SLA-Based Trust Model for Cloud Computing

Cloud computing is a new form of technology, which infrastructure, developing platform, software, and storage can be delivered as a service in a pay as you use cost model. However, for critical business application and more sensitive information, cloud providers must be selected based on high level of trustworthiness. In this paper, we present a trust model to evaluate cloud services in order to help cloud users select the most reliable resources. We integrate our previous work “conceptual SLA framework for cloud computing” with the proposed trust management model to present a new solution of defining the reliable criteria for the selection process of cloud providers

Scalable and Socially Inspired Blockchain Architecture for the Organic Food Supply Chain

Organic food supply chains are faced with heavy pressure to increase their output to meet the global demand. This confronts various challenges including scandals, adulteration, contamination, and growing regulations. As an alternative to third-party certification, Participatory Guarantee Systems (PGS) are popular community-based quality assurance system that integrates the social verification context into the organic certification process. As PGS is a local community-driven system, it has inherent limitations in the scalability of reaching consensus as the size of participants increases. The organic food industry has the potential to grow globally therefore, an appropriate scalable consensus mechanism is needed to deal with community-level consensus as an alternative to the existing PGS system. Blockchain architecture with hybrid consensus mechanisms seems to be the potential solution to address the trust and scalability issues in the organic food supply chain. This paper proposes a socially inspired hybrid blockchain architecture for the organic food supply chain to address the scalability issues via hybridizing two consensuses’ mechanisms with the combined advantages of Proof of Authority (PoA) and Federated Byzantine Agreement (FBA). In the proposed architecture, much eminent aspect of community-level trust is integrated into the consensus process. Furthermore, this paper presents a concept-level validation as a qualitative analysis of the proposed architecture based on experts’ opinions. Concept-level validation of the proposed model acknowledged that, in the context of social verification, the credibility of the organic products would be enhanced, and hybridization of the consensuses would mitigate the scalability issues

SLA-based trust model for secure cloud computing

Cloud computing has changed the strategy used for providing distributed services to many business and government agents. Cloud computing delivers scalable and on-demand services to most users in different domains. However, this new technology has also created many challenges for service providers and customers, especially for those users who already own complicated legacy systems. This thesis discusses the challenges of, and proposes solutions to, the issues of dynamic pricing, management of service level agreements (SLA), performance measurement methods and trust management for cloud computing.In cloud computing, a dynamic pricing scheme is very important to allow cloud providers to estimate the price of cloud services. Moreover, the dynamic pricing scheme can be used by cloud providers to optimize the total cost of cloud data centres and correlate the price of the service with the revenue model of service. In the context of cloud computing, dynamic pricing methods from the perspective of cloud providers and cloud customers are missing from the existing literature. A dynamic pricing scheme for cloud computing must take into account all the requirements of building and operating cloud data centres. Furthermore, a cloud pricing scheme must consider issues of service level agreements with cloud customers.I propose a dynamic pricing methodology which provides adequate estimating methods for decision makers who want to calculate the benefits and assess the risks of using cloud technology. I analyse the results and evaluate the solutions produced by the proposed scheme. I conclude that my proposed scheme of dynamic pricing can be used to increase the total revenue of cloud service providers and help cloud customers to select cloud service providers with a good quality level of service.Regarding the concept of SLA, I provide an SLA definition in the context of cloud computing to achieve the aim of presenting a clearly structured SLA for cloud users and improving the means of establishing a trustworthy relationship between service provider and customer. In order to provide a reliable methodology for measuring the performance of cloud platforms, I develop performance metrics to measure and compare the scalability of the virtualization resources of cloud data centres. First, I discuss the need for a reliable method of comparing the performance of various cloud services currently being offered. Then, I develop a different type of metrics and propose a suitable methodology to measure the scalability using these metrics. I focus on virtualization resources such as CPU, storage disk, and network infrastructure.To solve the problem of evaluating the trustworthiness of cloud services, this thesis develops a model for each of the dimensions for Infrastructure as a Service (IaaS) using fuzzy-set theory. I use the Takagi-Sugeno fuzzy-inference approach to develop an overall measure of trust value for the cloud providers. It is not easy to evaluate the cloud metrics for all types of cloud services. So, in this thesis, I use Infrastructure as a Service (IaaS) as a main example when I collect the data and apply the fuzzy model to evaluate trust in terms of cloud computing. Tests and results are presented to evaluate the effectiveness and robustness of the proposed model

Modèle de confiance et ontologie probabiliste pilotés par réseaux bayésiens pour la gestion des accords de services dans l’environnement de services infonuagiques

L’infonuage est un nouveau paradigme de services informatiques disponibles à la demande qui a connu une croissance fulgurante au cours de ces dix dernières années. Le fournisseur du modèle de déploiement public des services infonuagiques décrit le service à fournir, le prix, les pénalités en cas de violation des spécifications à travers un document. Ce document s’appelle le contrat de niveau de service (SLA). La signature de ce contrat par le client et le fournisseur scelle la garantie de la qualité de service à recevoir. Ceci impose au fournisseur de gérer efficacement ses ressources afin de respecter ses engagements. Malheureusement, la violation des spécifications du SLA se révèle courante, généralement en raison de l’incertitude sur le comportement du client qui peut produire un nombre variable de requêtes vu que les ressources lui semblent illimitées. Ce comportement peut, dans un premier temps, avoir un impact direct sur la disponibilité du service. Dans un second temps, des violations à répétition risquent d'influer sur le niveau de confiance du fournisseur et sur sa réputation à respecter ses engagements. Pour faire face à ces problèmes, nous avons proposé un cadre d’applications piloté par réseau bayésien qui permet, premièrement, de classifier les fournisseurs dans un répertoire en fonction de leur niveau de confiance. Celui-ci peut être géré par une entité tierce. Un client va choisir un fournisseur dans ce répertoire avant de commencer à négocier le SLA. Deuxièmement, nous avons développé une ontologie probabiliste basée sur un réseau bayésien à entités multiples pouvant tenir compte de l’incertitude et anticiper les violations par inférence. Cette ontologie permet de faire des prédictions afin de prévenir des violations en se basant sur les données historiques comme base de connaissances. Les résultats obtenus montrent l’efficacité de l’ontologie probabiliste pour la prédiction de violation dans l’ensemble des paramètres SLA appliqués dans un environnement infonuagique.Cloud Computing is a new paradigm of IT on-demand services which has experienced tremendous growth over the past decade. The provider of Cloud computing services describes the service to be provided, its cost, and penalties for service violations within a document. This document is called Service Level Agreement (SLA). The signature of this contract by the customer and the provider guarantees the quality of service received by the customer. It also entails the provider to manage its resources efficiently to meet its commitments. Unfortunately, the SLA violation is common; it is usually caused by uncertainty about customer behavior that can make variable number of requests assuming that resources are boundless. This behavior may have an impact on the availability of the service, thus its related SLA. Repeated SLA violations will definitively have an impact on the trust level that the customer has about the provider that might no longer enjoys a good reputation in meeting its commitments. To cope with these problems, we have proposed a Framework driven by a Bayesian network that allows, first, to classify the suppliers in a Cloud directory according to their trust level. This directory can be managed by a third party entity, in which a client will choose a provider before starting SLA negotiation. Secondly, we have developed a probabilistic ontology, based on a Multi-Entity Bayesian network, which takes into account uncertainty, in the customer behavior, and makes predictions by inference; these predictions help preventing SLA violations based on historical data.. The results show the effectiveness of the probabilistic ontology for the prediction of SLA violations in a Cloud Computing environment

Performance Evaluation of three Data Access Control Schemes for Cloud Computing

Cloud services are flourishing recently, both among computer users and business enterprises. They deliver remote, on-demand, convenient services for data storage, access and processing. While embracing the benefits brought by various cloud services, the consumers are faced with data disclosure, privacy leaks and malicious attacks. Therefore, it is important to use strong access control policies to maintain the security and confidentiality of the data stored in the cloud. This thesis studies the performance of three existing security schemes proposed for cloud data access control on the basis of trust and reputation. We implement the three schemes and conduct computation complexity analysis, security analysis and performance evaluation. This thesis introduces the implementation of a number of cryptographic algorithms applied in the above data access control schemes, including Proxy Re-encryption (PRE) and Ciphertext-Policy Attribute Based Encryption (CP-ABE), reputation generation and secure data transmission over Secure Socket Layer (SSL). We summarize the evaluation results and compare the performances in the aspects of computation and communication costs, flexibility, scalability and feasibility of practical usage. Pros and cons, as well as suitable application scenarios of the three schemes are further discussed