of multi-core platforms in safety-critical avionic applications is hampered by the lack of means to ensure predictability when processes running on different cores can create interference effects, affecting worst-case execution time, due to shared memory accesses. One way to restrict these interferences is to allocate a budget for different processes prior to run-time and to monitor the adherence to this budget during run-time. While earlier works in adopting this approach seem promising, they focus on application level (user mode) accesses to shared memory and not the operating system accesses. In this paper we construct experiments for studying a multi-core platform running an ARINC 653 compliant operating system, and measure the impact of both application processes and operating system (supervisor mode) activities. In particular, as opposed to earlier works that considered networking applications, we select four avionic processes that exhibit different memory access patterns, namely, a navigation process, a matrix multiplication process, a math library process and an image processing one. The benchmarking on a set of avionic-relevant application processes shows that (a) the potential interference by the operating system cannot be neglected when allocating budgets that are to be monitored at run-time, and (b) the bounds for the allowed number of memory accesses should not always be based on the maximum measured count during profiling, which would lead to overly pessimistic budgets.

  • 34.
    Bernardo, Vitor
    et al.
    Department of Informatics Engineering, University of Coimbra, Coimbra, Portugal.
    Braun, Torsten
    University of Bern, Bern, Switzerland.
    Curado, Marilia
    Department of Informatics Engineering, University of Coimbra, Coimbra, Portugal.
    Fiedler, Markus
    Blekinge Institute of Technology, Karlskrona, Sweden.
    Hock, David
    University of Würzburg, Würzburg, Germany.
    Hossmann, Theus
    ETH Zurich, Zurich, Switzerland.
    Hummel, Karin Anna
    ETH Zurich, Zurich, Switzerland.
    Hurni, Philipp
    University of Bern, Bern, Switzerland.
    Ickin, Selim
    Blekinge Institute of Technology, Karlskrona, Sweden.
    Jamakovic-Kapic, Almerima
    University of Bern, Bern, Switzerland.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Trinh, Tuan Ahn
    Budapest University of Technology and Economics, Budapest, Hungary.
    Vergara, Ekhiotz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Wamser, Florian
    University of Würzburg, Würzburg, Germany.
    Zinner, Thomas
    University of Würzburg, Würzburg, Germany.
    Green wireless-energy efficiency in wireless networks2015In: Large-scale distributed systems and energy efficiency: A holistic view, John Wiley & Sons, 2015Chapter in book (Refereed)
    Abstract [en]

    Wireless networks have become more and more popular because of ease of installation, ease of access, and support of smart terminals and gadgets on the move. In the overall life cycle of providing green wireless technology, from production to operation and, finally, removal, this chapter focuses on the operation phase and summarizes insights in energy consumption of major technologies. The chapter also focuses on the edge of the network, comprising network access points (APs) and mobile user devices. It discusses particularities of most important wireless networking technologies: wireless access networks including 3G/LTE and wireless mesh networks (WMNs); wireless sensor networks (WSNs); and ad-hoc and opportunistic networks. Concerning energy efficiency, the chapter discusses challenges in access, wireless sensor, and ad-hoc and opportunistic networks.

  • 35.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Quantifying Risks to Data Assets Using Formal Metrics in Embedded System Design2015In: Computer Safety, Reliability, and Security: 34th International Conference, SAFECOMP 2015, Delft, The Netherlands, September 23-25, 2015, Proceedings / [ed] Floor Koornneef; Coen van Gulijk, Springer, 2015, Vol. 9337, p. 347-361Conference paper (Refereed)
    Abstract [en]

    This paper addresses quantifying security risks associated with data assets within design models of embedded systems. Attack and system behaviours are modelled as time-dependent stochastic processes. The presence of the time dimension allows accounting for dynamic aspects of potential attacks and a system: the probability of a success- ful attack changes as time progresses; and a system possesses different data assets as its execution unfolds. These models are used to quan- tify two important attributes of security: confidentiality and integrity. In particular, likelihood/consequence-based measures of confidentiality and integrity losses are proposed to characterise security risks to data assets. In our method, we consider attack and system behaviours as two sepa- rate models that are later elegantly combined for security analysis. This promotes knowledge reuse and avoids adding extra complexity in the system design process. We demonstrate the effectiveness of the proposed method and metrics on smart metering devices. 

  • 36.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Rapid selection and dissemination of urgent messages over delay-tolerant networks (DTNs)2015In: Advances in Delay-Tolerant Networks (DTNs): Architecture and Enhanced Performance / [ed] J. Rodrigues, Elsevier, 2015, p. 187-203Chapter in book (Refereed)
    Abstract [en]

    Today many new applications are emerging that take advantage of wireless communication in handheld and embedded devices. Some of these emerging applications, such as information sharing in vehicular systems, have strong requirements for timely message dissemination, even if the network is not always 100% connected. In this chapter we discuss message differentiation mechanisms that can be used in intermittently connected networks to improve delivery and latency properties when messages have a limited time to live in the network. We present a simulation-based study on a large-scale vehicular scenario comparing different prioritisation mechanisms for a partition-tolerant manycast protocol. We show that negative effects of overloads can be significantly reduced by using information within the message about how far it has spread and how much time is remaining.

  • 37.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sharing the Cost of Lunch: Energy Apportionment Policies2015In: Proceedings of the 11th ACM Symposium on QoS and Security for Wireless and Mobile Networks, ACM Digital Library, 2015, p. 91-97Conference paper (Refereed)
    Abstract [en]

    Energy consumption has become a hot topic in computer and communication technologies pinpointing the need to carefully analyse system efficiency. The energy consumption of a system is determined by the usage patterns of system components and complex interactions between the coexisting entities and resources. Providing transparency of a system’s consumption by breaking down the total consumption is vital to evaluate and provide energy-efficient design and operation.

    In this paper we survey the apportionment problem in different fields such as computer systems, wireless sensor networks, mobile devices and energy-efficient buildings. The challenge lies in how to attribute a share of the total energy consumption to the responsible entities (e.g., applications, processes or users of the system). Our analysis identifies that energy apportionment is a common problem in different fields and reviews five previously applied energy apportionment policies. Also, the work identifies relevant further research.

  • 38.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Support for Cross-domain Composition of Embedded Systems Using MARTE Models2015In: ACM SIGBED Review, ISSN 1551-3688, p. 37-45Article in journal (Refereed)
    Abstract [en]

    Abstract—Embedded systems have evolved from tailormade systems developed by specialist engineers to artefacts built from complex software/hardware components with many extra-functional concerns. Ubiquity of embedded devices demands other facets such as security and safety to be brought to the fore- front. At the same time, cost efficiency dictates building systems from reusable building blocks. However, integration of extra- functional building blocks comes with a certain performance resource overhead that must be taken into consideration while designing resource-constraint embedded systems. This paper builds on the premise that functional models can be extended with platform modelling to help the application engineers to select the right extra-functional building blocks accounting for performance implications of their integration. We define a UML profile relating it to relevant parts of the MARTE profile in order to capture the performance analysis results for a reusable building block, and a generic notion of model-based compatibility analysis for platform models. Additionally, our approach rests on creation of ontologies to store MARTE description of hardware components, and is supported by a MagicDraw plugin developed for capturing the analysis results and performing the compatibility analysis.

  • 39.
    Löfwenmark, Andreas
    et al.
    Saab Aeronaut, Avion Equipment, Linkoping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Challenges in Future Avionic Systems on Multi-core Platforms2014In: 2014 IEEE International Symposium on Software Reliability Engineering Workshops, IEEE, 2014, p. 115-119Conference paper (Refereed)
    Abstract [en]

    Modern avionic system development is undergoing a major transition, from federated systems to Integrated Modular Avionics (IMA) where several applications with mixed criticality will reside on the same platform. Moreover, there is a departure from today’s single core computing, and we need to address the problem of how to guarantee determinism (in time and space) for application tasks running on multiple cores and interacting through shared memory. This paper summarizes the main challenges and briefly describes some active directions in research regarding temporal partitioning. It also outlines the forthcoming research that we will pursue for quantifying time bounds on memory access related interference, to ensure determinism and comply with certification requirements.

  • 40.
    Bianzino, Aruna Prem
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Cooperative proxies: Optimally trading energy and quality of service in mobile devices2014In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 75, no Part A, p. 297-312Article in journal (Refereed)
    Abstract [en]

    This work studies the energy and quality of service (QoS) trade-off in the context of mobile devices with two communication interfaces (a high energy and a low energy interface). We propose an optimisation scheme during underload scenarios where proxy groups are dynamically formed exploiting both interfaces. The scheme integrates a reward mechanism that compensates a proxy while carrying other group members’ traffic, and deals with churn (joining and leaving of nodes) in a cell area. For traffic flows that approximate knowledge about current services we show that the scheme can achieve energy savings of 60% for all mobile nodes as whole. We also demonstrate the impact on disruption-sensitive flows as a function of the traffic mix, and that the use of rewards for selection of proxies is a fair mechanism in the long term.

  • 41.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Prihodko, Mihails
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    EnergyBox: Disclosing the wireless transmission energy cost for mobile devices2014In: Sustainable Computing: Informatics and Systems, ISSN 2210-5379, Vol. 4, no 2, p. 118-135Article in journal (Refereed)
    Abstract [en]

    While evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions still hamper the quality of experience to a great extent. The energy consumption of data transmission is highly dependent on the traffic pattern, and we argue that designing energy efficient data transmissions starts by energy awareness. Our work proposes EnergyBox, a parametrised tool that facilitates accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end using real traffic data.

    The tool takes as input the parameters of a network operator and the power draw for a given mobile device in the 3G and WiFi transmission states. It outputs an estimate of the consumed energy for a given packet trace, either synthetic or captured in a device using real applications. Using nine different applications with different data patterns the versatility and accuracy of the tool was evaluated. The evaluation was carried out for a modern and popular smartphone in the WiFi setting, a specific mobile broadband module for the 3G setting, and within the operating environment of a major mobile operator in Sweden. A comparison with real power traces indicates that EnergyBox is a valuable tool for repeatable and convenient studies. It exhibits an accuracy of 94–99% for 3G, and 95–99% for WiFi given the studied applications’ traces.

    Next the tool was deployed in a use case where a location sharing application was ran on top of two alternative application layer protocols (HTTP and MQTT) and with two different data exchange formats (JSON and Base64). The illustrative use case helped to identify the appropriateness of the pull and push strategies in sharing location data, and the benefit of EnergyBox in characterising where the breaking point lies for preferring one or the other protocol, under which network load, or exchange data format.

  • 42.
    Lundberg, Jonas
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Törnqvist, Eva
    Linköping University, The Tema Institute, Technology and Social Change. Linköping University, Faculty of Arts and Sciences.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Establishing conversation spaces in hastily formed networks: the worst fire in modern Swedish history2014In: Disasters. The Journal of Disaster Studies, Policy and Management, ISSN 0361-3666, E-ISSN 1467-7717, Vol. 38, no 4, p. 790-807Article in journal (Refereed)
    Abstract [en]

    In presenting examples from the most extensive and demanding fire in modern Swedish history, this paper describes challenges facing hastily formed networks in exceptional situations. Two concepts that have been used in the analysis of the socio-technical systems that make up a response are conversation space and sensemaking. This paper argues that a framework designed to promote understanding of the sensemaking process must take into consideration the time at which as well as the location in which an individual is engaged in an event. In hastily formed networks, location is partly mediated through physical systems that form conversation spaces of players and their interaction practices. This paper identifies and discusses four challenges to the formation of shared conversation spaces. It is based on the case study of the 2006 Bodträskfors forest fire in Sweden and draws on the experiences of organised volunteers and firefighters who participated in a hastily formed network created to combat the fire. 

  • 43.
    Vasilevskaya, Maria
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Software and Systems.
    Ariani Gunawan, Linda
    Norwegian University of Science and Technology, NTNU.
    Nadjm-Tehrani, Simin
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Software and Systems.
    Herrmann, Peter
    Norwegian University of Science and Technology, NTNU.
    Integrating security mechanisms into embedded systems by domain-specific modelling2014In: Security and Communication Networks, ISSN 1939-0114, E-ISSN 1939-0122, Vol. 7, no 12, p. 2815-2832Article in journal (Refereed)
    Abstract [en]

    Embedded devices are crucial enablers of the Internet of Things and become increasingly common in our daily life. They store, manipulate and transmit sensitive information and, therefore, must be protected against security threats. Due to the security and also resource constraint concerns, designing secure networked embedded systems is a difficult task. Model-based development (MBD) is promoted to address complexity and ease the design of software intensive systems. We leverage MBD and domain-specific modelling to characterise common issues related to security and embedded systems that are specific to a given application domain. Security-specific knowledge relevant for a certain application domain is represented in the form of an adapted information security ontology. Further, the elements of the ontology are associated with security building blocks modelled with the MBD method SPACE. The selection of relevant security building blocks is based on (i) assets automatically elicited from the functional models, (ii) domain security knowledge captured by the security expert and (iii) the platform adopted by the embedded system engineer. A tool is developed to support the steps supporting this methodology and help to bridge between the security and embedded systems domains. We illustrate our approach with a case study from the smart metering domain.

  • 44.
    Santos, Javier
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Prem Bianzino, Aruna
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Monkey Gamer: Automatic profiling of Android games2014In: International Conference on Mobile Computing, Applications and Services (MobiCASE), IEEE conference proceedings, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Creation of smartphone applications has undergone a massive explosion in recent years and there is an urgent need for evaluation of their resource efficiency, trustworthiness and reliability. A large proportion of these apps are going to be within the gaming area. In this paper we classify game apps on the basis of their development process, their I/O process and their interaction level. We present Monkey Gamer, a software to automatically play a large class of Android games and collect execution traces, based on a state machine to partially describe the game structure and interactions. A significant similarity is shown when comparing the results obtained by the Monkey Gamer and by human players, for three of the most popular Android games. We evaluate the performance of the Monkey Gamer by comparing the traces it generates with traces created when humans play the games, and find significant similarity in the trace sets.

  • 45.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Andersson, Simon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    When Mice Consume Like Elephants: Instant Messaging Applications2014In: e-Energy '14: Proceedings of the 5th international conference on Future energy systems, ACM Press, 2014, p. 97-107Conference paper (Refereed)
    Abstract [en]

    A recent surge in the usage of instant messaging (IM) applications on mobile devices has brought the energy efficiency of these applications into focus of attention. Although IM applications are changing the message communication landscape, this work illustrates that the current versions of IM applications differ vastly in energy consumption when using the third generation (3G) cellular communication. This paper shows the interdependency between energy consumption and IM data patterns in this context. We analyse the user interaction pattern using a IM dataset, consisting of 1043370 messages collected from 51 mobile users. Based on the usage characteristics, we propose a message bundling technique that aggregates consecutive messages over time, reducing the energy consumption with a trade-off against latency. The results show that message bundling can save up to 43% in energy consumption while still maintaining the conversation function. Finally, the energy cost of a common functionality used in IM applications that informs that the user is currently typing a response, so called typing notification, is evaluated showing an energy increase ranging from 40-104%.

  • 46.
    Raciti, Massimiliano
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Embedded Cyber-Physical Anomaly Detection in Smart Meters2013Conference paper (Other academic)
    Abstract [en]

    Smart grid security has many facets, ranging over a spectrum from resisting attacks aimed at supervisory and control systems, to end user privacy concerns while monitored by the utility enterprise. This multi-faceted problem also includes vulnerabilities that arise from deployment of local cyber-physical attacks at a smart metering location, with a potential to a) manipulate the measured energy consumption, and b) being massively deployed aiming at destabilisation. In this paper we study a smart metering device that uses a trusted platform for storage and communication of metering data, and show that despite the hard core security, there is still room for deployment of a second level of defence as an embedded real-time anomaly detector that can cover both the cyber and physical domains.

  • 47.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    EnergyBox: A Trace-driven Tool for Data Transmission Energy Consumption Studies2013In: EE-LSDS 2013, Energy Efficiency in Large Scale Distributed Systems, Springer, 2013, p. 19-34Conference paper (Refereed)
    Abstract [en]

    Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. We argue that the design of energy-efficient solutions starts by energy-awareness and propose EnergyBox, a tool that provides accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end. We recognize that the energy consumption of data transmission is highly dependable on the traffic pattern, and provide the means for trace-based iterative packet-driven simulation to derive the operation states of wireless interfaces. The strength of EnergyBox is that it allows to modularly set the 3G network parameters specified at operator level, the adaptive power save mode mechanism for a WiFi device, and the different power levels of the operation states for different handheld devices. EnergyBox enables efficient energy consumption studies using real data, which complements the device-dependent laborious physical power measurements. Using real application transmission traces, we have validated EnergyBox showing an accuracy range of 94-99% for 3G and 93-99% for WiFi compared to the real measured energy consumption by a 3G modem and a smartphone with WiFi.

  • 48.
    Sandulescu, Gabriel
    et al.
    University of Luxembourg .
    Schaffer, Peter
    University of Luxembourg .
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Exploiting resource heterogeneity in delay-tolerant networks2013In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 13, no 3, p. 230-243Article in journal (Refereed)
    Abstract [en]

    Routing in delay and disruption-tolerant networks (DTNs) relies on intermediary nodes, called custodians, to deliver messages to destination. However, nodes usually differ significantly in terms of available resources: energy, buffer space and bandwidth. Routing algorithms need to make the most efficient use of custodian resources while also making sure those in limited supply are not exhausted. This paper proposes a distributed scheme for calculating resources available in node vicinity as a tool to support meaningful routing decisions. A generic model is developed first and is then applied to individual network assets. The model is based on a sparse network, where resources are potentially not uniformly distributed. It uses recent encounters to estimate resource availability in node vicinity. It is shown that a store-carry-forward scheme may benefit from accessing vicinity resource estimates. This knowledge allows nodes to implement meaningful custodian election and queue management strategies, approached here from a holistic perspective. It is demonstrated that routing protocols not only use up fewer resources overall but also consume resources preferentially from nodes with higher resource levels, sparing nodes with limited supplies. As a result, disparities in available resources across the node population are significantly reduced, and nodes are less likely to leave the network as a consequence of resource depletion.

  • 49.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Sanjuan, Joseba
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kernel Level Energy-Efficient 3G Background Traffic Shaper for Android Smartphones2013Conference paper (Refereed)
    Abstract [en]

    Reducing the energy consumption of wireless devices is paramount to a wide spread adoption of mobile applications. Cellular communication imposes high energy consumption on the mobile devices due to the radio resource allocation, which differs from other networks such as WiFi. Most applications are unaware of the energy consumption characteristics of third generation cellular communication (3G). This makes the background small data transfers of undisciplined applications an energy burden due to inefficient utilisation of resources.

    While several approaches exist to reduce the energy consumption of this best-effort background traffic by means of traffic shaping, we find that they are mostly evaluated with simulations and the actual energy overhead for the traffic shaper itself has not been studied. In order to cover this gap, our work realises an existing energy saving algorithm as a Kernel Level Shaper (KLS) within the Android platform, and measures its energy footprint. The total energy savings of our implementation range from 8% to 58% for emulated real background traffic, that is categorised as best-effort traffic. We further show the implications of running the KLS during live operation of applications as an exploratory study.

  • 50.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Prihodko, Mihails
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Mobile Location Sharing: An Energy Consumption Study2013In: e-Energy '13 Proceedings of the 4th International Conference on Future Energy Systems: Where Energy, Computing and Communication Meet, New York, NY, USA: ACM Press, 2013, p. 289-290Conference paper (Refereed)
    Abstract [en]

    The use of a mobile device's battery for frequent transmissions of position data in a location sharing application can be more expensive than the location retrieval itself. This is in part due to energy-agnostic application development and in part dependent on choice of protocols. This paper studies the lightweight Message Queuing Telemetry Transport protocol (MQTT) as an application layer protocol on top of the third generation cellular communication. The energy efficiency and amount of data generated by the publish/subscribe MQTT protocol is experimentally compared against the Hypertext Transfer Protocol (HTTP), which is currently used in typical location sharing applications.

    The evaluation results indicate that MQTT is a good candidate as a protocol for location sharing. At comparable bandwidth and energy expenses MQTT offers better quality of user experience, since the subscribers are notified at once when the location of some interesting client has changed. Our measurements show that MQTT is more energy-efficient than HTTP in the idle state and when the number of other users with whom the client shares location is low. When the number of users increases beyond 3, HTTP becomes the preferred option in terms of energy efficiency at the cost of a higher notification delay.

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