Le Cloud Computing est de plus en plus reconnu comme une nouvelle façon d'utiliser, à la demande, les services de calcul, de stockage et de réseau d'une manière transparente et efficace. Dans cette thèse, nous abordons le problème d'ordonnancement de workflows sur les infrastructures distribuées hétérogènes du Cloud Computing. Les approches d'ordonnancement de workflows existantes dans le Cloud se concentrent principalement sur l'optimisation biobjectif du makespan et du coût. Dans cette thèse, nous proposons des algorithmes d'ordonnancement de workflows basés sur des métaheuristiques. Nos algorithmes sont capables de gérer plus de deux métriques de QoS (Quality of Service), notamment, le makespan, le coût, la fiabilité, la disponibilité et l'énergie dans le cas de ressources physiques. En outre, ils traitent plusieurs contraintes selon les exigences spécifiées dans le SLA (Service Level Agreement). Nos algorithmes ont été évalués par simulation en utilisant (1) comme applications: des workflows synthétiques et des workflows scientifiques issues du monde réel ayant des structures différentes; (2) et comme ressources Cloud: les caractéristiques des services de Amazon EC2. Les résultats obtenus montrent l'efficacité de nos algorithmes pour le traitement de plusieurs QoS. Nos algorithmes génèrent une ou plusieurs solutions dont certaines surpassent la solution de l'heuristique HEFT sur toutes les QoS considérées, y compris le makespan pour lequel HEFT est censé donner de bons résultats. / Cloud Computing is increasingly recognized as a new way to use on-demand, computing, storage and network services in a transparent and efficient way. In this thesis, we address the problem of workflows scheduling on distributed heterogeneous infrastructure of Cloud Computing. The existing workflows scheduling approaches mainly focus on the bi-objective optimization of the makespan and the cost. In this thesis, we propose news workflows scheduling algorithms based on metaheuristics. Our algorithms are able to handle more than two QoS (Quality of Service) metrics, namely, makespan, cost, reliability, availability and energy in the case of physical resources. In addition, they address several constraints according to the specified requirements in the SLA (Service Level Agreement). Our algorithms have been evaluated by simulations. We used (1) synthetic workflows and real world scientific workflows having different structures, for our applications; and (2) the features of Amazon EC2 services for our Cloud. The obtained results show the effectiveness of our algorithms when dealing multiple QoS metrics. Our algorithms produce one or more solutions which some of them outperform the solution produced by HEFT heuristic over all the QoS considered, including the makespan for which HEFT is supposed to give good results.

Le développement orienté-service et le cloud computing offrent beaucoup d'opportunités au développement et au déploiement d'applications. En effet, le développement orienté-service permet de composer des fonctionnalités issues de services distribués, développés par différentes organisations. D'un autre côté, le cloud computing permet de provisionner des environnements évolutifs (en fonction du besoin en ressources) de développement et de déploiement, à la demande. Dans ce travail de recherche, nous proposons et décrivons une méthode de provisonnement automatique d'applications métier, orientées-service sur le cloud. Nous avons appelé cette méthode MADONA (Method for AutomateD prOvisioning of service-oriented busiNess Applications). MADONA couvre le cycle de vie de provisionnement d'applications et est basée sur un orchestrateur de services pour la gestion de la configuration, du déploiement, et de la composition de services métier.Dans ce travail, nous visons à réduire les connaissances techniques nécessaires au provisionnement d'applications métier. Pour ce faire, nous apportons trois contributions majeures. Premièrement, l'automatisation de ce provisionnement. En effet, les phases de MADONA sont complètement automatisées. L'utilisateur n'intervient que pour exprimer son besoin et pour utiliser l'application métier automatiquement générée (par la composition de services métier) et déployée sur une IaaS présélectionnée. Deuxièmement, l'enrichissement de la description des services par des concepts liés aux relations d'un service. En effet, les langages de description de services décrivent le plus souvent ces derniers comme des entités isolées et ne considèrent pas les relations entre services. Nous avons défini dans ce travail les relations de composition qui décrivent pour chaque service métier les services nécessaires à son bon fonctionnement, et les services avec lesquels il peut être composé.Troisièmement, nous permettons à l'utilisateur d'exprimer son besoin à un haut niveau d'abstraction des détails techniques de composition et de déploiement. Nous avons pour cela défini un vocabulaire pour formaliser ces besoins fonctionnels (en termes de mots clés décrivant les fonctionnalités désirées, ou de noms de services désirés) et non fonctionnels (en termes de coût, de préférences de déploiement (ex : localisation de déploiement), et de qualité de service). La méthode a été prototypée et testée suivant plusieurs scénarios montrant sa faisabilité / Service-oriented computing and cloud computing offer many opportunities for developing and deploying applications. In fact, service-oriented computing allows to compose several functionalities from distributed services developed by different organizations. On the other hand, cloud computing allows to provision on demand scalable development and deployment environments. In this resarch work, we propose and describe a Method for AutomateD prOvisioning of service-oriented cloud busiNess Applications (MADONA). The method covers the whole application’s lifecycle and is based on cloud orchestration tools that manage the deployment and dependencies of supplied components. This research work aims to reduce the necessary technical knowledge for provisioning service-oriented cloud applications. To this end, we bring three major contributions. Firstly, we automatise the whole application provisioning. In fact, MADONA phases are fully automated. The user intervenes only in requirement elicitation and when the application is deployed and ready to use. The business application is automatically generated (by composing business services) and deployed in an automatically preselected IaaS. Secondly, we enrich the description of services by integrating concepts describing services’ interactions. In fact, service description languages usually describe services as isolated components and does not consider the interactions between services. We define in this work, composition interactions which describe for each business service, its necessary services and the services with which it can be composed. Thirdly, we allow the user to express her requirements abstracting composition and deployment technical details. To this end, we defined a RequIrement VocAbuLary (RIVAL) to formalize user’s functional (in terms of keywords describing the desired functionalities, or names of desired services) and non-functional requirements (in terms of cost, deployment preferences (ex. preferred location), and quality of service). The method has been implemented and tested showing its faisability

I takt med att världen digitaliseras och att allt fler företag börjar upptäcka fördelarna med molnbaserade IT-system, så misslyckas fortfarande hela 2/3 av alla IT-projekt trots att liknande projekt har gjorts många gånger förut. Denna kandidatuppsats har som syfte identifiera, beskriva och förklara de faktorer som påverkar en övergång från dagens lokalt lagrade system till molnbaserade IT-system, ur kund-, projektgrupp- och systemimplementatörsperspektiv. Primära empiriska data har samlats in genom kvalitativa intervjuer av fyra respondenter. Intervju-erna fokuserade på deras erfarenheter och uppfattningar om vilka faktorer som påverkar en övergång från lokalt lagrade system till molnbaserade IT-system. Respondenterna har olika perspektiv och har olika arbetsbakgrund, men gemensamt är att samtliga arbetar inom IT-området. Tre av dem har syste-mimplementatörsbakgrund och den fjärde arbetar som IT-chef hos ett kundföretag. En viktig slutsats från denna studie är att det inte finns lika stora risker vid en övergång till ett molnbaserat IT-system som marknaden upplever. De faktorer som har en hög påverkan på en fram-gångsrik övergång från lokalt till molnbaserade IT-system, Ur ett systemimplementatörsperspektiv är det individen och den individuella förmågan och kompetens. Ur ett projektgruppperspektiv är det att etablera en effektiv kommunikation.  Ur ett kundperspektiv är deras mognad och samsyn för projektet

Technology that is widely discussed in the business community today is cloud computing and cloud-based systems, as a cloud-based CRM-system. Considering that large companies, such as Google, Netflix and Microsoft, use this type of technology, it is important to ask whether such systems add something to the business or whether it is just an IT trend. The purpose of this study is therefore to create a decision model that will determine whether the company will implement a cloud-based system or maintain it in on-premises. The decision model should shed light on various criteria for cloud-based solutions. The study will be designed with the help of the TOE framework (technology, organization and environment). The aim of the study is to answer the following research questions: (1) What are the consequences and benefits of cloud-based systems? (2) what are the differences between the criteria in the literature compare to what you  practice? (3) Are there differences in the views of the supplier and the customer around this area? The result is based on qualitative interviews with people from the supplier and the customer. The interviews also represent the TOE framework. In addition, an interview with an external expert has been carried out in order to evaluate and support the results of the conducted interviews. The survey has resulted in a decision model with three alternatives and eleven criterias. The analysis shows that there is a difference in what the literature emphasizes compared to what you actually are doing.  The views between the supplier and the customer are also different. Where the customer does not want to lose control and experience a lock-in effect. On the other hand, the supplier wants to deliver the latest technology and give new challenges to their employees. The study can be concluded as follows: the main reason for not implementing the cloud-based system for the customer is; deposit, cost and loss of control. The main reason for implementing the cloud-based system for the vendor is; consultant development, functionality and availability. / Teknologi er altomfattende og oppslukende. Teknologiutvikling aksele-rerer raskere hver eneste dag, og kan raskt bidra til å skape et skille mellom de aktører som følger utviklingen og de som uteblir fra utvik-lingen.  Tilfører cloudbaserte og cloud computing nytte til bedriften eller er det kun en IT-trend? Hensikten med dette studiet er derfor å skape en beslutningsmodell som skal avgjøre om bedriften skal implementere et cloudbasert system eller bevare de systemer de har i dag i et  on-premises miljø. Beslutningsmodellen skal belyse ulike kriterier innen cloudbaserte løsninger. Studien skal utformes med hjelp av TOE-rammeverket (teknologi, organisasjon og miljø). Målet med studien er å besvare følgende forskningsspørsmål: (1) hvilke konsekvenser og nytteverdier medfører cloudbaserte systemer? (2) hvilke forskjeller er det mellom kriteriene i litteraturen og det som utføres i praksis? (3) finns det forskjeller på synspunktene til leverandøren og kunden rundt dette fagområdet? Resultatet bygger på kvalitative intervjuer med personer fra leverandøren av tjenesten og kunden. I tillegg har det blitt gjennom-ført et intervju med en ekstern ekspert, for å evaluere og støtte opp under resultatet fra gjennomførte  intervjuer. Undersøkelsen har resul-tert i en beslutningsmodell med to alternativ og elleve kriterier. Analy-sen viser at det er forskjeller  på hvilke kriterier litteraturen vektlegger sammenlignet med de kriterier som benyttes i praksis. Det er også forskjeller mellom de synspunkter som mellom leverandøren utrykker sammenlignet med og kundens synspunkter. Kunden ønsker ikke  å miste kontrollen og opplever en innlåsingseffekt. Leverandøren derimot ønsker å levere den nyeste teknologien samt bidra til økt stimulering gjennom effektivisering av arbeidsprosesser og rutiner. Dette bidrar til å stimulere og utfordre den enkelte ansatte.  Studien kan konkluderes på følgende måte: hovedårsaken for å ikke implementere cloudbaserte system for kunden er; innlåsing, investering og driftskostnad og risiko for tap av kontroll. Hovedårsaken  for å implementere et cloudbaserte system for leverandøren er; organisasjonens mulighet til å jobbe med nyeste teknologi stimulerer til økt konsulent utvikling, funksjonalitet og tilgjengelighet.

L'expansion des services en ligne, l'avènement du big data, favorisé par l'internet des objets et les terminaux mobiles, a entraîné une croissance exponentielle du nombre de centres de données qui fournissent des divers services de cloud computing. Par conséquent, la topologie du centre de données est considérée comme un facteur d'influence sur la performance du centre de données. En effet, les topologies des centres de données devraient offrir une latence faible, une longueur de chemin moyenne réduite avec une bande passante élevée. Ces exigences augmentent la consommation énergétique dans les centres de données. Dans cette dissertation, différentes solutions ont été proposées pour surmonter ces problèmes. Tout d'abord, nous proposons une nouvelle topologie appelée LCT (Linked Cluster Topology) qui augmente le nombre de nœuds, améliore la connexion réseau et optimise le routage des données pour avoir une faible latence réseau. Une nouvelle topologie appelée VacoNet (Variable connexion Network) a été également présentée. VacoNet offre un nouveau algorithme qui définit le exact nombre de port par commutateur pour connecter le nombre de serveurs requis tout en réduisant l'énergie consommée et les matériaux inutilisés (câbles, commutateurs). En outre, nous _étudions une nouvelle technique pour optimiser la consumation d'énergie aux centres de données. Cette technique peut périodiquement estimer la matrice de trafic et gérer l'_état des ports de serveurs tout en maintenant le centre de données entièrement connecté. La technique proposée prend en considération le trafic réseau dans la décision de gestion des ports. / Data centers (DC) are being built around the world to provide various cloud computing services. One of the fundamental challenges of existing DC is to design a network that interconnects massive number of nodes (servers)1 while reducing DC' cost and energy consumption. Several solutions have been proposed (e.g. FatTree, DCell and BCube), but they either scale too fast (i.e., double exponentially) or too slow. Effcient DC topologies should incorporate high scalability, low latency, low Average Path Length (APL), high Aggregated Bottleneck Throughput (ABT) and low cost and energy consumption. Therefore, in this dissertation, different solutions have been proposed to overcome these problems. First, we propose a novel DC topology called LCT (Linked Cluster Topology) as a new solution for building scalable and cost effective DC networking infrastructures. The proposed topology reduces the number of redundant connections between clusters of nodes, while increasing the numbers of nodes without affecting the network bisection bandwidth. Furthermore, in order to reduce the DCs cost and energy consumption, we propose first a new static energy saving topology called VacoNet (Variable Connection Network) that connects the needed number of servers while reducing the unused materials (cables, switches). Also, we propose a new approach that exploits the correlation in time of internode communication and some topological features to maximize energy saving without too much impacting the average path length.

Esta tese de Doutorado tem como objetivo apresentar uma arquitetura para metaescalonamento verde com provisão de qualidade de serviço em uma nuvem privada denominada GreenMACC. Essa nova arquitetura oferece a automatização na escolha de políticas em quatro estágios de escalonamento de uma nuvem privada, permitindo cumprir a negociação que foi estabelecida com o usuário. Devido a essa função, é possível garantir que o GreenMACC se comporte seguindo os princípios da computação verde sem deixar de se preocupar com a qualidade do serviço. Nesta tese o GreenMACC é apresentado, detalhado, discutido, validado e avaliado. Com os resultados apresentados pode-se concluir que a arquitetura proposta mostrou-se consistente, permitindo a execução dos serviços requisitados com diversas políticas de escalonamento em todos os seus estágios. Além disso, demonstrou flexibilidade em receber novas políticas, com focos verde e de qualidade de serviço, e eficiência na escolha das políticas de escalonamento de acordo com a negociação feita com o usuário. / This PhD thesis aims to present an architecture for green metascheduling with provision of quality of service in a private cloud called GreenMACC. This new architecture offers the possibility of choosing automatically the four stage scheduling policies of a private cloud, allowing to reach the users negotiation. As a result of this function, it is possible to ensure that GreenMACCs behavior follows the green computing principles and also is worried about the quality of the service. In this thesis Green- MACC is presented, particularized, discussed, validated and evaluated. The results show that the proposed architecture is consistent, allowing the execution of the requested services considering various scheduling policies in the stages. Moreover, GreenMACC proves to be flexible as allows new policies, focusing on green and quality of service, and to be efficient as chooses the scheduling policies following the users negotiation.

近年來，雲端運算成為我國貿易商理想的電子商務模式。雲端運算基本概念為將資訊和資源集中存放在「雲」上，透過網路服務提供資源，幫助企業提升效率、降低運籌成本。然而，雲端運算的原理造成使用者將資訊存放在網路之某處，使用者無法直接控制其資料，進而衍生出資訊安全之疑慮。也因此，當企業決定是否導入雲端運算時，往往將資訊安全納入考量。若欲鼓勵我國貿易商導入雲端運算，分析資訊安全風險、了解如何管理這類風險，係有其必要性。 本研究主要目的，係為我國貿易商提供較清晰之雲端運算資訊安全分析，包含雲端運算可能之資訊安全風險，以及管理這些風險的方式。依本研究比較分析之結果，雲端運算資訊安全風險與其他電腦或網路產品、服務之資訊安全風險類似，並可透過技術、管理與法律以降低風險。然而資訊安全風險無法被完全去除，在此情況下，貿易商宜透過契約保障其資訊本身、以及相關權利。 / In recent years, cloud computing has become an ideal way for most Taiwanese trading companies to adopt e-commerce. The basic model of cloud computing is to provide resource in the form of internet service. By centralizing data and resource onto “the cloud”, cloud computing helps companies to improve efficiency with lower budget. However, this approach raises concern about information security, for users’ data will be stored in the internet, rather than being directly controlled by the users. Due to this fact, companies tend to take information security into consideration before moving to the cloud. To encourage Taiwanese trading companies, analyzing and learning how to manage the information security risks are rather necessary. This research aims to provide a clearer view of the information security to Taiwanese trading companies, including the possible information security risks and the ways to manage these risks. Through comparison and analysis, we conclude that the information security risks of cloud computing and of other computer or internet products or service are similar, and these risks can be reduced by technical methods, management and laws. However, these risks cannot be removed, and in this situation, trading companies are suggested to protect their data and their rights via contracts.

計算、儲存與傳輸技術自60年代就一直引領資通訊科技(Information and Communication Technology；ICT)產業的發展，隨著ICT技術不斷的創新與擴散，現今ICT產品已經廣泛溶入人類的經濟和社會生活中。近年來，ICT產業已成為全球最具活力、規模最大的產業之一。可預期的未來，資通訊科技將會是牽動全球經濟發展最重要的產業技術。 台灣資通訊產業製造鏈相當完整，但是在全球ICT產業供應鏈的分工體系中大部份偏重在專業代工領域。面臨代工利潤的下滑，台灣ICT代工產業的前景已亮起嚴重的警訊。台灣產業在提供雲端運算服務的起步較晚，雲端運算服務市場的後進者如何從以ICT代工產業的角色轉進高附加價值的雲端運算服務市場，探討雲端運算服務市場的先行領導者之策略佈局將是相關後進者值得研究的議題。本研究將從通訊科技及電腦技術的演進來探究ICT提供雲端運算服務的本質，並藉由分析提供雲端運算服務之市場領導廠的策略佈局，探討初入雲端運算產業的後進者可行的佈局方向。藉此，希望能有助於雲端運算產業後進者對雲端運算服務更進一步的理解，並有助於ICT代工相關業者能在既有的技術下釐定發展策略，朝高附加價值雲端運算服務的方向邁進。 此外，台灣ICT硬體代工產業多年來因專注於製造的專業，對買者需求面資訊的探討不多，亦較忽視對客戶的售後支援與服務等的專業。對雲端服務市場而言，買者的需求是業者能否提供完善雲端服務的最重要資訊。對提供雲端服務者而言，目前企業大多已疲於追求外顯成本的效益（Cost Down），對於釐定整體行銷策略的努力則稍有些不足。本研究將從策略行銷中4C分析理論出發，針對雲端運算買者的觀點與看法，提出雲端服務供應企業較為完整的行銷策略分析。研究中也將藉由4C策略行銷的資訊搜集、道德危機、及專屬陷入資產之成本分析，來分析一般企業較為忽略的內顯成本。文中並進一步探討如何使用策略行銷4C的理論，來探究雲端服務供應企業是否進入雲端市場之決策參考的基礎。 本研究將探討全球大廠IBM與HPQ公司從硬體開發轉型至雲端服務的策略與過程，提供雲端運算服務後進業者的參考，藉此希望能協助企業有方向性與策略性的在未來雲端運算市場中佔有商機，擺脫長久低利代工的命運。相信，本研究之成果將可為企業未來發展全球化雲端服務的經營企圖，建立紮實的研究基礎。 / Computing, storage and communication technology keep leading Information and Communication Technology (ICT) development since 1960. Due to the innovation and diffusion of ICT, the ICT products have broadly dissolved in our economic and social life. Recently, ICT industry has already become the most vigorous and largest one in the world. In future, ICT is anticipated to be the most important technology, which keeps affecting the global economy development. Taiwan’s supply chain for the ICT industry overall is quite intact, but the majority corporates are focus on the OEM/ODM roles. For the gradually reduced profit got as playing the OEM/ODM’s roles in the ICT industry supply chain, Taiwan’s enterprises have sensed the warning message for their perspect due to the low profit return. Comparing with other countries, Taiwan’s industry entering the cloud computing industry is late. As one of the new comer for the cloud computing service industry, knowing how to transform the current ICT role (OEM/ODM) to be one of the high-value-added cloud computing service players, the leading enterprise’s strategic planning history will be a good cases study for those late new comers. This research starts from the technology history study of ICT to find out the essence of the cloud computing service, and also by studying the strategic planning of the cloud computing service market leaders to provide the proper strategic planning suggestion for the new comers. Look forwarding this research to help the new comers of the cloud computing industry to catch more global business management idea about this industry, and also can help the current ICT players based on what they owned competence to well plan the strategy for marching towards the higher-value-added clouds computing service industries. Moreover, in the past, for most of the ICT corporates for years are more focusing on the manufactureing compenetence than pre-study the buyers’ needs, and also focusing on the product launch than pays the needed efforts on watching the after-market needed sustaining activities. For the cloud computing service market, due to catch the buyer’s need will be crical and decides whether a supplier can provide the needed services or not. For years, most of the suppliers are more focusing on the cost-down activities than with less strategic planning approach method for the market. This research will base on the strategic marking 4C theory, from the buyer’s view of points, to provide the corporation more complete strategic marking analysis foundation. This research will also from the strategic marketing 4C analysis coverd topics: information collection, normal hazard, asset specificity cost point of view to study most the corporation neglect the hidden exchange costs. It will also go further study by using the strategic marketing analysis 4C theory to practice the decision making criteria as a method for a corporation evaluating whether to enter the cloud computing service market business or not. This research will do the case study of two global corporations, IBM and HPQ. Their strategic planning and the transformation from the hardware developers to be the cloud service suppliers are closer than others for those hardware makers planning entering the cloud computing business to reference. Look forward this research assisting certain enterprises directionally and strategically get the cloud computing business and get rid of the destiny for running the low-profit business as the OEM/ODM roles. Believe the result of research can bring the different view and needed foundation for Taiwan’s enterprises to develop their strategic business plan for entering the cloud computing business.

Virtualisierung und Cloud Computing gehören derzeit zu den wichtigsten Schlagworten für Betreiber von IT Infrastrukturen. Es gibt eine Vielzahl unterschiedlicher Technologien, Produkte und Geschäftsmodelle für vollkommen verschiedene Anwendungsszenarien. Die vorliegende Studie gibt zunächst einen detaillierten Überblick über aktuelle Entwicklungen in Konzepten und Technologien der Virtualisierungstechnologie – von klassischer Servervirtualisierung über Infrastrukturen für virtuelle Arbeitsplätze bis zur Anwendungsvirtualisierung und macht den Versuch einer Klassifikation der Virtualisierungsvarianten. Bei der Betrachtung des Cloud Computing-Konzepts werden deren Grundzüge sowie verschiedene Architekturvarianten und Anwendungsfälle eingeführt. Die ausführliche Untersuchung von Vorteilen des Cloud Computing sowie möglicher Bedenken, die bei der Nutzung von Cloud-Ressourcen im Unternehmen beachtet werden müssen, zeigt, dass Cloud Computing zwar große Chancen bietet, aber nicht für jede Anwendung und nicht für jeden rechtlichen und wirtschaftlichen Rahmen in Frage kommt.. Die anschließende Marktübersicht für Virtualisierungstechnologie zeigt, dass die großen Hersteller – Citrix, Microsoft und VMware – jeweils Produkte für fast alle Virtualisierungsvarianten anbieten und hebt entscheidende Unterschiede bzw. die Stärken der jeweiligen Anbieter heraus. So ist beispielsweise die Lösung von Citrix für Virtual Desktop Infrastructures sehr ausgereift, während Microsoft hier nur auf Standardtechnologie zurückgreifen kann. VMware hat als Marktführer die größte Verbreitung in Rechenzentren gefunden und bietet als einziger Hersteller echte Fehlertoleranz. Microsoft hingegen punktet mit der nahtlosen Integration ihrer Virtualisierungsprodukte in bestehende Windows-Infrastrukturen. Im Bereich der Cloud Computing-Systeme zeigen sich einige quelloffene Softwareprojekte, die durchaus für den produktiven Betrieb von sogenannten privaten Clouds geeignet sind. / Virtualization and Cloud Computing belong to the most important issues for operators of large ICT infrastructures today. There are a large number of various technologies, products, and business models for entirely different application scenarios. The study at hand gives a detailed overview on latest developments in concepts and technologies of virtualization – beginning with classic server virtualization, continuing with infrastructures for virtual workplaces, through to application virtualization and makes an attempt to classify all these variants of virtualization. When investigating on the concepts of Cloud Computing, the report introduces basic principles as well as different types of architecture and use cases. The extensive analysis of benefits of Cloud Computing and possible reservations when using cloud resources within an enterprise context is evidence that Cloud Computing offers great opportunities, but is not worth considering for any kind of application scenario, legal framework or business scenario. The subsequent market study on virtualization technology shows that each of the major manufacturers – Citrix, Microsoft, and VMware – offer products for any variant of virtualization and highlights the important differences between the products and the respective strengths of the vendors. For example, the Citrix solution on Virtual Desktop Infrastructures comes up very well-engineered, while Microsoft can only rely on standard technology in this field. VMware, the market leader in virtualization technology, has gained the biggest popularity in data centers and offers the only product implementing real fault tolerance. On the other hand, Microsoft is able to score with seamless integration of their virtualization products into existing Windows-based infrastructures. In the area of Cloud Computing systems, there are some open source software projects that are very possibly suitable for the productive operation of so called private clouds.

Encryption helps to ensure that information within a session is not compromised. Authentication and access control measures ensure legitimate and appropriate access to information, and prevent inappropriate access to such resources. While encryption, authentication and access control each has its own responsibility in securing a communication session, a combination of these three mechanisms can provide much better protection for information. This thesis addresses encryption, authentication and access control related problems in cloud and distributed environments, since these problems are very common in modern organization environment. The first one is a User-friendly Location-free Encryption System for Mobile Users (UFLE). It is an encryption and authentication system which provides maximum security to sensitive data in distributed environment: corporate, home and outdoors scenarios, but requires minimum user effort (i.e. no biometric entry, or possession of cryptographic tokens) to access the data. It makes users securely and easily access data any time and any place, as well as avoids data breach due to stolen/lost laptops and USB flash. The multi-factor authentication protocol provided in this scheme is also applicable to cloud storage. The second one is a Simple Privacy-Preserving Identity-Management for Cloud Environment (SPICE). It is the first digital identity management system that can satisfy “unlinkability”and “delegatable authentication” in addition to other desirable properties in cloud environment. Unlinkability ensures that none of the cloud service providers (CSPs), even if they collude, can link the transactions of the same user. On the other hand, delegatable authentication is unique to the cloud platform, in which several CSPs may join together to provide a packaged service, with one of them being the source provider which interacts with the clients and performs authentication, while the others are receiving CSPs which will be transparent to the clients. The authentication should be delegatable such that the receiving CSP can authenticate a user without a direct communication with either the user or the registrar, and without fully trusting the source CSP. The third one addresses re-encryption based access control issue in cloud and distributed storage. We propose the first non-transferable proxy re-encryption scheme [16] which successfully achieves the non-transferable property. Proxy re-encryption allows a third-party (the proxy) to re-encrypt a ciphertext which has been encrypted for one party without seeing the underlying plaintext so that it can be decrypted by another. A proxy re-encryption scheme is said to be non-transferable if the proxy and a set of colluding delegatees cannot re-delegate decryption rights to other parties. The scheme can be utilized for a content owner to delegate content decryption rights to users in the untrusted cloud storage. The advantages of using such scheme are: decryption keys are managed by the content owner, and plaintext is always hidden from cloud provider. / published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy