MapReduce is becoming a powerful parallel data processing model and is adopted by many cloud services providers to build cloud computing framework. However, in public cloud systems, several service providers may come from different administration domain out of the user control and may be untrustworthy. Hence, security of MapReduce computation is essential in public cloud systems. Additionally, MapReduce dataprocessing services are long-running, which increases the possibility that an attacker is able to compromise some workers and make them misbehave to corrupt the integrity of all computations allocated to these workers. Thus, the computation integrity is a major concern for Mapreduce user in public cloud environment. In this paper, we propose a new mechanism to ensure the computation integrity of MapReduce in public cloud computing environment. By using replication-based voting method and reputation-based trust management system, our mechanism can efficiently detect both collusive and non-collusive malicious workers and guarantee high computation accuracy with an acceptable overhead.

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Until recently, application developers could often assume a target environment that was homogeneous, reliable, secure, and centrally managed. However, with the advent of collaborative computing and data sharing, more and more new modes of interaction have evolved resulting in the need and use of distributed resources. Work within this community has led to the development of Grid technologies [II, which address precisely these problems. In grid computing, heterogeneous resources distributed geographically are virtualized as a unified whole. Grid computing, as a result, provides enormous opportunities in terms of resource sharing, maximization of resource utilization and virtualization of resources. Because of its immense potential, not only the scientific community, but also the IT enterprise communities are excited about its prospect. A recent survey ranked grid computing as sixth on priority lists for IT spending among indu stry professionals (51 . With thi s much interest, security becomes necessary to provide authentication, authorization, resource protection, secure communication, data confidentiality, data integrity, trust policies management, user key and credential management, service protection, and network security. This paper provides an insight classification of the different mechanisms and methods of security in grid computing environment, and also discusses the solutions for each category and its limitation in order to define the real problems in grid computing security. In our approach, we categorize the security solutions into Resources Level

During the last few years, there has been a rapid and an increasing development and adoption of cloud computing systems, technologies, applications and services. This is owing mainly to many benefits this technology offers for businesses and organizations. However, Cyber-security is considered among the most important issues and concerns for widespread adoption of cloud computing. Among the major issues related with Cloud Computing security we can mention data security, intrusions attacks, confidentiality and data integrity. This paper is dedicated to an overview study of the state of the art of cloud computing cyber-security. With the main objective to identify the main challenges and issues in this field, the different approaches and solutions proposed to address them and the open problems that need to be addressed.

In service oriented computing applications, different resources in grid systems are encapsulated abstractly as services. Sometime, single service software can provide valuable service functions for service consumers, but most of the time, single atomic service can not satisfy them. In this case, the system builds a new composite service, which selects all available qualified grid service for composition. Services with similar and compatible functionality may be offered at different QoS levels. Thus, to build a service process, decisions must be made to select component services at appropriate QoS levels. Therefore, quality of service (QoS) aspects is crucial for selecting the grid services to take part in the composition of the new service. In this paper, we address to the problem of Grid services composition based on QoS parameters with end-to-end constraints, we suggest a new model, which transform any model of composition to a sequential model, and we propose a new approach based on the application of a Fuzzy Multiple Attribute Decision Making technique in order to guide the composition process to selected an optimal composite service.