This thesis aims to address several issues emerging in the new digital world. Using Trusted Computing as the paradigmatic example of regulation though code that tries to address the cyber security problem that occurs, where the freedom of the user to reconfigure her machine is restricted in exchange for greater, yet not perfect, security. Trusted Computing is a technology that while it aims to protect the user, and the integrity of her machine and her privacy against third party users, it discloses more of her information to trusted third parties, exposing her to security risks in case of compromising occurring to that third party. It also intends to create a decentralized, bottom up solution to security where security follows along the arcs of an emergent “network of trust”, and if that was viable, to achieve a form of code based regulation. Through the analysis attempted in this thesis, we laid the groundwork for a refined assessment, considering the problems that Trusted Computing Initiative (TCI) faces and that are based in the intentional, systematic but sometimes misunderstood and miscommunicated difference (which as we reveal results directly in certain design choices for TC) between the conception of trust in informatics (“techno-trust”) and the common sociological concept of it. To reap the benefits of TCI and create the dynamic “network of trust”, we need the sociological concept of trust sharing the fundamental characteristics of transitivity and holism which are absent from techno-trust. This gives rise to our next visited problems which are: if TC shifts the power from the customer to the TC provider, who takes on roles previously reserved for the nation state, then how in a democratic state can users trust those that make the rules? The answer lies partly in constitutional and human rights law and we drill into those functions of TC that makes the TCI provider comparable to state-like and ask what minimal legal guarantees need to be in place to accept, trustingly, this shift of power. Secondly, traditional liberal contract law reduces complex social relations to binary exchange relations, which are not transitive and disrupt rather than create networks. Contract law, as we argue, plays a central role for the way in which the TC provider interacts with his customers and this thesis contributes in speculating of a contract law that does not result in atomism, rather “brings in” potentially affected third parties and results in holistic networks. In the same vein, this thesis looks mainly at specific ways in which law can correct or redefine the implicit and democratically not validated shift of power from customer to TC providers while enhancing the social environment and its social trust within which TC must operate.

Many Latin American countries which underwent democratic regime transformations within the last thirst years have seemingly stalled. Unable to meet the demands of their citizens, which grow increasingly restless and confrontational, they have become subjected to a series of economic and political crises. Contemporary democratic theorists are at a loss to explain why this region has failed to deepen over time. The purpose of this paper is threefold: it questions the analytic utility of contemporary liberal and representative models, it argues for the inclusion of an alternative process-oriented model provided by Charles Tilly (2007), and tests this model through a partial application to Bolivia from 1993-2009 in hopes of elucidating a clearer state of democratization than contemporary models offer. The analysis portion focuses on the incorporation of networks of trust into public politics, and determines what effect(s) this had on Bolivian democracy during the time period under review. It is hypothesized that an increase in the integration of interpersonal trust networks with public politics will result in democratization, which is measured through changes in demand incorporation, protection, equality, and state-society accountability. A diachronic analytical narrative is constructed to identify the mechanisms and signs associated with the emergence and incorporation of trust networks into public politics and then evaluated in terms of state-society transformation. The findings suggest that new trust networks were created following the political restructuring done during the Sánchez de Lozada presidency, deepened over the next four presidencies, and integrated in their fullest capacity during the first part of Evo Morales's term. This process affected the contemporary representative and structural nature of the state itself, and shows positive changes in demand incorporation, protection, equality, and state-society accountability. Finally, it is concluded that when compared with popular measures of democracy, this model has more explanatory power, and Bolivia did democratize within the period of analysis.

Distributed systems like e-commerce and e-market places, peer-to-peer networks, social networks, and mobile ad hoc networks require cooperation among the participating entities to guarantee the formation and sustained existence of network services. The reliability of interactions among anonymous entities is a significant issue in such environments. The distributed entities establish connections to interact with others, which may include selfish and misbehaving entities and result in bad experiences. Therefore, trustworthiness evaluation using trust management techniques has become a significant issue in securing these environments to allow entities decide on the reliability and trustworthiness of other entities, besides it helps coping with defection problems and stimulating entities to cooperate. Recent models on evaluating trustworthiness in distributed systems have heavily focused on assessing trustworthiness of entities and isolate misbehaviours based on single trust metrics. Less effort has been put on the investigation of the subjective nature and differences in the way trustworthiness is perceived to produce a composite multidimensional trust metrics to overcome the limitation of considering single trust metric. In the light of this context, this thesis concerns the evaluation of entities’ trustworthiness by the design and investigation of trust metrics that are computed using multiple properties of trust and considering environment. Based on the concept of probabilistic theory of trust management technique, this thesis models trust systems and designs cooperation techniques to evaluate trustworthiness in mobile ad hoc networks (MANETs). A recommendation based trust model with multi-parameters filtering algorithm, and multidimensional metric based on social and QoS trust model are proposed to secure MANETs. Effectiveness of each of these models in evaluating trustworthiness and discovering misbehaving nodes prior to interactions, as well as their influence on the network performance has been investigated. The results of investigating both the trustworthiness evaluation and the network performance are promising.

Submitted by Nadir Basilio (nadirsb@uninove.br) on 2017-03-01T21:34:06Z No. of bitstreams: 1 Ronan Kayano Genoino.pdf: 2728242 bytes, checksum: de5f6fa2af63f54ea2a868aa133a9a36 (MD5) / Made available in DSpace on 2017-03-01T21:34:06Z (GMT). No. of bitstreams: 1 Ronan Kayano Genoino.pdf: 2728242 bytes, checksum: de5f6fa2af63f54ea2a868aa133a9a36 (MD5) Previous issue date: 2016-12-14 / This study aimed to verify which leads an actor to have greater centrality in the trust networks, that verifies the relationship between organizational commitment, technical ability, and time in the team (independent variables) with the centrality of the athletes in the trust networks of team sports (dependent variable). This research was based on the theory of social networks, one of the topics most discussed in the social sciences in the last decade, specifically the trust networks, a kind of informal network that is formed by interpersonal trust relationships between the members of an organization. The study was a qualitative research with an exploratory descriptive done with athletes of the Centro Olímpico de Treinamento e Pesquisa. Questionnaires were applied in 49 athletes from three different teams, to collect socio-metric data, to measure the trust network (used the UCINET software), organizational commitment, technical ability of players and time in the team. Moreover, semi-structured interviews were conducted among coaches of the three teams. The results indicated that the research question in this project was answered, since the field provided empirical evidence about a positive relationship between organizational commitment, time in the team, technical ability, and the centrality of athletes in trust networks. The main practical application is the parallel that can be done with the managerial field, in which more committed and qualified professionals, with more time in the organizations, can enjoy greater confidence within the corporate environment, resulting in better organizational performance. / O presente trabalho teve como objetivo verificar o que leva um ator a ter maior centralidade nas redes de confiança, verificando a relação entre o comprometimento organizacional, a qualidade técnica e o tempo na equipe (variáveis independentes) com a centralidade dos atletas nas redes de confiança de equipes esportivas (variável dependente). A pesquisa teve como base a teoria das redes sociais, mais especificamente as redes de confiança, um tipo de rede informal que é formada pelas relações de confiança interpessoal entre os membros de uma organização. O estudo foi uma pesquisa qualitativa com caráter exploratório-descritivo, feita com atletas do Centro Olímpico de Treinamento e Pesquisa. Questionários foram aplicados em 49 atletas de três equipes diferentes. Foram coletados dados sócio-métricos, para mensuração da rede de confiança (utilizou-se o software UCINET), comprometimento organizacional, qualidade técnica dos jogadores e tempo na equipe. Além disso, foram realizadas entrevistas semi-estruturadas com os treinadores das três equipes. Os resultados obtidos indicaram que a questão de pesquisa do presente estudo foi respondida, uma vez que o campo forneceu evidências empíricas da existência de uma relação positiva entre o comprometimento organizacional, tempo na equipe e qualidade técnica e a centralidade dos atletas nas redes de confiança. A principal contribuição para a prática é o paralelo que pode ser feito com o campo gerencial, em que profissionais mais comprometidos e qualificados e com mais tempo dentro das organizações podem gozar de maior confiança dentro do ambiente corporativo, resultando em um melhor desempenho organizacional.

Distributed systems like e-commerce and e-market places, peer-to-peer networks, social networks, and mobile ad hoc networks require cooperation among the participating entities to guarantee the formation and sustained existence of network services. The reliability of interactions among anonymous entities is a significant issue in such environments. The distributed entities establish connections to interact with others, which may include selfish and misbehaving entities and result in bad experiences. Therefore, trustworthiness evaluation using trust management techniques has become a significant issue in securing these environments to allow entities decide on the reliability and trustworthiness of other entities, besides it helps coping with defection problems and stimulating entities to cooperate. Recent models on evaluating trustworthiness in distributed systems have heavily focused on assessing trustworthiness of entities and isolate misbehaviours based on single trust metrics. Less effort has been put on the investigation of the subjective nature and differences in the way trustworthiness is perceived to produce a composite multidimensional trust metrics to overcome the limitation of considering single trust metric. In the light of this context, this thesis concerns the evaluation of entities’ trustworthiness by the design and investigation of trust metrics that are computed using multiple properties of trust and considering environment. Based on the concept of probabilistic theory of trust management technique, this thesis models trust systems and designs cooperation techniques to evaluate trustworthiness in mobile ad hoc networks (MANETs). A recommendation based trust model with multi-parameters filtering algorithm, and multidimensional metric based on social and QoS trust model are proposed to secure MANETs. Effectiveness of each of these models in evaluating trustworthiness and discovering misbehaving nodes prior to interactions, as well as their influence on the network performance has been investigated. The results of investigating both the trustworthiness evaluation and the network performance are promising. / Ministry of Higher Education in Libya and the Libyan Cultural Attaché bureau in London

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

<p dir="ltr">Federated Learning (FL), a novel subclass of Artificial Intelligence, decentralizes the learning process by enabling participants to benefit from a comprehensive model trained on a broader dataset without direct sharing of private data. This approach integrates multiple local models into a global model, mitigating the need for large individual datasets. However, the decentralized nature of FL increases its vulnerability to adversarial attacks. These include backdoor attacks, which subtly alter classification in some categories, and byzantine attacks, aimed at degrading the overall model accuracy. Detecting and defending against such attacks is challenging, as adversaries can participate in the system, masquerading as benign contributors. This thesis provides an extensive analysis of the various security attacks, highlighting the distinct elements of each and the inherent vulnerabilities of FL that facilitate these attacks. The focus is primarily on backdoor attacks, which are stealthier and more difficult to detect compared to byzantine attacks. We explore defense strategies effective in identifying malicious participants or mitigating attack impacts on the global model. The primary aim of this research is to evaluate the effectiveness and limitations of existing server-level defenses and to develop innovative defense mechanisms under diverse threat models. This includes scenarios where the server collaborates with clients to thwart attacks, cases where the server remains passive but benign, and situations where no server is present, requiring clients to independently minimize and isolate attacks while enhancing main task performance. Throughout, we ensure that the interventions do not compromise the performance of both global and local models. The research predominantly utilizes 2D and 3D datasets to underscore the practical implications and effectiveness of proposed methodologies.</p>