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Internet-of-Things (IoT) devices are increasing in popularity due to their ability to help automate many aspects of daily life while performing these necessary duties on billions of low-power appliances. However, the perks of these small devices also come with additional constraints to security. Security always has been an issue with the rise of cryptographic backdoors and hackers reverse engineering the security protocols within devices to reveal the original state that was encrypted. Security researchers have done much work to prevent attacks with high power algorithms, such as the international effort to develop the current Advanced Encryption Standard (AES). Unfortunately, IoT devices do not typically have the computational resources to implement high-power algorithms such as AES, and must rely on lightweight primitives such as pseudorandom number generators, or PRNGs.This thesis explores the effectiveness, functionality, and use of PRNGs in different applications. First, this thesis investigates the confidentiality of a single-stage residue number system PRNG, which has previously been shown to provide extremely high quality outputs for simulation and digital communication applications when evaluated through traditional techniques like the battery of statistical tests used in the NIST Random Number Generation and DIEHARD test suites or in using Shannon entropy metrics. In contrast, rather than blindly performing statistical analyses on the outputs of the single-stage RNS PRNG, this thesis provides both white box and black box analyses that facilitate reverse engineering of the underlying RNS number generation algorithm to obtain the residues, or equivalently the key, of the RNS algorithm. This thesis develops and demonstrate a conditional entropy analysis that permits extraction of the key given a priori knowledge of state transitions as well as reverse engineering of the RNS PRNG algorithm and parameters (but not the key) in problems where the multiplicative RNS characteristic is too large to obtain a priori state transitions. This thesis then discusses multiple defenses and perturbations for the RNS system that defeat the original attack algorithm, including deliberate noise injection and code hopping. We present a modification to the algorithm that accounts for deliberate noise, but rapidly increases the search space and complexity. Lastly, a comparison of memory requirements and time required for the attacker and defender to maintain these defenses is presented. The next application of PRNGs is in building a translation for binary PRNGs to non-binary uses like card shuffling in a casino. This thesis explores a shuffler algorithm that utilizes RNS in Fisher-Yates shuffles, and that calls for inputs from any PRNG. Entropy is lost through this algorithm by the use of PRNG in lieu of TRNG and by its RNS component: a surjective mapping from a large domain of size $2^J$ to a substantially smaller set of arbitrary size $n$. Previous research on the specific RNS mapping process had developed a lower bound on the Shannon entropy loss from such a mapping, but this bound eliminates the mixed-radix component of the original formulation. This thesis calculates a more precise formula which takes into account the radix, $n$. This formulation is later used to specify the optimal parameters to simulate the shuffler with different test PRNGs. After implementing the shuffler with PRNGs with varying output entropies, the thesis examines the output value frequencies to discuss if utilizing PRNG is a feasible alternative for casinos to the higher-cost TRNG. / Master of Science / Cryptography, or the encrypting of data, has drawn widespread interest for years, initially sparking public concern through headlines and dramatized reenactments of hackers targeting security protocols. Previous cryptographic research commonly focused on developing the quickest, most secure ways to encrypt information on high-power computers. However, as wireless low-power devices such as smart home, security sensors, and learning thermostats gain popularity in ordinary life, interest is rising in protecting information being sent between devices that don't necessarily have the power and capabilities as those in a government facility. Lightweight primitives, the algorithms used to encrypt information between low-power devices, are one solution to this concern, though they are more susceptible to attackers who wish to reverse engineer the encrypting process. The pesudorandom number generator (PRNG) is a type of lightweight primitive that generates numbers that are essentially random even though it is possible to determine the input value, or seed, from the resulting output values. This thesis explores the effectiveness and functionality of PRNGs in different applications. First, this thesis explores a PRNG that has passed many statistical tests to prove its output values are random enough for certain applications. This project analyzes the quality of this PRNG through a new lens: its resistance to reverse engineering attacks. The thesis describes and implements an attack on the PRNG that allows an individual to reverse engineer the initial seed. The thesis then changes perspective from attacker to designer and develop defenses to this attack: by slightly modifying the algorithm, the designer can ensure that the reverse engineering process is so complex, time-consuming, and memory-requiring that implementing such an attack would be impractical for an attacker. The next application of PRNGs is in the casino industry, in which low-power and cost-effective automatic card shufflers for games like poker are becoming popular. This thesis explores a solution for optimal shuffling of a deck of cards.

The availability of several methods to unambiguously mark individual cells has strongly fostered the understanding of clonal developments in hematopoiesis and other stem cell driven regenerative tissues. While cellular barcoding is the method of choice for experimental studies, patients that underwent gene therapy carry a unique insertional mark within the transplanted cells originating from the integration of the retroviral vector. Close monitoring of such patients allows accessing their clonal dynamics, however, the early detection of events that predict monoclonal conversion and potentially the onset of leukemia are beneficial for treatment. We developed a simple mathematical model of a self-stabilizing hematopoietic stem cell population to generate a wide range of possible clonal developments, reproducing typical, experimentally and clinically observed scenarios. We use the resulting model scenarios to suggest and test a set of statistical measures that should allow for an interpretation and classification of relevant clonal dynamics. Apart from the assessment of several established diversity indices we suggest a measure that quantifies the extension to which the increase in the size of one clone is attributed to the total loss in the size of all other clones. By evaluating the change in relative clone sizes between consecutive measurements, the suggested measure, referred to as maximum relative clonal expansion (mRCE), proves to be highly sensitive in the detection of rapidly expanding cell clones prior to their dominant manifestation. This predictive potential places the mRCE as a suitable means for the early recognition of leukemogenesis especially in gene therapy patients that are closely monitored. Our model based approach illustrates how simulation studies can actively support the design and evaluation of preclinical strategies for the analysis and risk evaluation of clonal developments.

Die vorliegende Dissertation analysiert Textgeneratoren aus der Frühzeit der Computergeschichte, seit den 1970er Jahren, ausgehend von ihrem Quelltext. Variablenskripte, Joseph Weizenbaums "Eliza", Kenneth Colbys "Parry", frühe Adventurespiele und Terry Winograds "SHRDLU" werden auf die ihnen zugrundelegienden metaphorischen und algorithmischen Strukturen untersucht. Alle diese Programme lassen sich auf den Glauben der formallogischen Tradition zurückführen, Sprache und das in ihr repräsentierte Wissen von Welt stellten vollständig explizierbare und sogar formalisierbare Sachverhalte dar, wie er in Ludwig Wittgensteins "Tractatus" kulminiert. Technisch werden hier optionale Elemente in Baumstrukturen angeordnet und erzeugen scheinbar unerschöpfliche Varianz. Dem wird eine zweite Traditionslinie gegenübergestellt, die statt an Optionen an Operationen arbeitet und mit dem Dadaisten Tristan Tzara, der Wiederentdeckung des russischen Mathematikers Andrei Markov durch Claude Shannon und den Cutup-Experimenten von William S. Burroughs verbunden ist. Als deren Weiterführung beschreibt die Arbeit das im Rahmen dieser Promotion entwickelte Computerprogramm "Poetry Machine", einen auf semantischen Netzwerken basierenden, interaktiven Textgenerator, der sich selbständig mit Informationen aus dem Internet versorgt. Im Anhang findet sich die Übersetzung des grundlegenden Textes "Ein Beispiel statistischer Forschung am Text ''Eugen Onegin'' zur Verbindung von Proben in Ketten" von A. Markov ins Deutsche. / The present dissertation analyses text generators from the early times of computer history, since the 1970ies, starting from their source code. Variable scripts, Joseph Weizenbaum''s "Eliza", Kenneth Colby''s "Parry", early adventure games and Terry Winograd''s "SHRDLU" are investigated regarding their metaphorical and arithmetical structure. These programs can be traced back to the belief of the formal-logic tradition that language and the knowledge about the world represented by it can be fully explained and even be formalised, like it culminates in Ludwig Wittgenstein''s "Tractatus". Technically, optional elements are arranged in tree-like structures and generate seemingly endless variance. A second line of tradition is opposed to this, that works on operations rather than on options. It is linked to the dadaist Tristan Tzara, the re-discovery of the Russian mathematician Andrei Markov by Claude Shannon and the cutup-experiments of William S. Burroughs. As a continuation, the computer program "Poetry Machine" is described in detail, which was developed within the framework of the present dissertation. This interactive text generator is based on semantic networks and acquires its information autonomously from the internet. The translation of the fundamental text "An Example of Statistical Investigation of the Text ''Eugene Onegin'' Concerning the Connection of Samples in Chains" by A. Markov into German is given in the appendix.

On étudie le problème de la transmission de l'information à travers le canal AWGN en utilisant des réseaux. On commence par considérer des constellations infinies. Une nouvelle famille de réseaux obtenus par Construction A à partir de codes linéaires non binaires est proposée. Ces réseaux sont appelés LDA ("Low-Density Construction A") et sont caractérisés par des matrices de parité p-aires creuses, qui les mettent en relation directe avec les codes LPDC. Deux résultats sur leur possibilité d'atteindre la capacité de Poltyrev sont provés ; cela est d'abord démontré pour des poids des lignes logarithmiques des matrices de parité associées, puis pour des poids constants. Le deuxième résultat est basé sur certaines propriétés d'expansion des graphes de Tanner correspondants à ces matrices. Un autre sujet de ce travail concerne les constellations finies de réseaux. une nouvelle preuve est donnée du fait que des réseaux aléatoires obtenus par Construction A generale atteignent la capacité avec décodage de type "lattice decoding". Cela prolonge et améliore le travail de Erez et Zamir (2004), Ordentlich et Edrez (2012) Ling et Belfiore (2013). Cette preuve est basée sur les constellations de Coronoï et la multiplication par le coefficient de Wiener ("MMSE scaling") du siganl en sortie du canal. Finalement, ce résultat est adapté au cas des réseaux LDA, qui eux aussi atteignent la capacité avec le même procédé de transmission. Encore une fois, il est nécessaire d'exploiter les propriétés d'expansion des graphes de Tanner. A la fin de la dissertation, on présente un algorithme de décodage itératif et de type "message-passing" approprié au décodage des LDA en grandes dimensions. / The probleme of transmission of information over the AWGN channel using lattices is addressed. Firstly, infinite constellations are considered. A nex family of integer lattices built by means of construction A with non-binary linear condes is introduced. These lattices are called LPA (Low-Density Construction A) and are characterised by sparse p-ary parity-chedk matrices, that put them in direct relation with LPDC codes. Two results about the Poltyrev-capacity-archieving qualities of this family are proved, respectively for logarithmic row degree and constant row degree of the associated parity-check matrices. The second result is based on some expansion poperties of the Tanner graphs related to these matrices. Another topic of this work concerns finite lattice constellations. A new proff that heneral random Construction A lattices achieve capacity under lattice deconding is provided, continuing and pimproving the work of Erez and Zamir (2004), Ordentlich an Erez (2012), and Ling and Belfiore (2013). This proof is based on Voronoi lattice constellations and MMSE scaling of the channel output. Finally, this approach is adapted to the LDA case abd ut us scgiwn tgat LDA lattices achive capacity with the ame transmission scheme, too. Once again, it is necessary to exploit the expansion properties of the Tanner graphs. At he end of the dissertation, an iterative message-passing algorithm suitable for decoding LDA lattices in high dimensions is presented.

The aim of this study was to investigate how selected municipalities’ use social media, with a focus on how they are working to increase the dialogue between municipalities’ and residents. To answer the purpose of the study three questions has been formulated: how do the communicators use social media in their daily work? What opportunities and challenges are the municipalities’ experiencing with Facebook? How do they work with Facebook to increase dialogue with citizens? The theories that has been used in this study is Cutlip’s and Grunig’s public relations theories, Shannon and weavers communication model, Cutlip’s and Heath’s theory of issue management and Jenkins theory of convergence culture. The method that has been used in this study is qualitative semi-structured interviews and the analysis is done with a thematic text analysis. The material of this study contained interviews of four communicator officers that are responsible for social media in the municipalities’.    The results of the semi-structured interviews showed that the communicator officers used social media to quickly, easily and cheaply connect many citizens in comparison with the traditional media. The biggest opportunity with Facebook for municipalities’ was to improve issue management by spreading the information faster and have an improved dialog with the citizens. The biggest challenge was to think more strategically how to enhance the use of Facebook. The communicator officers try to invite citizens to dialogue by presenting information that citizens want comment and debate about. Municipalities’ also will have meetings with PR agencies to improve the dialog with the citizens in Facebook.

Multiple Sequenzalignments (MSAs) von homologen Proteinen sind nützliche Werkzeuge, um kompensatorische Mutationen zwischen nicht-konservierten Residuen zu charakterisieren. Die Identifizierung dieser Residuen in MSAs ist eine wichtige Aufgabe um die strukturellen Grundlagen und molekularen Mechanismen von Proteinfunktionen besser zu verstehen. Trotz der vielen Anzahl an Literatur über kompensatorische Mutationen sowie über die Sequenzkonservierungsanalyse für die Erkennung von wichtigen Residuen, haben vorherige Methoden meistens die biochemischen Eigenschaften von Aminosäuren nicht mit in Betracht gezogen, welche allerdings entscheidend für die Erkennung von kompensatorischen Mutationssignalen sein können. Jedoch werden kompensatorische Mutationssignale in MSAs oft durch das Rauschen verfälscht. Aus diesem Grund besteht ein weiteres Problem der Bioinformatik in der Trennung signifikanter Signale vom phylogenetischen Rauschen und beziehungslosen Paarsignalen. Das Ziel dieser Arbeit besteht darin Methoden zu entwickeln, welche biochemische Eigenschaften wie Ähnlichkeiten und Unähnlichkeiten von Aminosäuren in der Identifizierung von kompensatorischen Mutationen integriert und sich mit dem Rauschen auseinandersetzt. Deshalb entwickeln wir unterschiedliche Methoden basierend auf klassischer- und quantum Informationstheorie sowie multiple Testverfahren. Unsere erste Methode basiert auf der klassischen Informationstheorie. Diese Methode betrachtet hauptsächlich BLOSUM62-unähnliche Paare von Aminosäuren als ein Modell von kompensatorischen Mutationen und integriert sie in die Identifizierung von wichtigen Residuen. Um diese Methode zu ergänzen, entwickeln wir unsere zweite Methode unter Verwendung der Grundlagen von quantum Informationstheorie. Diese neue Methode unterscheidet sich von der ersten Methode durch gleichzeitige Modellierung ähnlicher und unähnlicher Signale in der kompensatorischen Mutationsanalyse. Des Weiteren, um signifikante Signale vom Rauschen zu trennen, entwickeln wir ein MSA-spezifisch statistisches Modell in Bezug auf multiple Testverfahren. Wir wenden unsere Methode für zwei menschliche Proteine an, nämlich epidermal growth factor receptor (EGFR) und glucokinase (GCK). Die Ergebnisse zeigen, dass das MSA-spezifisch statistische Modell die signifikanten Signale vom phylogenetischen Rauschen und von beziehungslosen Paarsignalen trennen kann. Nur unter Berücksichtigung BLOSUM62-unähnlicher Paare von Aminosäuren identifiziert die erste Methode erfolgreich die krankheits-assoziierten wichtigen Residuen der beiden Proteine. Im Gegensatz dazu, durch die gleichzeitige Modellierung ähnlicher und unähnlicher Signale von Aminosäurepaare ist die zweite Methode sensibler für die Identifizierung von katalytischen und allosterischen Residuen.

Le point de départ de ce travail est la thèse réalisée par Pascal Vrignat sur la modélisation de niveaux de dégradation d’un système dynamique à l’aide de Modèles de Markov Cachés (MMC), pour une application en maintenance industrielle. Quatre niveaux ont été définis : S1 pour un arrêt de production et S2 à S4 pour des dégradations graduelles. Recueillant un certain nombre d’observations sur le terrain dans divers entreprises de la région, nous avons réalisé un modèle de synthèse à base de MMC afin de simuler les différents niveaux de dégradation d’un système réel. Dans un premier temps, nous identifions la pertinence des différentes observations ou symboles utilisés dans la modélisation d’un processus industriel. Nous introduisons ainsi le filtre entropique. Ensuite, dans un but d’amélioration du modèle, nous essayons de répondre aux questions : Quel est l’échantillonnage le plus pertinent et combien de symboles sont ils nécessaires pour évaluer au mieux le modèle ? Nous étudions ensuite les caractéristiques de plusieurs modélisations possibles d’un processus industriel afin d’en déduire la meilleure architecture. Nous utilisons des critères de test comme les critères de l’entropie de Shannon, d’Akaike ainsi que des tests statistiques. Enfin, nous confrontons les résultats issus du modèle de synthèse avec ceux issus d’applications industrielles. Nous proposons un réajustement du modèle pour être plus proche de la réalité de terrain. / As part of preventive maintenance, many companies are trying to improve the decision support of their experts. This thesis aims to assist our industrial partners in improving their maintenance operations (production of pastries, aluminum smelter and glass manufacturing plant). To model industrial processes, different topologies of Hidden Markov Models have been used, with a view to finding the best topology by studying the relevance of the model outputs (also called signatures). This thesis should make it possible to select a model framework (a framework includes : a topology, a learning & decoding algorithm and a distribution) by assessing the signature given by different synthetic models. To evaluate this « signature », the following widely-used criteria have been applied : Shannon Entropy, Maximum likelihood, Akaike Information Criterion, Bayesian Information Criterion and Statistical tests.

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-05-16T23:56:29Z No. of bitstreams: 1 EDMAR JOSÉ DO NASCIMENTO – TESE (PPGEE) 2017.pdf: 1146136 bytes, checksum: 66fa0c285fd895d4aa000dd5ad1d1eef (MD5) / Made available in DSpace on 2018-05-16T23:56:29Z (GMT). No. of bitstreams: 1 EDMAR JOSÉ DO NASCIMENTO – TESE (PPGEE) 2017.pdf: 1146136 bytes, checksum: 66fa0c285fd895d4aa000dd5ad1d1eef (MD5) Previous issue date: 2018-04-18 / Protocolos para a distribuição quântica de chaves (DQC) permitem que duas partes (Alice e Bob) compartilhem uma chave secreta que pode ser usada para fins criptográficos. A segurança do protocolo é baseada em propriedades da mecânica quântica, ao invés de hipóteses computacionais. Na distribuição quântica de chaves com variáveis contínuas (DQCVC), a informação é codificada nas amplitudes de quadratura do campo eletromagnético quantizado. Quando implementado com variáveis contínuas, o aparato usado na DQC é consideravelmente mais simples que nas implementações convencionais com variáveis discretas, já que se pode utilizar a medição do tipo homódina, ao invés da detecção de fótons. Uma vez realizada a medida, ainda se faz necessária uma etapa de processamento clássico, denominada de reconciliação da informação, a fim de que Alice e Bob possam compartilhar uma cadeia comum de bits. Para que a DQCVC possa ser realizada em distâncias razoáveis (superiores a 30 km), o processo de reconciliação precisa ser feito com eficiências elevadas (superiores a 90%). Entretanto, eficiências dessa ordem para baixas SNRs (signal-to-noise ratio - razão sinal ruído) requerem o uso de códigos clássicos de comprimento bastante elevado e, assim, são difíceis de serem alcançadas. Nesta tese, se propõe o uso dos mapas de Shannon-Kotel’nikov na preparação dos estados quânticos que são usados na DQCVC. Com a utilização desses mapas, é possível aumentar a SNR entre Alice e Bob sem aumentar a variância da modulação de Alice. Dessa forma, o processo de reconciliação se torna mais simples, pois eficiências de reconciliação mais altas são mais facilmente alcançadas em SNRs maiores. Como contribuições desta tese têm-se: a proposição de um protocolo; a definição de um cenário de simulação e a análise do protocolo para dois tipos de mapas (a espiral uniforme de Arquimedes e as curvas geodésicas em um toro planar). / Quantum key distribution (QKD) protocols allow two parties, Alice and Bob, to share a secret key that may be used for cryptographic purposes. The security of QKD is based on quantum mechanics properties instead of computational assumptions. In continuous-variable quantum key distribution (CVQKD), the information is encoded in the quadrature amplitudes of the quantized electromagnetic field. When QKD is implemented with continuous variables, hardware components are much simpler than their discrete variables equivalents. This is mainly due to homodyne detection instead of photon detection. After measuring the transmitted states, it is still necessary to carry out a classical processing stage known as information reconciliation. This stage allows Alice and Bob to share a common sequence of bits. In order to deploy CVQKD over reasonable distances (over 30 km), reconciliation must be done at high efficiencies (over 90%). However, such high efficiencies for low SNRs (signal-to-noise ratio) require long length classical codes and are difficult to be reached. In this thesis, we propose to use Shannon-Kotel’nikov maps for preparing quantum states in CVQKD. By using these maps, it is possible to increase the SNR between Alice and Bob, without increasing Alice’s variance. Thus, reconciliation becomes easier because higher reconciliation efficiencies are more easily reached for higher SNRs. The contributions of this theses are: the proposal of a CVQKD protocol; the statement of a simulation scenario; the analysis of the proposed protocol for two kinds of maps (uniform Archimedes’ spiral and geodesic curves on a flat torus).

Made available in DSpace on 2016-08-17T14:53:17Z (GMT). No. of bitstreams: 1 Ulysses Santos Sousa.pdf: 1410915 bytes, checksum: 88235f7f4a3bc07a4da1b27c23dc71ca (MD5) Previous issue date: 2011-05-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Cancer is one of the biggest health problems worldwide, and the breast cancer is the one that causes more deaths among women. Also it is the second most frequent type in the world. The chances of survival for a patient with breast cancer increases the sooner this disease is discovered. Several Computer Aided Detection/Diagnosis Systems has been used to assist health professionals. This work presents a methodology to discriminate and classify mammographic tissues regions in mass and non-mass. For this purpose the Shannon-Wiener‟s Diversity Index, which is applied to measure the biodiversity in ecosystem, is used to describe pattern of breast image region with four approaches: global, in circles, in rings and directional. After, a Support Vector Machine is used to classify the regions in mass and non-mass. The methodology presents promising results for classification of mammographic tissues regions in mass and non-mass, achieving 99.85% maximum accuracy. / O câncer é um dos maiores problemas de saúde mundial, sendo o câncer de mama o que mais causa óbito entre as mulheres e o segundo tipo mais freqüente no mundo. As chances de uma paciente sobreviver ao câncer de mama aumentam à medida que a doença é descoberta mais cedo. Diversos Sistemas de Detecção e Diagnóstico auxiliados por computador (Computer Aided Detection/Diagnosis) têm sido utilizados para auxiliar profissionais de saúde. Este trabalho apresenta uma metodologia de discriminação e classificação de regiões de tecidos de mamografias em massa e não massa. Para este propósito utiliza-se o Índice de Diversidade de Shannon-Wiener, comumente aplicado para medir a biodiversidade em um ecossistema, para descrever padrões de regiões de imagens de mama com quatro abordagens: global, em círculos, em anéis e direcional. Em seguida, utiliza-se o classificador Support Vector Machine para classificar estas regiões em massa e não massa. A metodologia apresenta resultados promissores para a classificação de regiões de tecidos de mamografia em massa e não massa, obtendo uma acurácia máxima de 99,85%.