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The availability of numerous mobile agent systems with its own strengths and weaknesses poses a problem when deciding on a particular mobile agent system. In this dissertation, factors based on mobility, communication and security of the mobile agent systems are presented and used as a means to address this problem. To facilitate in the process of selection, a grouping scheme of the agent system was proposed. Based on this grouping scheme, mobile agent systems with common properties are grouped together and analyzed against the above-mentioned factors. In addition, an application was developed using the Aglet Software Development Toolkit to demonstrate certain features of agent mobility, communication and security. / Theoretical Computing / M. Sc. (Computer Science)

The availability of numerous mobile agent systems with its own strengths and weaknesses poses a problem when deciding on a particular mobile agent system. In this dissertation, factors based on mobility, communication and security of the mobile agent systems are presented and used as a means to address this problem. To facilitate in the process of selection, a grouping scheme of the agent system was proposed. Based on this grouping scheme, mobile agent systems with common properties are grouped together and analyzed against the above-mentioned factors. In addition, an application was developed using the Aglet Software Development Toolkit to demonstrate certain features of agent mobility, communication and security. / Theoretical Computing / M. Sc. (Computer Science)

Approved for public release, distribution is unlimited / The management of the battlefield network takes place in a Network Operations Center (NOC). The manager, based on the importance of the managed network, is sometimes required to be present all the time within the physical installations of the NOC. The decisions regard a wide spectrum of network configurations, fault detection and repair, and network performance improvement. Especially in the case of the battlefield network operations these decisions are sometimes so important that can be characterized as critical to the success of the whole military operation. Most of the times, the response time is so restricted that exceeds the mean physical human response limits. An automated response that also carries the characteristics of human intelligence is needed to overcome the restrictions the human nature of an administrator imposes. The research will establish the proper computer network management architecture for an adaptive network. This architecture will enhance the capabilities of network management and in terms of cost and efficiency. / Lieutenant Commander, Hellenic Navy

Em aplicações distribuídas baseadas em agentes móveis, a coordenação das ações dos agentes móveis é uma tarefa complexa. A maior dificuldade é devido ao fato que agentes móveis podem mudar de endereço dinamicamente. Nesta dissertação, apresentamos o projeto e a implementação de um mecanismo de coordenação de agentes móveis que contorna este problema. Este mecanismo, que chamamos de Canal de Broadcast, está baseado na difusão de mensagens e possibilita que os membros de um grupo de agentes móveis interajam entre si, independentemente de suas localizações correntes. Modelos de coordenação existentes oferecem formas de interação entre agentes móveis, mas todos eles impõem alguma exigência. Ou os agentes móveis devem conhecer a localização de outros agentes, ou devem estar localizados no mesmo lugar ou devem migrar para um lugar específico. A principal vantagem deste mecanismo de coordenação está na total transparência de localização: as mensagens podem ser endereçadas a um conjunto de agentes móveis independentemente de sua localização corrente. Este mecanismo foi implementado no ASDK (Aglets Software Development Kit) da IBM e a sua utilidade foi demonstrada usando dois problemas típicos de coordenação em Sistemas Distribuídos: a Exclusão Mútua e o protocolo Manager-Workers. Testamos o desempenho do mecanismo e identificamos que o custo do Canal de Broadcast não é tão alto comparado aos benefícios que proporciona. Através deste mecanismo, os agentes móveis poderão executar as suas tarefas e interagir entre sí com o propósito da coordenação sem as exigências impostas por outros modelos de coordenação. / In distributed applications based on mobile agents, the coordination of mobile agents actions is a difficult task. The main difficulty comes from the fact that mobile agents can change their address dynamically. In this dissertation, we present the project and implementation of a mechanism for coordinating mobile agents that overcomes this problem. This mechanism, which we called Broadcast Channel, is based on the difusion of messages and enables the members of a mobile agent group to interact with each other independently of their current locations. Existing coodination models offer some means of interaction between mobile agents, but all of them impose some requirements. Either the mobile agents must know about each other's location, or must be located at the same place or must move to a specific place. The main advantage of our coordination mechanism is the full location transparency: the messages can be sent to a set of mobile agents independently of their current locations. This mechanism was implemented using IBM's ASDK (Aglets Software Development Kit) and its use was demonstrated using two typical coordination problems in Distributed Systems: the Mutual Exclusion and the Manager-Workers protocol. We tested the performance of the mechanism and identified that the cost of the Broadcast Channel is not too high, compared to the benefit it provides. Through this mechanism, the mobile agents can do their tasks and interact with each other for the purpose of coordination without the requirements imposed by other models.

Récemment, l’informatique distribuée a connu une grande évolution en raison de l’utilisation du paradigme des agents mobiles, doté d’innovantes capacités, au lieu du système client-serveur où les applications sont liées à des nœuds particuliers dans les réseaux. Ayant capturé l’intérêt des chercheurs et de l’industrie, les agents mobiles sont capables de migrer de manière autonome d’un nœud à un autre à travers le réseau, en transférant de leur code et leurs données, ce qui leur permet d’effectuer efficacement des calculs, de recueillir des informations et d’accomplir des tâches. Cependant, en dépit de ses avantages significatifs, ce paradigme souffre encore de certaines limitations qui font obstacle à son expansion, principalement dans le domaine de la sécurité. Selon les efforts actuellement déployés pour évaluer la sécurité des agents mobiles, deux catégories de menaces sont considérées. La première catégorie concerne les attaques menées sur l’agent mobile lors de son voyage à travers des hôtes ou des entités malveillantes, tandis que la seconde catégorie traite les attaques effectuées par un agent mobile illicite afin d’affecter la plate-forme d’hébergement et de consommer ses ressources. Ainsi, il est substantiellement nécessaire de concevoir une infrastructure de sécurité complète pour les systèmes d’agents mobiles, qui comprend la méthodologie, les techniques et la validation. L’objectif de cette thèse est de proposer des approches qui fournissent cette technologie avec des fonctionnalités de sécurité, qui correspondent à sa structure globale sans compromettre ses capacités de mobilité, l’interopérabilité et l’autonomie. Notre première approche est basée sur la sérialisation XML et des primitives cryptographiques, afin d’assurer une mobilité persistante de l’agent ainsi qu’une communication sécurisée avec les plates-formes d’hébergement. Dans la seconde approche, nous avons conçu une alternative à la première approche en utilisant la sérialisation binaire et la cryptographie à base de l’identité. Notre troisième approche introduit l’aspect d’anonymat à l’agent mobile, et lui fournit un mécanisme de traçage pour détecter les intrusions le long de son voyage. La quatrième approche a été développée dans le but de restreindre l’accès aux ressources de la plate-forme de l’agent, en utilisant une politique de contrôle d’accès bien définie à base la cryptographie à seuil. A ce stade, on s’est intéressé à expérimenter l’utilité des agents mobiles avec des fonctionnalités de sécurité, dans la préservation de la sécurité des autres technologies, telles que le Cloud Computing. Ainsi, nous avons proposé une architecture innovante du Cloud, en utilisant des agents mobiles dotés de traces cryptographiques pour la détection d’intrusion et d’un protocole de révocation à base de seuil de confiance pour la prévention. / Recently, the distributed computing has witnessed a great evolution due to the use of mobile agent paradigm, endowed with innovative capabilities, instead of the client-server system where the applications are bound to particular nodes in networks. Having captured the interest of researchers and industry, the mobile agents areable to autonomously migrate from one node to another across the network, transferring their code and data, which allows them to efficiently perform computations, gather information and accomplish tasks. However, despite its significant benefits, this paradigm still suffering from some limitations that obstruct its expansion, primarily in the area of security. According to the current efforts to investigate the security of mobile agents, two categories of threats are considered. The first one concerns the attacks carried out on the mobile agent during its travel or stay by malicious hosts or entities, while the second one deals the attacks performed by a malicious mobile agent in order to affect the hosting platform and consume its resources. Thus, it is substantially needed to conceive a complete security infrastructure for mobile agent systems, which includes methodology, techniques and validation. The aim of this thesis is to propose approaches which provide this technology with security features, that meet with its overall structure without compromising its mobility, interoperbility and autonomy capabilities. Our first approach was based on XML serialization and cryptographic primitives, in order to ensure a persistent mobility of agent as well as a secure communication with hosting platforms. In the second approach, we have conceived an alternative to the first approach using binary serialization and Identity-based cryptography. Our third approach was proposed to introduce anonymity aspect to the mobile agent, and provide him with a tracing mechanism to detect intrusions along its trip. The fourth approach was developed in order to restrict the access to the resources of the agent platform, using a well-defined access control policy based on threshold cryptography. At this stage, we find it interesting to experiment the utility of mobile agents with security features in preserving the security of other technologies such as cloud computing. Thus, we have developed an innovative cloud architecture using mobile agents endowed with cryptographic traces for intrusion detection and a revocation protocol based on trust threshold for prevention.

In this thesis we look at mobile agent solutions to black hole search and related problems. Mobile agents are computational entities that are autonomous, mobile, and can interact with their environment and each other. The black hole search problem is for a team of these agents to work together to map or explore a graph-like network environment where some elements of the network are dangerous to the agents. Most research into black hole search has focussed on finding a single dangerous node: a black hole. We look at the problem of finding multiple black holes and, in the case of dangerous graph exploration, multiple black links as well. We look at the dangerous graph exploration problem in the network model. The network model is based on a normal static computer network modelled as a simple graph. We give an optimal solution to the dangerous graph exploration problem using agents that start scattered on nodes throughout the network. We then make the problem more difficult by allowing an adversary to delete links during the execution of the algorithm and provide a solution using scattered agents. In the last decade or two, types of networks have emerged, such as ad hoc wireless networks, that are by their nature dynamic. These networks change quickly over time and can make distributed computations difficult. We look at black hole search in one type of dynamic network described by the subway model, which we base on urban subway systems. The model allows us to look at the cost of opportunistic movement by requiring the agents to move using carriers that follow routes among the network's sites, some of which are black holes. We show that there are basic limitations on any solution to black hole search in the subway model and prove lower bounds on any solution's complexity. We then provide two optimal solutions that differ in the agents' starting locations and how they communicate with one another. Our results provide a small window into the cost of deterministic distributed computing in networks that have dynamic elements, but which are not fully random.

In this thesis we look at mobile agent solutions to black hole search and related problems. Mobile agents are computational entities that are autonomous, mobile, and can interact with their environment and each other. The black hole search problem is for a team of these agents to work together to map or explore a graph-like network environment where some elements of the network are dangerous to the agents. Most research into black hole search has focussed on finding a single dangerous node: a black hole. We look at the problem of finding multiple black holes and, in the case of dangerous graph exploration, multiple black links as well. We look at the dangerous graph exploration problem in the network model. The network model is based on a normal static computer network modelled as a simple graph. We give an optimal solution to the dangerous graph exploration problem using agents that start scattered on nodes throughout the network. We then make the problem more difficult by allowing an adversary to delete links during the execution of the algorithm and provide a solution using scattered agents. In the last decade or two, types of networks have emerged, such as ad hoc wireless networks, that are by their nature dynamic. These networks change quickly over time and can make distributed computations difficult. We look at black hole search in one type of dynamic network described by the subway model, which we base on urban subway systems. The model allows us to look at the cost of opportunistic movement by requiring the agents to move using carriers that follow routes among the network's sites, some of which are black holes. We show that there are basic limitations on any solution to black hole search in the subway model and prove lower bounds on any solution's complexity. We then provide two optimal solutions that differ in the agents' starting locations and how they communicate with one another. Our results provide a small window into the cost of deterministic distributed computing in networks that have dynamic elements, but which are not fully random.