We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.

Transport Layer Security (TLS) is a vital component to the security ecosystem and the most popular security protocol used on the Internet today. Despite the strengths of the protocol, numerous vulnerabilities result from its improper use in practice. Some of these vulnerabilities arise from weaknesses in authentication, from the rigidity of the trusted authority system to the complexities of client certificates. Others result from the misuse of TLS by developers, who misuse complicated TLS libraries, improperly validate server certificates, employ outdated cipher suites, or deploy other features insecurely. To make matters worse, system administrators and users are powerless to fix these issues, and lack the ability to properly control how their own machines communicate securely online. In this dissertation we argue that the problems described are the result of an improper placement of security responsibilities. We show that by placing TLS services in the operating system, both new and existing applications can be automatically secured, developers can easily use TLS without intimate knowledge of security, and security settings can be controlled by administrators. This is demonstrated through three explorations that provide TLS features through the operating system. First, we describe and assess TrustBase, a service that repairs and strengthens certificate-based authentication for TLS connections. TrustBase uses traffic interception and a policy engine to provide administrators fine-tuned control over the trust decisions made by all applications on their systems. Second, we introduce and evaluate the Secure Socket API (SSA), which provides TLS as an operating system service through the native POSIX socket API. The SSA enables developers to use modern TLS securely, with as little as one line of code, and also allows custom tailoring of security settings by administrators. Finally, we further explore a modern approach to TLS client authentication, leveraging the operating system to provide a generic platform for strong authentication that supports easy deployment of client authentication features and protects user privacy. We conclude with a discussion of the reasons for the success of our efforts, and note avenues for future work that leverage the principles exhibited in this work, both in and beyond TLS.

The aim of this work is to introduce a new concept of children's home which seeks to find a relationship between family environment, specific needs of children or necessary architecture requirements which are important in perceiving the space in which children are.

A vast number of online services is based on users contributing their personal information. Examples are manifold, including social networks, electronic commerce, sharing websites, lodging platforms, and genealogy. In all cases user privacy depends on a collective trust upon all involved intermediaries, like service providers, operators, administrators or even help desk staff. A single adversarial party in the whole chain of trust voids user privacy. Even more, the number of intermediaries is ever growing. Thus, user privacy must be preserved at every time and stage, independent of the intrinsic goals any involved party. Furthermore, next to these new services, traditional offline analytic systems are replaced by online services run in large data centers. Centralized processing of electronic medical records, genomic data or other health-related information is anticipated due to advances in medical research, better analytic results based on large amounts of medical information and lowered costs. In these scenarios privacy is of utmost concern due to the large amount of personal information contained within the centralized data. We focus on the challenge of privacy-preserving processing on genomic data, specifically comparing genomic sequences. The problem that arises is how to efficiently compare private sequences of two parties while preserving confidentiality of the compared data. It follows that the privacy of the data owner must be preserved, which means that as little information as possible must be leaked to any party participating in the comparison. Leakage can happen at several points during a comparison. The secured inputs for the comparing party might leak some information about the original input, or the output might leak information about the inputs. In the latter case, results of several comparisons can be combined to infer information about the confidential input of the party under observation. Genomic sequences serve as a use-case, but the proposed solutions are more general and can be applied to the generic field of privacy-preserving comparison of sequences. The solution should be efficient such that performing a comparison yields runtimes linear in the length of the input sequences and thus producing acceptable costs for a typical use-case. To tackle the problem of efficient, privacy-preserving sequence comparisons, we propose a framework consisting of three main parts. a) The basic protocol presents an efficient sequence comparison algorithm, which transforms a sequence into a set representation, allowing to approximate distance measures over input sequences using distance measures over sets. The sets are then represented by an efficient data structure - the Bloom filter -, which allows evaluation of certain set operations without storing the actual elements of the possibly large set. This representation yields low distortion for comparing similar sequences. Operations upon the set representation are carried out using efficient, partially homomorphic cryptographic systems for data confidentiality of the inputs. The output can be adjusted to either return the actual approximated distance or the result of an in-range check of the approximated distance. b) Building upon this efficient basic protocol we introduce the first mechanism to reduce the success of inference attacks by detecting and rejecting similar queries in a privacy-preserving way. This is achieved by generating generalized commitments for inputs. This generalization is done by treating inputs as messages received from a noise channel, upon which error-correction from coding theory is applied. This way similar inputs are defined as inputs having a hamming distance of their generalized inputs below a certain predefined threshold. We present a protocol to perform a zero-knowledge proof to assess if the generalized input is indeed a generalization of the actual input. Furthermore, we generalize a very efficient inference attack on privacy-preserving sequence comparison protocols and use it to evaluate our inference-control mechanism. c) The third part of the framework lightens the computational load of the client taking part in the comparison protocol by presenting a compression mechanism for partially homomorphic cryptographic schemes. It reduces the transmission and storage overhead induced by the semantically secure homomorphic encryption schemes, as well as encryption latency. The compression is achieved by constructing an asymmetric stream cipher such that the generated ciphertext can be converted into a ciphertext of an associated homomorphic encryption scheme without revealing any information about the plaintext. This is the first compression scheme available for partially homomorphic encryption schemes. Compression of ciphertexts of fully homomorphic encryption schemes are several orders of magnitude slower at the conversion from the transmission ciphertext to the homomorphically encrypted ciphertext. Indeed our compression scheme achieves optimal conversion performance. It further allows to generate keystreams offline and thus supports offloading to trusted devices. This way transmission-, storage- and power-efficiency is improved. We give security proofs for all relevant parts of the proposed protocols and algorithms to evaluate their security. A performance evaluation of the core components demonstrates the practicability of our proposed solutions including a theoretical analysis and practical experiments to show the accuracy as well as efficiency of approximations and probabilistic algorithms. Several variations and configurations to detect similar inputs are studied during an in-depth discussion of the inference-control mechanism. A human mitochondrial genome database is used for the practical evaluation to compare genomic sequences and detect similar inputs as described by the use-case. In summary we show that it is indeed possible to construct an efficient and privacy-preserving (genomic) sequences comparison, while being able to control the amount of information that leaves the comparison. To the best of our knowledge we also contribute to the field by proposing the first efficient privacy-preserving inference detection and control mechanism, as well as the first ciphertext compression system for partially homomorphic cryptographic systems.

Current trend in automotive industry is moving towards adopting the multicore microcontrollers in Electronic Control Units (ECUs). Multicore microcontrollers give an opportunity to run a number of separated and dedicated operating systems on a single ECU. When two heterogeneous operating systems run in parallel on a multicore environment, the inter OS communication between these operating systems become the key factor in the overall performance. The inter OS communication based on shared memory is studied in this thesis work. In a setup where two operating systems namely EB Autocore OS which is based on AUTomotive Open System Architecture standard and Android are considered. Android being the gateway to the internet and due to its open nature and the increased connectivity features of a connected car, many attack surfaces are introduced to the system. As safety and security go hand in hand, the security aspects of the communication channel are taken into account. A portable prototype for multi OS communication based on shared memory communication with security considerations is developed as a plugin for EB tresos Studio.

I takt med en ökad digitalisering har det blivit ett allt större fokus på IT-säkerhet. Det finns olika typer av lösningar för att stärka IT-säkerheten och att implementera multifaktorautentisering är en av dem. I organisationers säkerhetsarbete spelar användarna en viktig roll, samtidigt kan de betraktas som ett säkerhetshot snarare än en resurs. I den här intervjustudien undersöker vi hur en implementering av multifaktorautentisering påverkar användarnas digitala arbetsmiljö. För att förstå detta har studien använt en kvalitativ datainsamlingsmetod där tio semistrukturerade intervjuer med anställda från Malmö universitet har genomförts. I analysen av resultatet har bland annat Technology Acceptance Model, Protection Motivation Theory samt ett fenomenologiskt perspektiv använts som teoretiska utgångspunkter. Studien visar att det finns en oförutsägbarhet med multifaktorautentisering som skapar en kognitiv omställning och ett hinder i arbetsflödet. Det framgår även att användarnas medvetenhet om IT-säkerhet är en viktig faktor i acceptansen av säkerhetsåtgärder så som multifaktorautentisering. Studien lyfter fram att det krävs en bra användarupplevelse bland befintliga IT-system för att välkomna och anpassa sig till framtida implementeringar av säkerhetssystem. / As digitalization has increased, there has been a growing focus on IT security. There are various types of solutions to strengthen IT security, and implementing multi-factor authentication is one of them. In the security efforts of organizations, users play an important role, but they can also be seen as a security threat rather than a resource. In this interview study, we examine how the implementation of multi-factor authentication affects users' digital work environment. To understand this, the study used a qualitative data collection method, conducting ten semi-structured interviews with employees from Malmö university. In the analysis of the results, the study utilized theoretical frameworks such as the Technology Acceptance Model, Protection Motivation Theory, and a phenomenological perspective. The study reveals that there is unpredictability associated with multi-factor authentication, creating a cognitive adjustment and a hindrance in workflow. It is also evident that users' awareness of IT security is an important factor in accepting security measures such as multi-factor authentication. The study emphasizes the need for a good user experience in existing IT systems to welcome and adapt to future implementations of security systems.

The number of secure data streams a relay-assisted interference channel can support has been an intriguing problem. The problem is not solved even for a fundamental scenario with a single antenna at each transmitter, receiver and relay. In this paper, we study the achievable secure degrees of freedom of instantaneous relay-assisted interference channels with real and complex coefficients. The study of secure degrees of freedom with complex coefficients is not a trivial multiuser extension of the scenarios with real channel coefficients as in the case for the degrees of freedom, due to secrecy constraints. We tackle this challenge by jointly designing the improper transmit signals and widely-linear relay processing strategies.

Nachhaltige und ethisch vertretbare Beschaffung und Produktion gehören zu den großen Herausforderungen, die aus dem rasanten Klimawandel und der wachsenden Weltbevölkerung resultieren. Die Erneuerbare-Energien-Richtlinie II der EU und das deutsche Lieferkettensorgfaltspflichtengesetz sind nur zwei Beispiele für die Vielzahl von Gesetzen und Vorschriften, die Standards für nachhaltige und ethisch vertretbare Beschaffung und Produktion vorgeben. Sie implizieren einen Bedarf an Transparenz, Rückverfolgbarkeit und Verifizierbarkeit von Lieferketten und Transaktionen. Öffentliche Verifikationen von Transaktionen entlang von Lieferketten ermöglichen es Dritten, die Einhaltung von Standards und Richtlinien und den Wahrheitsgehalt von Nachhaltigkeitsversprechen zu überprüfen. Folglich kann die öffentliche Überprüfbarkeit Kunden, öffentlichen Stellen und Nichtregierungsorganisationen dabei helfen, Verstöße und Betrug in Lieferketten aufzudecken. Dies wiederum kann dazu beitragen, den Druck zur Einhaltung geltender Standards und Vorschriften zu erhöhen. Transaktionen in Lieferketten basieren oft auf vertraulichen Informationen, wie beispielsweise Mengen und Preise. Die Transparenz derartiger Daten könnte auf Geschäftsgeheimnisse schließen lassen, was direkten Einfluss auf die Wettbewerbsvorteile der beteiligten Firmen hätte. Die Vereinbarkeit von Transparenz und Vertraulichkeit scheint jedoch auf den ersten Blick widersprüchlich zu sein. Diese Dissertation stellt sich der Herausforderung, die öffentliche Verifizierbarkeit von Transaktionen in Lieferketten unter Wahrung der Vertraulichkeit zu ermöglichen. Ausgehend von zwei Fallbeispielen für Lieferketten-Verifikationen werden zunächst Anforderungen an Lösungen untersucht und fünf Forschungsfragen abgeleitet. Anschließend wird eine universelle Lösung entworfen, welche Transparenz und Vertraulichkeit in Einklang bringt. Das vorgestellte Systemmodell ermöglicht sichere öffentliche Verifikationen durch den Einsatz von Fully Homomorphic Encryption (FHE) und Proxy Re-Encryption (PRE). Um die Eignung des Systemmodells für eine Vielzahl realer Szenarien zu verdeutlichen, werden in dieser Dissertation Protokolle für verschiedene Verifikationsfunktionen entworfen. Dies umfasst die Verifikation von Bilanzen, motiviert durch den Handel mit nachhaltigem Palmöl, sowie die Verifikation von Verhältnissen, veranschaulicht durch die Verarbeitung verschiedener Arten von Kobalt. Durch theoretische und empirische Untersuchungen wird nachgewiesen, dass die Protokolle sichere öffentliche Verifikationen für realitätsnahe Szenarien in praktikabler Zeit ermöglichen. Im Weiteren werden die Sicherheitseigenschaften und -implikationen des vorgeschlagenen Systemmodells und der Protokolle untersucht. Dies beinhaltet eine formale Analyse des Risikos, vertrauliche Informationen im Falle wiederholter, gleicher Verifikationen preiszugeben. Aufgrund der Anfälligkeit gegenüber derartigen Angriffen beim Verwenden probabilistischer Output Obfuscation, wird das Paradigma der Data-Dependent Deterministic Obfuscation (D3O) vorgestellt. D3O ist ein universelles Konzept und damit unabhängig vom Anwendungsfall der Lieferketten-Verifikation. Daher kann es in einer Vielzahl weiterer Protokolle für sichere Berechnungen eingesetzt werden, um das Abfließen vertraulicher Informationen zu reduzieren. / Sustainable and ethical sourcing and production are major challenges that arise from rapid climate change and our growing world population. The EU's Renewable Energy Directive II and the German Supply Chain Act are just two examples of the multitude of laws and regulations that define standards for sustainable and ethical sourcing and production. They imply a need for supply chain transparency, traceability, and verification. Public verification of supply chain transactions gives any third-party verifier the chance to evaluate compliance and the correctness of claims based on supply chain transaction details. Therefore, public verification can help customers, buyers, regulators, and non-governmental organizations uncover non-compliance and fraud committed by supply chain actors. This, in turn, can help increase the pressure to comply with applicable standards and regulations. Supply chain transactions often involve confidential data like amounts or prices. Transparency of such data could leak trade secrets and affect companies' competitive advantages. However, reconciling transparency with confidentiality seems contradictory at first glance. This thesis takes up the challenge of enabling privacy-preserving public verification of confidential supply chain transactions. Given two exemplary real-world use cases for supply chain verification, the thesis first investigates requirements for valid solutions and infers five research questions. It then designs a universal solution that combines transparency with confidentiality. The proposed system model achieves privacy-preserving public verification by employing the cryptographic techniques of fully homomorphic encryption (FHE) and proxy re-encryption (PRE). To demonstrate the suitability of the system model for a large variety of lifelike supply chain verification scenarios, the thesis designs privacy-preserving protocols for different verification functions. This includes the verification of balances, using the trade in sustainable palm oil as an example, as well as the verification of ratios, motivated by different forms of cobalt sourcing. These protocols are evaluated both theoretically and empirically. Through extensive empirical evaluation, the proposed protocols prove to enable privacy-preserving public verification for the mentioned supply chain scenarios in practical time. Additionally, this thesis investigates the security implications of the proposed system model and protocols and formally analyzes the risk of leaking information through repeated similar verifications. Based on the identified vulnerability to such attacks in the case of probabilistically obfuscated protocol outputs, the thesis introduces and investigates the paradigm of data-dependent deterministic obfuscation (D3O). D3O is a universal concept that is independent of the field of supply chain verification. It can reduce the leakage of confidential information in a large class of privacy-preserving protocols.

Lors de l’intégration en milieu de pratique clinique, les infirmières nouvellement diplômées peuvent vivre un choc de transition (Duchscher et Windey, 2018; Wakefield, 2018). Cette période d’adaptation à un nouveau rôle professionnel comprend plusieurs défis, et peut avoir un impact psychologique sur l’infirmière. Ces facteurs vont venir influencer l’expérience vécue de l’infirmière et la signification accordée à ce phénomène. L’intégration sera d’autant plus difficile dans un milieu complexe et particulier tel que l’hôpital sécuritaire surspécialisé en psychiatrie légale. Le but de cette recherche est d’explorer l’expérience vécue d’infirmières débutantes dans un hôpital sécuritaire surspécialisé de psychiatrie légale. Les questions de recherche à explorer sont en lien avec les aspects facilitateurs et les facteurs contraignants rencontrés durant leur parcours, le rôle de l'infirmière dans ce domaine, et leurs besoins d’accompagnement et de soutien en tant que débutantes. En effet, divers programmes de formation et d’orientation sont développés pour aider les infirmières à traverser cette période d’intégration. Cependant des difficultés persistent lors de l’intégration ce qui peut avoir un impact sur l’expérience vécue (Tingleff et Gildberg, 2014). Le cadre de référence théorique qui a permis de guider et structurer cette recherche est « De novice à expert », proposé par Patricia Benner (1982), et le stade de l’infirmière débutante est celui qui correspond aux infirmières nouvellement diplômées. Un devis qualitatif avec une approche phénoménologique interprétative (Benner, 1994) a été utilisé. Cinq infirmières (n=5) ont participé à une entrevue individuelle semi-dirigée d’une durée de trente à soixante minutes pour discuter de leur expérience vécue dans le milieu étudié qui a été enregistrée en audio. L’analyse qualitative des données a été effectuée de manière interprétative et itérative. De cette analyse ont émergé trois catégories principales, et dix sous-catégories. Les trois principales catégories sont : 1) les réalités du milieu clinique, ensuite 2) l’infirmière au cœur des soins en psychiatrie légale, et finalement 3) l’importance d’un accompagnement soutenu et personnalisé. Les résultats obtenus permettent une meilleure compréhension du phénomène étudié. Plusieurs recommandations ont été émises afin de mieux soutenir les infirmières débutantes durant leur parcours, plus spécifiquement concernant leurs besoins de formation afin d’être mieux préparées à intégrer leur rôle dans le milieu. / When integrating clinical practice settings, newly graduated nurses may experience transition shock (Duchscher & Windey, 2018; Wakefield, 2018). This period of adjustment to a new professional role includes several challenges and can have a psychological impact on the nurse. These factors will come to influence the nurse's lived experience and the meaning attributed to this phenomenon. Integration will be especially difficult in a complex and unique environment such as a secure hospital specializing in forensic psychiatry. The purpose of this research is to explore the lived experience of beginner nurses in a secure forensic psychiatric hospital. The research questions to be explored are related to the facilitating and constraining factors encountered during their journey, their role as a nurse in this subspecialty, and their needs for guidance and support as beginners. In fact, various training and orientation programs are developed to help nurses through this integration period, but despite this, difficulties persist which can impact the lived experience (Tingleff & Gildberg, 2014). The theoretical frame of reference that guided and structured this research is “From Novice to Expert” by Patricia Benner (1982), and the advanced beginner nurse stage is the stage that corresponds to newly graduated nurses. A qualitative design with an interpretative phenomenological approach (Benner, 1994) was used. Five nurses (n=5) participated in a semi-structured individual interview lasting thirty to sixty minutes to discuss their experience in the field of study that was audio recorded. The qualitative data analysis was performed in an interpretive and iterative manner. From this analysis emerged three main categories, and ten subcategories. The three main categories are: 1) the realities of the clinical setting, then 2) the nurse at the heart of forensic psychiatric care, and finally 3) the importance of sustained and personalized support. The results obtained allow a better understanding of the phenomenon studied. Several recommendations were issued to better support new nurses during their career, more specifically concerning their training needs in order to be better prepared to integrate their role in the environment.

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