6 research outputs found

    Accountable Trapdoor Sanitizable Signatures

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    Abstract. Sanitizable signature (SS) allows a signer to partly delegate signing rights to a predeter-mined party, called sanitizer, who can later modify certain designated parts of a message originally signed by the signer and generate a new signature on the sanitized message without interacting with the signer. One of the important security requirements of sanitizable signatures is accountability, which allows the signer to prove, in case of dispute, to a third party that a message was modified by the sanitizer. Trapdoor sanitizable signature (TSS) enables a signer of a message to delegate the power of sanitization to any parties at anytime but at the expense of losing the accountability property. In this paper, we introduce the notion of accountable trapdoor sanitizable signature (ATSS) which lies between SS and TSS. As a building block for constructing ATSS, we also introduce the notion of accountable chameleon hash (ACH), which is an extension of chameleon hash (CH) and might be of independent interest. We propose a concrete construction of ACH and show how to use it to construct an ATSS scheme

    Security of Ubiquitous Computing Systems

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    The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

    Evaluating and Improving Risk Analysis Methods for Critical Systems

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    At the same time as our dependence on IT systems increases, the number of reports of problems caused by failures of critical IT systems has also increased. Today, almost every societal system or service, e.g., water supply, power supply, transportation, depends on IT systems, and failures of these systems have serious and negative effects on society. In general, public organizations are responsible for delivering these services to society. Risk analysis is an important activity for the development and operation of critical IT systems, but the increased complexity and size of critical systems put additional requirements on the effectiveness of risk analysis methods. Even if a number of methods for risk analysis of technical systems exist, the failure behavior of information systems is typically very different from mechanical systems. Therefore, risk analysis of IT systems requires different risk analysis techniques, or at least adaptations of traditional approaches. The research objective of this thesis is to improve the analysis process of risks pertaining to critical IT systems, which is addressed in the following three ways. First, by understanding current literature and practices related to risk analysis of IT systems, then by evaluating and comparing existing risk analysis methods, and by suggesting improvements in the risk analysis process and by developing new effective and efficient risk analysis methods to analyze IT systems. To understand current risk analysis methods and practices we carried out a systematic mapping study. The study found only few empirical research papers on the evaluation of existing risk analysis methods. The results of the study suggest to empirically investigate risk analysis methods for analyzing IT systems to conclude which methods are more effective than others. Then, we carried out a semi-structured interview study to investigate several factors regarding current practices and existing challenges of risk analysis and management, e.g., its importance, identification of critical resources, involvement of different stakeholders, used methods, and follow-up analysis. To evaluate and compare the effectiveness of risk analysis methods we carried out a controlled experiment. In that study, we evaluated the effectiveness of risk analysis methods by counting the number of relevant and non-relevant risks identified by the experiment participants. The difficulty level of risk analysis methods and the experiment participants’ confidence about the identified risks were also investigated. Then, we carried out a case study to evaluate the effectiveness and efficiency of existing risk analysis methods, Failure Mode and Effect Analysis (FMEA) and System Theoretic Process Analysis (STPA). The case study investigates the effectiveness of the methods by performing a comparison of how a hazard analysis is conducted for the same system. It also evaluates the analysis process of risk analysis methods by using a set of qualitative criteria, derived from the Technology Acceptance Model (TAM). After this, another case study was carried out to evaluate and assess the resilience of critical IT systems and networks by applying a simulation method. A hybrid modeling approach was used which considers the technical network, represented using graph theory, as well as the repair system, represented by a queuing model. To improve the risk analysis process, this thesis also presents a new risk analysis method, Perspective Based Risk Analysis (PBRA), that uses different perspectives while analyzing IT systems. A perspective is a point of view or a specific role adopted by risk analyst while doing risk analysis, i.e., system engineer, system tester, or system user. Based on the findings, we conclude that the use of different perspectives improves effectiveness of risk analysis process. Then, to improve the risk analysis process we carried out a data mining study to save historical information about IT incidents to be used later for risk analysis. It could be an important aid in the process of building a database of occurred IT incidents that later can be used as an input to improve the risk analysis process. Finally, based on the findings of the studies included in this thesis a list of suggestions is presented to improve the risk analysis process. This list of potential suggestions was evaluated in a focus group meeting. The suggestions are for example, risk analysis awareness and education, defining clear roles and responsibilities, easy-to-use and adapt risk analysis methods, dealing with subjectivity, carry out risk analysis as early as possible and finally using historical risk data to improve the risk analysis process. Based on the findings it can be concluded that these suggestions are important and useful for risk practitioners to improve the risk analysis process.The presented research work in this thesis provides research about methods to improve the risk analysis and management practices. Moreover, the presented work in this thesis is based on solid empirical studies

    Security of Ubiquitous Computing Systems

    Get PDF
    The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

    Next generation analytics for open pervasive display networks

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    Public displays and digital signs are becoming increasingly widely deployed as many spaces move towards becoming highly interactive and augmented environments. Market trends suggest further significant increases in the number of digital signs and both researchers and commercial entities are working on designing and developing novel uses for this technology. Given the level of investment, it is increasingly important to be able to understand the effectiveness of public displays. Current state-of-the-art analytics technology is limited in the extent to which it addresses the challenges that arise from display deployments becoming open (increasing numbers of stakeholders), networked (viewer engagement across devices and locations) and pervasive (high density of displays and sensing technology leading to potential privacy threats for viewers). In this thesis, we provide the first exploration into achieving next generation display analytics in the context of open pervasive display networks. In particular, we investigated three areas of challenge: analytics data capture, reporting and automated use of analytics data. Drawing on the increasing number of stakeholders, we conducted an extensive review of related work to identify data that can be captured by individual stakeholders of a display network, and highlighted the opportunities for gaining insights by combining datasets owned by different stakeholders. Additionally, we identified the importance of viewer-centric analytics that use traditional display-oriented analytics data combined with viewer mobility patterns to produce entirely new sets of analytics reports. We explored a range of approaches to generating viewer-centric analytics including the use of mobility models as a way to create 'synthetic analytics' - an approach that provides highly detailed analytics whilst preserving viewer privacy. We created a collection of novel viewer-centric analytics reports providing insights into how viewers experience a large network of pervasive displays including reports regarding the effectiveness of displays, the visibility of content across the display network, and the visibility of content to viewers. We further identified additional reports specific to those display networks that support the delivery of personalised content to viewers. Additionally, we highlighted the similarities between digital signage and Web analytics and introduced novel forms of digital signage analytics reports created by leveraging existing Web analytics engines. Whilst the majority of analytics systems focus solely on the capture and reporting of analytics insights, we additionally explored the automated use of analytics data. One of the challenges in open pervasive display networks is accommodating potentially competing content scheduling constraints and requirements that originate from the large number of stakeholders - in addition to contextual changes that may originate from analytics insights. To address these challenges, we designed and developed the first lottery scheduling approach for digital signage providing a means to accommodate potentially conflicting scheduling constraints, and supporting context- and event-based scheduling based on analytics data fed back into the digital sign. In order to evaluate the set of systems and approaches presented in this thesis, we conducted large-scale, long-term trials allowing us to show both the technical feasibility of the systems developed and provide insights into the accuracy and performance of different analytics capture technologies. Our work provides a set of tools and techniques for next generation digital signage analytics and lays the foundation for more general people-centric analytics that go beyond the domain of digital signs and enable unique analytical insights and understanding into how users interact across the physical and digital world
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