Trusted platform modules (TPMs) are hardware modules that are bound to a computer's motherboard, that are being included in many desktops and laptops. Augmenting computers with these hardware modules adds powerful functionality in distributed settings, allowing us to reason about the security of these systems in new ways. In this dissertation, I study the functionality of TPMs from a theoretical as well as an experimental perspective. On the theoretical front, I leverage various features of TPMs to construct applications like random oracles that are impossible to implement in a standard model of computation. Apart from random oracles, I construct a new cryptographic primitive which is basically a non-interactive form of the standard cryptographic primitive of oblivious transfer. I apply this new primitive to secure mobile agent computations, where interaction between various entities is typically required to ensure security. I prove these constructions are secure using standard cryptographic techniques and assumptions. To test the practicability of these constructions and their applications, I performed an experimental study, both on an actual TPM and a software TPM simulator which has been enhanced to make it reflect timings from a real TPM. This allowed me to benchmark the performance of the applications and test the feasibility of the proposed extensions to standard TPMs. My tests also show that these constructions are practical.

Smart contracts are digital agreements stored and executed on a blockchain. With smart contracts, multiple parties can enter into an agreement whose correct execution is guaranteed by the underlying blockchain. However, there is no inherent way for smart contracts to access data APIs external to the blockchain they reside on, which is needed in order to expand their usefulness. This thesis investigates two approaches of feeding data to a smart contract on the Ethereum blockchain, with regard to the performance metrics gas cost, block delay, and network latency. The investigation is set in the context of train travel where the time of arrival of a train at its destination is retrieved to the smart contract. Receiving and aggregating submissions from varying numbers of passengers is compared to retrieving this data from the dedicated open API provided by Trafikverket using the Chainlink framework. Through experiments, involving issuing transactions and monitoring them, it was found that in the case of passenger submissions with aggregation the gas costs had a linear relationship to the amount of passengers submitting data. Compared to lower amounts, the block delay for passenger submissions started seeing an increase at 100 to 300 submissions whereas it was more or less constant for aggregations. Furthermore, there was no noticeable trend for increase in network delay with increase of submissions. Conclusively, with regard to all performance metrics, it was found that in all cases involving more than five passengers it was cheaper to use Chainlink to fetch data from Trafikverket.

Texte remanié de: Thèse de doctorat--Épigraphie grecque--Paris, EPHE, 2000.

Ce mémoire vise à appliquer l’étude des oracles en Grèce au cas longtemps malmené de l’oracle du rempart de bois. Alors que les historiens modernes deviennent de plus en plus critiques face à la littérature oraculaire grâce aux découvertes de l’épigraphie, cet oracle semble résister à cette nouvelle vague : tout et son contraire ont été allégué afin de le préserver de l’étiquette de post eventum. À la lumière du cadre historique dans lequel Hérodote a conçu ses Histoires, nous serons en mesure de décortiquer les éléments constitutifs de cet oracle qui prédit l’issue de la Seconde Guerre médique et selon lequel les Athéniens trouvèrent leur salut derrière le désormais célèbre « rempart de bois ». Nous nous attarderons finalement au dit « Décret de Thémistocle », trouvé à Trézène et commandant l’évacuation d’Athènes. Au terme de ce mémoire, l’épisode du rempart de bois apparaîtra définitivement comme post eventum. / The aim of this thesis is to apply the study of oracles in Greece to the long mistreated case of the oracle of the Wooden Wall. While modern historians are becoming increasingly critical of oracular literature since the discoveries of epigraphy, this oracle appears to resist this new wave: anything and everything were alleged to preserve it from the label of post eventum. The components of this oracle, which predicts the outcome of the second Persian War, and according to which the Athenians would find their salvation behind the now famous Wooden Wall, will be dissected in light of the historical context surrounding Herodotus’ work. The “Decree of Themistocles” found in Troezen, which ordered the evacuation of Athens, will also be addressed. In the conclusion of this thesis, the episode of the wooden wall will be seen to be definitely post eventum.

Ce mémoire vise à appliquer l’étude des oracles en Grèce au cas longtemps malmené de l’oracle du rempart de bois. Alors que les historiens modernes deviennent de plus en plus critiques face à la littérature oraculaire grâce aux découvertes de l’épigraphie, cet oracle semble résister à cette nouvelle vague : tout et son contraire ont été allégué afin de le préserver de l’étiquette de post eventum. À la lumière du cadre historique dans lequel Hérodote a conçu ses Histoires, nous serons en mesure de décortiquer les éléments constitutifs de cet oracle qui prédit l’issue de la Seconde Guerre médique et selon lequel les Athéniens trouvèrent leur salut derrière le désormais célèbre « rempart de bois ». Nous nous attarderons finalement au dit « Décret de Thémistocle », trouvé à Trézène et commandant l’évacuation d’Athènes. Au terme de ce mémoire, l’épisode du rempart de bois apparaîtra définitivement comme post eventum. / The aim of this thesis is to apply the study of oracles in Greece to the long mistreated case of the oracle of the Wooden Wall. While modern historians are becoming increasingly critical of oracular literature since the discoveries of epigraphy, this oracle appears to resist this new wave: anything and everything were alleged to preserve it from the label of post eventum. The components of this oracle, which predicts the outcome of the second Persian War, and according to which the Athenians would find their salvation behind the now famous Wooden Wall, will be dissected in light of the historical context surrounding Herodotus’ work. The “Decree of Themistocles” found in Troezen, which ordered the evacuation of Athens, will also be addressed. In the conclusion of this thesis, the episode of the wooden wall will be seen to be definitely post eventum.

Cette thèse a pour but de dresser un panorama complet des croyances de Xénophon en la divination. À l’aide d’une analyse rigoureuse de la totalité des œuvres de cet auteur antique pendant longtemps déprécié, il ressort que le problème de la consultation des dieux, loin d’être abordé de manière anecdotique et spontanée à la façon d’un legs de la tradition que la pensée critique n’a pas touchée, est au contraire un élément essentiel de la formation d’une réflexion profonde sur la piété et plus généralement les rapports qu’entretiennent les hommes avec les dieux. D’autre part, en raison du zèle de Xénophon à avoir rapporté des récits ou des réflexions à propos de la divination, cette analyse offre l’occasion de mieux comprendre les subtilités de cette pratique rituelle logée au cœur de la religion grecque et qui ne saurait être réduite à une forme de superstition. / This thesis aims to provide a complete overview of the beliefs of Xenophon about divination. Using a rigorous analysis of all the works of this ancient author who has long been depreciated, it seems clear that the problem of the consultation of the gods, far from being addressed incidentally and spontaneously like a traditional legacy that critical thinking has not reached, is on the contrary an essential element in the formation of a deep thinking on piety, and more generally of the relationships between men and gods. On the other hand, due to Xenophon’s zeal to have reported stories or thoughts about divination, this analysis provides an opportunity to a better understanding of the intricacies of this ritual lying at the core of Greek religion and that can not be reduced to a form of superstition.

This thesis makes fundamental computational and statistical advances in testing and estimation, making critical progress in theory and application of classical statistical methods like classification, regression and hypothesis testing, and understanding the relationships between them. Our work connects multiple fields in often counter-intuitive and surprising ways, leading to new theory, new algorithms, and new insights, and ultimately to a cross-fertilization of varied fields like optimization, statistics and machine learning. The first of three thrusts has to do with active learning, a form of sequential learning from feedback-driven queries that often has a provable statistical advantage over passive learning. We unify concepts from two seemingly different areas—active learning and stochastic firstorder optimization. We use this unified view to develop new lower bounds for stochastic optimization using tools from active learning and new algorithms for active learning using ideas from optimization. We also study the effect of feature noise, or errors-in-variables, on the ability to actively learn. The second thrust deals with the development and analysis of new convex optimization algorithms for classification and regression problems. We provide geometrical and convex analytical insights into the role of the margin in margin-based classification, and develop new greedy primal-dual algorithms for non-linear classification. We also develop a unified proof for convergence rates of randomized algorithms for the ordinary least squares and ridge regression problems in a variety of settings, with the purpose of investigating which algorithm should be utilized in different settings. Lastly, we develop fast state-of-the-art numerically stable algorithms for an important univariate regression problem called trend filtering with a wide variety of practical extensions. The last thrust involves a series of practical and theoretical advances in nonparametric hypothesis testing. We show that a smoothedWasserstein distance allows us to connect many vast families of univariate and multivariate two sample tests. We clearly demonstrate the decreasing power of the families of kernel-based and distance-based two-sample tests and independence tests with increasing dimensionality, challenging existing folklore that they work well in high dimensions. Surprisingly, we show that these tests are automatically adaptive to simple alternatives and achieve the same power as other direct tests for detecting mean differences. We discover a computation-statistics tradeoff, where computationally more expensive two-sample tests have a provable statistical advantage over cheaper tests. We also demonstrate the practical advantage of using Stein shrinkage for kernel independence testing at small sample sizes. Lastly, we develop a novel algorithmic scheme for performing sequential multivariate nonparametric hypothesis testing using the martingale law of the iterated logarithm to near-optimally control both type-1 and type-2 errors. One perspective connecting everything in this thesis involves the closely related and fundamental problems of linear regression and classification. Every contribution in this thesis, from active learning to optimization algorithms, to the role of the margin, to nonparametric testing fits in this picture. An underlying theme that repeats itself in this thesis, is the computational and/or statistical advantages of sequential schemes with feedback. This arises in our work through comparing active with passive learning, through iterative algorithms for solving linear systems instead of direct matrix inversions, and through comparing the power of sequential and batch hypothesis tests.

No desenvolvimento de software, a qualidade do produto está diretamente relacionada à qualidade do processo de desenvolvimento. Diante disso, atividades de Verificação, Validação & Teste (VV&T) realizadas por meio de métodos, técnicas e ferramentas são de extrema necessidade para o aumento da produtividade, qualidade e diminuição de custos no desenvolvimento de software. Do mesmo modo, técnicas e critérios contribuem para a produtividade das atividades de teste. Um ponto crucial para o teste de software é sua automatização, tornando as atividades mais confiáveis e diminuindo significativamente os custos de desenvolvimento. Na automatização dos testes, os oráculos são essenciais, representando um mecanismo (programa, processo ou dados) que indica se a saída obtida para um caso de teste está correta. Este trabalho de mestrado utiliza a ideia de mutação para criar implementações alternativas de oráculos de teste e, assim, avaliar a sua qualidade. O teste de mutação se refere à criação de versões do sistema em desenvolvimento com pequenas alterações sintáticas de código. A mutação possui alta eficácia na detecção de defeitos e é bastante flexível na sua aplicação, podendo ser utilizada em diversos tipos de artefatos. Adicionalmente, este trabalho propõe operadores de mutação específicos para oráculos, implementa uma ferramenta de apoio à utilização desses operadores para oráculos e também descreve um estudo empírico dos operadores, destacando benefícios e desafios associados ao seu uso. / In software development, product quality is directly related to the quality of the development process. Therefore, activities of Verification, Validation & Testing (VV&T) performed by methods, techniques and tools are urgently required to increase productivity, quality and cost reduction in software development. Similarly, testing technique and criteria contribute to the productivity of test activities. A crucial point for the software testing automation is making the most reliable activities and significantly reducing development costs. Regarding software testing automation, test oracles are essential, representing an mechanism (program, process or data) to indicate whether the actual output for a given test case is correct. This masters thesis aims to explore concepts of mutation testing to create alternative implementations of the oracle procedure and thus assess their quality. Mutation testing refers to the creation of system development versions with minor syntactic code changes. It has high efficiency on defects detecting and it is very flexible in its application and it is being used in various types of artifacts. This work also proposes specific mutation operators for oracles, implements an useful support tool for using these oracle mutation operators and conducts an empirical study of operators, highlighting benefits and challenges associated with their use.

O propósito desta dissertação é apresentar algumas idéias sobre o emprego das palavras relacionadas à visão no texto do Livro I das Histórias de Heródoto. O principal destaque é dado à relação entre ver e saber e as investigações de Heródoto. O segundo propósito, decorrente do primeiro, é verificar a importância dos oráculos no Livro I e buscar a relação (se existe) entre oráculos, sonhos, visões e a busca do conhecimento. / The purpose of this dissertation is to show some ideas about the use of words related to sight in the text of HerodotusHistories, Book I . The main focus is given to the existing relationship between seeing and knowing and Herodotus researches. The second purpose, built from the first one, is to evaluate the importance of oracles described in Book I and to seek the relationship of (if it exists) oracles, dreams, visions and the search for knowledge.

Software testing is one of the most important Software Engineering processes, being the primary activity to check the conformance between the software requirements and its actual behavior. The automation of software testing activities is essential to certify productivity and effectiveness in such activities. Test automation leads testing activities to be conducted under systematic and accurate criteria, raising the chance of testers to reveal faults or inconsistencies. Test oracles are elementary members in software testing automation, being the mechanism responsible for indicating the correctness of software outputs. In testing environments, test oracles can be effectively implemented based on several sources of information about the Software Under Testing (SUT): software specifications, assertions, formal methods (Finite State Machines (FSM), formal specifications, etc, machine-learning methods, and metamorphic relations. Regardless of the implementation strategy, test oracles are vulnerable to false positive/negative verdicts, configuring what the literature describes as the oracle problem. Therefore, test oracles are a non-trivial and challenging object of studies of the software engineering research area. SUTs outputs in unusual formats make it harder the oracle problem. Audio, images, three-dimensional objects, virtual reality environments, complex statistical compositions, etc, are examples of non-trivial output formats. In the software testing context, SUTs with unusual outputs can be called complex-output systems. In this doctorate dissertation, we propose and evaluate a novel test oracle approach for complex-output systems called feature-based test oracles. The purpose of feature-based test oracles is the appropriation of a processing image technique called Content-Based Image Retrieval (CBIR) to collect information from features extracted from the SUTs outputs to compose test oracles. Given a query image, CBIR combines feature extraction and similarity functions to alleviate the problem of searching for digital images in large databases. In previous research, we have integrated CBIR concepts in a testing framework to support the automation of testing activities in processing image systems and systems with Graphical User Interfaces (GUI). In this doctorate dissertation, we extended that framework and its concepts to general complex-output systems, addressing the feature-based test oracle approach. We use Text-To-Speech (TTS) systems to validate empirically our test oracle technique. Through the results of five empirical analyses, three of them conducted in line with problems of a real-world industry TTS system, show the proposed technique is a valuable instrument to automate testing activities and alleviate practitioners efforts on testing complex output systems. We conclude the proposed test oracles are effective because they systematically evaluate the SUTs sensorial output rather than produce verdicts based on subjective specifications. As future work, we plan to conduct investigations towards the reduction of false positives/negatives and the association of the test oracles with machine learning techniques and metamorphic relations. / Teste de Software é um dos processos mais importantes da Engenharia de Software, sendo a principal atividade para averiguar a conformidade de requisitos de software e suas saídas. A automatização das atividades de teste é essencial para conferir produtividade e efetividade em tais atividades. A automatização faz com que atividades de teste sejam conduzidas sob critérios sistemáticos e precisos, aumentando a chance dos testadores de revelarem falhas ou inconcistências. Oráculos de teste são membros elementares na automatização do teste de software, sendo o mecanismo responsável por indicar a corretude das saídas do softwre. Em ambientes de teste, oráculos de teste podem ser efetivamente implementados com base em diversos fontes de informação sobre o sistema em teste: especificações de software, assertivas, métodos formais (máquinas de estados finitas, especificações formais, etc), métodos de aprendizagem de máquina e relações metamórficas. Independente da estratégia de implementação, oráculos de teste são vulneráveis a veridictos de falsos positivos/negativos, configurando o que é apresentado na literatura como O problema do Oráculo. Então, na área de engenharia de software, oráculos de teste são objetos de estudo não-triviais e desafiadores. O problema de oráculo é potencializado quando as saídas do sistema em teste são dadas em formatos não triviais como, por exemplo, audio, imagens, objetos tridimensionais, ambientes de realidade virtual, composições estatísticas complexas, etc. No contexto do teste de software, sistemas com saídas não triviais podem ser chamados de sistemas com saídas complexas. Esta tese de doutorado propões e avalia uma nova estratégia de oráculo de teste para sistemas com saídas complexas. O propósito de tal estratégia é a apropriação da técnica de processamento de imagem conhecida como CBIR (Recuperação de Imagem Basead em Conteúdo CBIR) para coletar informações de características extratídas do sistema em teste, compondo oráculos de teste. A partir de uma imagem de busca, o CBIR combina extração de características e funções de similaridade para aliviar problemas de busca em grandes based de imagens digitais. Em pesquisas anteriores, conceitos de CBIR foram integrados em um arcabouço de teste para apoiar a automatização de atividades de teste em systemas de processamento de imagens e sistemas com interfaces gráficas. Esta tese de doutorado estende o arcabouço e seus conceitos para sistemas com saídas complexas em geral. Sistemas Texto-Fala (TTS) foram utlizados para validações empíricas. Os resultados de seis análises empíricas, duas delas condizidas em consonância com problemas de um TTS industrial, revelam que a técnica proposta é um valioso instrumento para automatizar atividaes de teste e aliviar esforços de profissionais da indústria ao teste sistemas com saídas complexas. Conclui-se que a efetividade dos oráculos de teste propostos são devido às sistemáticas análises do conteúdo das saídas dos sistemas em teste, em vez da análises de especificações subjetivas. Os trabalhos futuros vislumbrados devem ser conduzidos no intuito de reduzir número de falsos positivos/negativos e a associação dos oráculos de teste com técnicas de aprendizado de máquina e relações metamórficas.