This thesis introduces a new methodology for energy estimation in asynchronous circuits. Unlike existing probabilistic methods, this is the first simulative work for energy estimation in all types of asynchronous circuits. The new simulative methodology is based on Petri net modeling. A real delay model is incorporated to capture both gate delays and interconnect delays. The switching activity at each gate is captured to measure the average dynamic energy consumed per request/acknowledge handshaking pair. The new type of Petri net is called Hierarchical Colored Asynchronous Hardware Petri net (HCAHPN). The HCAHPN is able to capture the temporal and spatial correlations of signals within a circuit, while preserving gate logic behavior and timing information. While Petri nets have been previously used for simulating combinational and sequential circuits, this is the first work that uses Petri nets for simulating asynchronous circuits. While different asynchronous design styles make various assumptions on the gate and wire delays present with the circuit, the physical implementations of these circuits always have gate and interconnect delays. Unlike previous methods, the proposed methodology is independent of the asynchronous design style used and it can be adapted for all types of asynchronous circuits that use handshaking communication.

Há três décadas, os sistemas de informação corporativos eram projetados para apoiar a execução de tarefas pontuais. Atualmente, esses sistemas também precisam gerenciar os fluxos de trabalho (workflows) e processos de negócio de uma organização. Em comunidades científicas de físicos, astrônomos, biólogos, geólogos, entre outras, seus sistemas de informações distinguem-se dos existentes em ambientes corporativos por: tarefas repetitivas (como re-execução de um mesmo experimento), processamento de dados brutos em resultados adequados para publicação; e controle de condução de experimentos em diferentes ambientes de hardware e software. As diferentes características dos dois ambientes corporativo e científico propiciam que ferramentas e formalismos existentes ou priorizem o controle de fluxo de tarefas, ou o controle de fluxo de dados. Entretanto, há situações em que é preciso atender simultaneamente ao controle de transferência de dados e ao controle de fluxo de tarefas. Este trabalho visa caracterizar e delimitar o controle e representação do fluxo de dados em processos de negócios e workflows científicos. Para isso, são comparadas as ferramentas CPN Tools e KEPLER, que estão fundamentadas em dois formalismos: redes de Petri coloridas e grafos de workflow orientados a atores, respectivamente. A comparação é feita por meio de implementações de casos práticos, usando os padrões de controle de dados como base de comparação entre as ferramentas. / Three decades ago, business information systems were designed to support the execution of individual tasks. Todays information systems also need to support the organizational workflows and business processes. In scientific communities composed by physicists, astronomers, biologists, geologists, among others, information systems have different characteristics from those existing in business environments, like: repetitive procedures (such as re-execution of an experiment), transforming raw data into publishable results; and coordinating the execution of experiments in several different software and hardware environments. The different characteristics of business and scientific environments propitiate the existence of tools and formalisms that emphasize control-flow or dataflow. However, there are situations where we must simultaneously handle the data transfer and control-flow. This work aims to characterize and define the dataflow representation and control in business processes and scientific workflows. In order to achieve this, two tools are being compared: CPN Tools and KEPLER, which are based in the formalisms: colored Petri nets and actors-oriented workflow graphs, respectively. The comparison will be done through implementation of practical cases, using the dataflow patterns as comparison basis.

Há três décadas, os sistemas de informação corporativos eram projetados para apoiar a execução de tarefas pontuais. Atualmente, esses sistemas também precisam gerenciar os fluxos de trabalho (workflows) e processos de negócio de uma organização. Em comunidades científicas de físicos, astrônomos, biólogos, geólogos, entre outras, seus sistemas de informações distinguem-se dos existentes em ambientes corporativos por: tarefas repetitivas (como re-execução de um mesmo experimento), processamento de dados brutos em resultados adequados para publicação; e controle de condução de experimentos em diferentes ambientes de hardware e software. As diferentes características dos dois ambientes corporativo e científico propiciam que ferramentas e formalismos existentes ou priorizem o controle de fluxo de tarefas, ou o controle de fluxo de dados. Entretanto, há situações em que é preciso atender simultaneamente ao controle de transferência de dados e ao controle de fluxo de tarefas. Este trabalho visa caracterizar e delimitar o controle e representação do fluxo de dados em processos de negócios e workflows científicos. Para isso, são comparadas as ferramentas CPN Tools e KEPLER, que estão fundamentadas em dois formalismos: redes de Petri coloridas e grafos de workflow orientados a atores, respectivamente. A comparação é feita por meio de implementações de casos práticos, usando os padrões de controle de dados como base de comparação entre as ferramentas. / Three decades ago, business information systems were designed to support the execution of individual tasks. Todays information systems also need to support the organizational workflows and business processes. In scientific communities composed by physicists, astronomers, biologists, geologists, among others, information systems have different characteristics from those existing in business environments, like: repetitive procedures (such as re-execution of an experiment), transforming raw data into publishable results; and coordinating the execution of experiments in several different software and hardware environments. The different characteristics of business and scientific environments propitiate the existence of tools and formalisms that emphasize control-flow or dataflow. However, there are situations where we must simultaneously handle the data transfer and control-flow. This work aims to characterize and define the dataflow representation and control in business processes and scientific workflows. In order to achieve this, two tools are being compared: CPN Tools and KEPLER, which are based in the formalisms: colored Petri nets and actors-oriented workflow graphs, respectively. The comparison will be done through implementation of practical cases, using the dataflow patterns as comparison basis.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Denial-of-service attacks (DoS) and distributed denial-of-service attacks (DDoS) attempt to temporarily disrupt users or computer resources to cause service un- availability to legitimate users in the internetworking system. The most common type of DoS attack occurs when adversaries °ood a large amount of bogus data to interfere or disrupt the service on the server. The attack can be either a single-source attack, which originates at only one host, or a multi-source attack, in which multiple hosts coordinate to °ood a large number of packets to the server. Cryptographic mechanisms in authentication schemes are an example ap- proach to help the server to validate malicious tra±c. Since authentication in key establishment protocols requires the veri¯er to spend some resources before successfully detecting the bogus messages, adversaries might be able to exploit this °aw to mount an attack to overwhelm the server resources. The attacker is able to perform this kind of attack because many key establishment protocols incorporate strong authentication at the beginning phase before they can iden- tify the attacks. This is an example of DoS threats in most key establishment protocols because they have been implemented to support con¯dentiality and data integrity, but do not carefully consider other security objectives, such as availability. The main objective of this research is to design denial-of-service resistant mechanisms in key establishment protocols. In particular, we focus on the design of cryptographic protocols related to key establishment protocols that implement client puzzles to protect the server against resource exhaustion attacks. Another objective is to extend formal analysis techniques to include DoS- resistance. Basically, the formal analysis approach is used not only to analyse and verify the security of a cryptographic scheme carefully but also to help in the design stage of new protocols with a high level of security guarantee. In this research, we focus on an analysis technique of Meadows' cost-based framework, and we implement DoS-resistant model using Coloured Petri Nets. Meadows' cost-based framework is directly proposed to assess denial-of-service vulnerabil- ities in the cryptographic protocols using mathematical proof, while Coloured Petri Nets is used to model and verify the communication protocols using inter- active simulations. In addition, Coloured Petri Nets are able to help the protocol designer to clarify and reduce some inconsistency of the protocol speci¯cation. Therefore, the second objective of this research is to explore vulnerabilities in existing DoS-resistant protocols, as well as extend a formal analysis approach to our new framework for improving DoS-resistance and evaluating the performance of the new proposed mechanism. In summary, the speci¯c outcomes of this research include following results; 1. A taxonomy of denial-of-service resistant strategies and techniques used in key establishment protocols; 2. A critical analysis of existing DoS-resistant key exchange and key estab- lishment protocols; 3. An implementation of Meadows's cost-based framework using Coloured Petri Nets for modelling and evaluating DoS-resistant protocols; and 4. A development of new e±cient and practical DoS-resistant mechanisms to improve the resistance to denial-of-service attacks in key establishment protocols.

Dentre as várias abordagens consagradas para análise de desempenho de algoritmos em termos de tempo de execução, destacam-se, por exemplo, a análise assintótica, as técnicas de recorrências e a análise probabilística. Entretanto, há algoritmos que apresentam certas peculiaridades que tornam o uso dessas técnicas puramente matemáticas de avaliação de desempenho inadequadas ou excessivamente árduas. É o caso, por exemplo, de algoritmos cujo tempo de execução pode variar significativamente para um mesmo dado de entrada em função da dinâmica de execução. O mesmo acontece no caso de algoritmos distribuídos em que, dependendo da complexidade da política de distribuição utilizada, a avaliação por meio de métodos analíticos do efeito de um gradual incremento de processadores no seu tempo de execução pode tornar-se impraticável. Em situações como essas, a fim de evitar a alta complexidade matemática envolvida na análise de desempenho desses algoritmos, algumas alternativas baseadas em métodos empíricos ou em modelagem visual vêm sendo adotada pelos pesquisadores. Contudo, ambas alternativas apresentam inconvenientes: no caso dos métodos empíricos, eles requerem a implementação dos algoritmos analisados, o que tem um efeito perverso particularmente no caso dos algoritmos distribuídos, uma vez que eles demandam a aquisição prévia de recursos de hardware dispendiosos de multi-processamento antes mesmo de saber se a proposta de distribuição investigada, de fato, vale a pena. Já as abordagens baseadas em modelos visuais atualmente utilizadas (baseadas em grafos, autômatos e Unified Modeling Language - UML) não contam com os recursos dinâmicos necessários para lidar com a avaliação do tempo de execução dos algoritmos. Neste cenário, o presente trabalho propõe uma abordagem visual formal para avaliar o tempo de execução de algoritmos baseada em simulações automáticas de modelos de Redes de Petri Coloridas Hierárquicas (RdPCH) no ambiente gráfico CPN Tools. A abordagem proposta é validada por meio de cálculo dos seguintes parâmetros associados aos algoritmos usados como estudo de caso: a função de complexidade, o tempo de execução real e, no caso dos algoritmos distribuídos, o speedup e a eficiência. Foram usados como estudos de caso os seguintes três relevantes algoritmos de busca usados nos agentes da Inteligência Artificial com a finalidade de definir as ações mais apropriadas que tais agentes devem executar de modo a cumprir seu objetivo, com êxito, em um ambiente em que um oponente tenta minimizar suas chances de sucesso: os algoritmos seriais Minimax e Alpha-Beta; e o algoritmo distribuído PVS. Os resultados obtidos confirmam a correção da abordagem proposta. / Among the various approaches established for analyzing the performance of algorithms in terms of runtime, one can highlight as examples, the asymptotic analysis, recurrence techniques, and probabilistic analysis. However, there are algorithms that present certain peculiarities, which make the use of these purely mathematical performance evaluation techniques inadequate or excessively difficult. This is the case of algorithms for which the runtime varies significantly for the same input data, due to its execution dynamics. The same happens in the case of distributed algorithms, where depending on the complexity of the distribution policy being used, the evaluation by means of analytical methods concerning the effect of a gradual increase in processors on runtime can become impractical. In situations such as these, in order to avoid the high mathematical complexity involved in the performance analysis, researchers have adopted alternatives based on empirical methods or visual modeling. However, both alternatives have drawbacks: in the case of empirical methods, they require the implementation of analyzed algorithms, which has a perverse effect especially in the case of distributed algorithms. This occurs, as they demand the acquisition beforehand of expensive multiprocessing hardware resources before knowing if the distribution proposal under investigation is in fact viable. On the other hand, those approaches based on visual models currently under use (based on graphs, automata and Unified Modeling Language) one notes that does not contain the necessary dynamic resources for dealing with the runtime evaluation of algorithms. In this scenario, the present study proposes a formal visual approach, in order to evaluate the algorithm runtime based on automatic simulations of Hierarchical Colored Petri Net models in the CPN Tools graphic environment. The proposed approach is validated through the calculation of the following parameters associated with the algorithms being used as a case study: the complexity function, real runtime, and in the case of distributed algorithms, speedup and efficiency. The cases studies were based on three relevant search algorithms used in the agents of the Artificial Intelligence, with the aim of defining the most appropriate actions that these agents need to execute in order to fulfil their objective, in an environment where the opponent tries to minimize their chances of success. The algorithms under consideration were the serial algorithms Minimax and Alpha-Beta; and the PVS distributed algorithm. The obtained results confirm the correction of the proposed approach. / Tese (Doutorado)

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / This work presents a method to generate games with multilevel and multiple users using Hierarchical Coloured Petri Nets. The design of a multiuser game containing multiple navigation environments (multilevel) is made from the model of a Hierarchical Coloured Petri Net, in which are specified all of the rules, properties and structures of the game. The created model for the game can be formally analysed, verifying the existence of deadlocks and invalid paths, for example, and others possible conception problems, that can be done with the tools available on CPN Tools. To validate this method, a tool has been developed, called CPN Games, which allows fast and dynamic development of simple conception games only using Hierarchical Coloured Petri Nets. The XML codes of the designed models in CPN Tools are interpreted by CPN Games following a set of predefined rules to instantiate different games, without additional programing. It is demonstrated the mechanisms of the design, analysis and validation of the models and finally it is presented several examples of games developed by this tool. / Este trabalho apresenta um mÃtodo para geraÃÃo de jogos multinÃveis e com mÃltiplos usuÃrios por meio de modelagem em Redes de Petri Coloridas HierÃrquicas. A concepÃÃo de um jogo multiusuÃrio, contendo mÃltiplos ambientes de navegaÃÃo (multinÃveis), à feita a partir da criaÃÃo de um modelo hierÃrquico em Rede de Petri Colorida, no qual se especificam todas as regras, propriedades e estruturas do jogo. O modelo criado para o jogo pode ser analisado formalmente, verificando-se, por exemplo, a existÃncia de bloqueios e de transiÃÃes mortas (caminhos invÃlidos), entre outros possÃveis problemas de concepÃÃo, o que pode ser feito com a utilizaÃÃo de ferramentas disponÃveis no CPN Tools. Para validar esse mÃtodo, foi concebida uma ferramenta, denominada CPN Games, que permite o desenvolvimento rÃpido e dinÃmico de jogos de concepÃÃo simples exclusivamente por Rede de Petri Colorida HierÃrquica. Os cÃdigos em XML de modelos constituÃdos com o CPN Tools sÃo interpretadas pelo CPN Games seguindo um conjunto de regras prà estabelecidas para instanciar diferentes jogos, sem a necessidade de programaÃÃo adicional. SÃo demonstrados os mecanismos de criaÃÃo, anÃlise e validaÃÃo dos modelos e diferentes exemplos de jogos construÃdos com a ferramenta.