La sécurité des communications sans fil omniprésentes devient, ces dernières années, de plus en plus une exigence incontournable. Bien que la cryptographie symétrique assure largement la confidentialité des données, la difficulté concerne la génération et la distribution de clés secrètes. Récemment, des études indiquent que les caractéristiques inhérentes du canal de propagation peuvent être exploitées afin de consolider la sécurité. En particulier, le canal radio fournit en effet une source d'aléa commune à deux utilisateurs à partir de laquelle des clés secrètes peuvent être générées. Dans la présente dissertation, nous nous intéressons au processus de génération de clés secrètes (SKG), tout en reliant les propriétés du canal radio à la qualité des clés générées. D'abord nous développons un modèle du canal stochastique, traitant la sécurité du point de vue de l'espion, qui montre une mémoire de canal résiduelle bien au-delà d'une distance de quelques longueurs d'onde (scénarios spatialement non-stationnaires). Ensuite, nous exploitons les degrés de liberté (DOF) du canal et analysons leur impact sur la performance de SKG dans différentes conditions, tout en considérant des canaux plus réalistes en environnements extérieur et intérieur (respectivement grâce à des données déterministes simulées et à des mesures). Les résultats montrent que, même pour des bandes modérées (comme standardisées dans la norme IEEE 802.11), le seul DoF de fréquence ou de son association avec le DoF spatial est souvent suffisant pour générer des longues clés, à condition d'utiliser une méthode efficace de quantification des coefficients complexes du canal. / Nowadays, the security of ubiquitous wireless communications becomes more and more a crucial requirement. Even though data is widely protected via symmetric ciphering keys, a well-known difficulty is the generation and distribution of such keys. In the recent years therefore, a set of works have addressed the exploitation of inherent characteristics of the fading propagation channel for security. In particular, secret keys could be generated from the wireless channel, considered as a shared source of randomness, available merely to a pair of communicating entities. ln the present dissertation, we are interested in the approach of secret key generation (SKG) from wireless channels, especially in relating the radio channel properties to the generated keys quality. We first develop a stochastic channel model, focusing on the security with respect to the eavesdropper side, which shows a residual channel memory weil beyond a few wavelengths distance (spatially nonstationary scenarios). Then, we analyze the channel degrees of freedom (DoF) and their impact on the SKG performance in different channel conditions, especially by considering more realistic channels in both outdoor and indoor environments (respectively through simulated ray tracing data and through measurements). The results show that, even for moderately wide band (such as standardized in IEEE 802.11), the sole frequency DOF or its association with the spatial DOF is often enough for generating long keys, provided an efficient quantization method of the complex channel coefficients is used.

The United States Supreme Court decision in the Roe v. Wade (1973) case provides women with a right to privacy and the liberty to make decisions concerning their reproductive lives. With this, women who become pregnant are offered the right to choose between keeping their pregnancy and terminating the pregnancy by way of abortion. Since Roe v. Wade (1973), many women have exercised their reproductive liberties, as evidenced by the termination of over 60 million pregnancies via legal abortion in the United States. Still, secrecy among women with a history of abortion remains a common phenomenon. Studies conducted on abortion and reasons for abortion are innumerable and literature on reasons women keep abortion secret are readily available. However, research lacks in the area of examining the lived experience of women with history of abortion secret. Thus, this research examines this phenomenon from women’s lived experiences and the effects of the secret on their relationship(s) when kept from at least one person(s) with whom the post-abortive women are/were in relationship. Purposive sampling was used to select five female participants for this study. To examine participants’ lived experience with abortion secret history as it relates to its effects on relationship(s), the researcher employed qualitative method Interpretative Phenomenological Analysis (IPA) in conjunction with Bowen Family Systems Theory approach. Seven superordinate themes emerged from the data analysis: self-sacrifice, emotional aftermath of abortion secret; secrecy as protection; dance of anxiety; effects on relationships; generational experiences; and, finding freedom. The collaborative use of IPA and Family Systems Theory provided an understanding of participants’ experiences, the effects of the secret on participants, as well as their emotional systems. The data collected added to the limited research available on this phenomenon providing space for post-abortive women’s secrecy experience to be heard.

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The fourth generation cellular mobile broadband, Long-Term Evolution (LTE), provides high speed Internet via Internet Protocol (IP). Today’s wireless infrastructure paves the way to a connected society where high speed Internet is seamlessly available at all times for anyone to use. To achieve this, a mobile service subscriber can no longer be bound to a single network provided by a single operator. Thus, roaming constitutes a key pillar in shaping the connected society Local Breakout (LBO) Voice over Long-Term Evolution (VoLTE) roaming enables a mobile service subscriber to breakout from its home network, and to use network services in a visited network. LBO requires control signalling and user data to be routed over several Public Land Mobile Networks (PLMNs), thus making mobile service subscriber’s the subject of Lawful Intercept (LI) across multiple networks. This thesis project investigates the possibility of using Multimedia Internet KEYing (MIKEY) and Secure Real-Time Transport Protocol (SRTP) to encrypt the payload of VoLTE media packets. More specifically, a Law Enforcement Monitoring Provider (LEMP) is designed, implemented, and evaluated. LEMP is deployed within a cell phone and serves to distribute cryptographic key shares to Trusted Third Parties (TTPs), i.e. multiple escrow agents, entrusted to store these cryptographic key shares. The result preserves the requirements for LI despite the fact that there may be multiple network operators involved. Moreover, the experiments show that the distribution time depends primarily on network latency rather than the time required to split the cryptographic key in chunks; hence the approach is usable in practice. / Den fjärde generationens mobila bredband, Long-Term Evolution (LTE), möjliggör användandet av höghastighetsinternet över Internet Protocol (IP). Dagens trådlösa infrastrukturer banar väg för ett fritt och lättillgängligt digitalt samhälle där alla kan vara uppkopplade samtidigt. För att uppnå global trådlös infrastruktur måste mobilabonnenten ha möjlighet att utnyttja flera andra trådlösa nätverk än det nätverk som teleoperatören binder dem till. Därför utgör fri roaming en viktig del i utvecklingen av framtidens globala trådlösa infrastrukturer. Local Breakout (LBO) Voice over Long-Term Evolution (VoLTE) är en roamingarkitektur som gör det möjligt för en mobilabonnent att kopplas upp från en teleoperatörs nät till en annans. LBO kräver att kontrollsignaler och användardata skickas mellan flera operatörer innan trafiken når sitt mål, och därmed utsätts mobilabonnenten för laglig avlyssning av elektronisk information på flera platser samtidigt. Det här examensarbetet undersöker möjligheten att använda Multimedia Internet KEYing (MIKEY) och Secure Real-Time Transport Protocol (SRTP) för att kryptera mediatrafik i VoLTE. Under arbetets gång utvecklas och utvärderas en Law Enforcement Monitoring Provider (LEMP). LEMP är placerad i en mobiltelefon och distribuerar delar av krypteringsnycklar till flera betrodda tredje parter (till flera escrow agents). Detta gör det möjligt att uppfylla kraven för laglig avlyssning av elektronisk information även när flera teleoperatörer avlyssnar användardata och kontrollsignaler. Resultatet visar att distribueringstiden primärt beror på nätverkslatens, och inte på den tid det tar att fördela krypteringsnyckeln i mindre delar. Därför kan den här metoden användas i praktiken.

<p>Secure computation allows mutually distrusting parties to compute over private data. Such collaborations have widespread applications in social, scientific, commercial, and security domains. However, the overhead of achieving security is a major bottleneck to the adoption of such technologies. In this context, this thesis aims to design the most secure protocol within budgeted computational or network resources by mathematically formulating it as an optimization problem. </p> <p>With the rise in CPU power and cheap RAM, the offline-online model for secure computation has become the prominent model for real-world security systems. This thesis investigates the above-mentioned optimization problem in the information-theoretic offline-online model. In particular, this thesis presents the following selected sample of our research in greater detail. </p> <p>Round and Communication Complexity: Chor-Kushilevitz-Beaver characterized the round and communication complexity of secure two-party computation. Since then, the case of functions with randomized output remained unexplored. We proved the decidability of determining these complexities. Next, if such a protocol exists, we construct the optimal protocol; otherwise, we present an obstruction to achieving security. </p> <p>Rate and Capacity of secure computation: The efficiency of converting the offline samples into secure computation during the online phase is essential. However, investigating this ``production rate'' for general secure computations seems analytically intractable. Towards this objective, we introduce a new model of secure computation -- one without any communication -- that has several practical applications. We lay the mathematical foundations of formulating rate and capacity questions in this framework. Our research identifies the first tight rate and capacity results (a la Shannon) in secure computation. </p> <p>Reverse multiplication embedding: We identify a new problem in algebraic complexity theory that unifies several efficiency objectives in cryptography. Reverse multiplication embedding seeks to implement as many (base field) multiplications as possible using one extension field multiplication. We present optimal construction using algebraic function fields. This embedding has subsequently led to efficient improvement of secure computation, homomorphic encryption, proof systems, and leakage-resilient cryptography. </p> <p>Characterizing the robustness to side-channel attacks: Side-channel attacks present a significant threat to the offline phase. We introduce the cryptographic analog of common information to characterize the offline phase's robustness quantitatively. We build a framework for security and attack analysis. In the context of robust threshold cryptography, we present a state-of-the-art attack, threat assessment, and security fix for Shamir's secret-sharing. </p> <p><br></p>

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En av de viktigaste delarna i bostadsaffärer är budgivningen, både för mäklare, säljare och köpare. Budgivningen är dock inte reglerad i lag och bud är inte bindande. Säljaren bestämmer över budgivningen och spekulanterna bestämmer över sina bud. Mäklarens hantering av budgivningen är reglerad genom lag och praxis, bland annat skyldigheten att tillvarata båda parters intressen. Med dessa utgångspunkter kan budgivningen i vissa fall bli problematisk, något som har uppmärksammats i samband med dolda bud. Ett dolt bud innebär att det endast gäller under förutsättning att det inte kommuniceras till övriga spekulanter. Det har blivit allt vanligare på bostadsmarknaden men det saknas information och fördjupning inom ämnet. Därav är syftet med denna uppsats att studera dolda bud och vilka effekter det har på förmedlingsprocessen utifrån en kvalitativ forskningsmetod med induktiv ansats. Studien utgörs i huvudsak av intervjuer med olika erfarna personer inom bostadsmarknaden i Stockholm, men utreder även vad dolda bud innebär och hur det förhåller sig till regler, lagar och praxis.  Det finns en stor problematik kring dolda bud och det innebär en risk för alla inblandade parter. Budgivningen brister i transparens och det är inte ovanligt att det leder till besvikelse och frustration. Det förekommer i samband med att marknaden är het och leder till en snabb affär där alla inte får chans att delta i budgivningen som många har att förlora på. Marknaden sätter inte priset vilket leder till slutpriser som mer eller mindre skiljer sig från marknadsvärdet. Ekonomiskt sett är det i princip alltid någon av parterna som förlorar på affären, antingen betalar köparen för mycket eller så får säljaren mindre än vad man hade kunnat få i en öppen budgivning. Framför allt är det övriga spekulanter som blir upprörda för att de inte har fått möjlighet att delta i budgivningen och det är oftast mäklaren som får kritiken. Okunskap och orättvisa är orsaken till missnöjet och problematiken som uppstår på bostadsmarknaden. Mäklare samt branschexperter ser detta som ett allt vanligare problem och det leder till ett dåligt rykte för bostadsmarknaden, särskilt för mäklarna. Branschens ambition är att bostadsaffärer ska vara tydliga och informativa för alla parter med en öppen och transparent budgivning. / One of the most vital parts in real estate business is the bidding process, for both the broker, seller and the buyer. Although, the bidding process is not regulated by the law and the bids are not binding. The seller is deciding over the bidding process and the potential buyers are in charge of their offerings. How the realtor is handling the bidding process is regulated by law and by praxis, for example the obligation to include the interest of both parties (seller and potential buyer). Based on these premises, the bidding process can in some cases become problematic, which have been highlighted in association of sealed bids. A sealed bid involves a condition that it will last only if it is not communicated to other speculators. This phenomenon become more common on the real estate market, although it lacks information and knowledge within this topic. Therefore, the purpose of this bachelor thesis is to study sealed bids and identify what effects it has on the brokerage process, based on a qualitative study method with an inductive approach. The study is mainly based on interviews with different people with different experiences within the sector of real estate in Stockholm. In addition, it also investigates what sealed bids means and how it is related to rules, laws and praxis.  There is a huge issue with sealed bids and it involves a risk for all parties involved. The bidding process is lacking in transparency and it is likely that it generates disappointment and frustration. It occurs in association when the market is blooming, which generates quick deals where not everyone get the chance to participate in the process of bidding. The market does not set the price, which leads to selling prices that differs from the market value. From a financial point of view, one of the parties usually losing out in the deal, with either the buyer paying too much, or the seller receiving less than what they could have received in an open bidding process. Overall, the other speculators get upset due to that they have not been getting the opportunity to participate in the bidding and it is often the realtor who receives the criticism. Lack of knowledge and injustice are the reasons of the dissatisfaction and the problem that arises on the real estate market. Brokers and other experts within the sector see this as a more common issue and it gives the real estate market a bad reputation, especially for the brokers. The ambition of the sector is that the real estate deals should be more direct and informative for all parties involved with an open and transparent bidding process.

No / The Versatile and Ubiquitous Secret Sharing System, a cloud data repository secure access and a web based authentication scheme. It is designed to implement the sharing, distribution and reconstruction of sensitive secret data that could compromise the functioning of an organisation, if leaked to unauthorised persons. This is carried out in a secure web environment, globally. It is a threshold secret sharing scheme, designed to extend the human trust security perimeter. The system could be adapted to serve as a cloud data repository and secure data communication scheme. A secret sharing scheme is a method by which a dealer distributes shares of a secret data to trustees, such that only authorised subsets of the trustees can reconstruct the secret. This paper gives a brief summary of the layout and functions of a 15-page secure server-based website prototype; the main focus of a PhD research effort titled ‘Cryptography and Computer Communications Security: Extending the Human Security Perimeter through a Web of Trust’. The prototype, which has been successfully tested, has globalised the distribution and reconstruction processes. / Petroleum Technology Development Fund

Работа посвящена осмыслению и комплексному описанию когнитивных признаков, смыслового объема и способов репрезентации концепта «Тайна» в русской языковой картине мира. Материал исследования составили: 190 лексических единиц со значением тайны в толковании слова, извлеченных из толковых, фразеологических, семантических, синонимических и антонимических словарей русского языка; 590 расширенных контекстов, представленных в Национальном корпусе русского языка; 149 ассоциатов, полученных в результате психолингвистического эксперимента. В первой главе работы рассматриваются теоретические принципы и концептуальная база исследования, раскрываются ключевые понятия «языковая картина мира», «концепт» и «концептосфера», а также описываются методики концептуального анализа и ассоциативного эксперимента. Во второй главе рассматриваются семантическая структура концепта «Тайна», его когнитивные признаки и смысловой объем концепта. Проводится анализ дискурсивного варьирования лексем, являющихся базовыми репрезентантами концепта «Тайна», на основе данных, собранных в Национальном корпусе русского языка. После этого производится проверка семантического содержания исследуемого концепта на основе результатов, полученных в ходе проведения цепочечного ассоциативного эксперимента. Материалы исследования могут быть использованы в преподавании дисциплин гуманитарного профиля («Когнитивная лингвистика», «Лингвокультурология»), а также при создании учебных пособий, словарей концептов или лингвокультурных тезаурусов. В приложении представлена иллюстрация структуры концепта «Тайна». / The thesis is devoted to the understanding and comprehensive description of cognitive features, semantic scope and ways of representing the concept of “taina” (“secret”) in the Russian linguistic picture of the world. The research material consisted of 190 lexical units with the meaning of secret in the meaning of the word, extracted from explanatory, phraseological, semantic, synonymic and antonymic dictionaries of the Russian language; 590 extended contexts presented in the National Corpus of the Russian Language; 149 associates obtained during a psycholinguistic experiment. The first chapter of the thesis examines the theoretical principles and conceptual framework of the research. It reveals the key concepts of “linguistic picture of the world”, “concept” and “conceptual sphere”, and describes the methods of conceptual analysis and associative experiment. The second chapter examines the semantic structure of the concept of “Secret”, its cognitive features and the semantic scope of the concept. The analysis of the discursive variation of lexemes, which are the basic representatives of the concept of “Secret”, is carried out on the basis of data collected in the National Corpus of the Russian Language. The semantic content of the concept is checked based on the results obtained during the associative chain experiment. The research materials can be used in teaching humanities disciplines (“Cognitive Linguistics”, “Linguoculturology”), as well as in creating textbooks, conceptual dictionaries or linguistic and cultural thesauruses. The appendix provides an illustration of the structure of the concept of “Secret”.