© 2013, IJARCSSE All Rights Reserved Page | 1032 Volume 3, Issue 11, November 2013 ISSN: 2277 128X International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com Third Party Auditing (TPA) for Data Storage Security in Cloud with RC5 Algorithm Miss. Nupoor M. Yawale Prof. V. B. Gadichha M.E. Second year CSE P R Patil COET P R Patil COET, Amravati. INDIA. Amravati. INDIA. Abstract-- Cloud computing is an internet based computing which enables sharing of services. Cloud computing allows users to use applications without installation any application and access their personal files and application at any computer with internet or intranet access. Many users place their data in the cloud, so correctness of data and security is a prime concern.Cloud Computing is technology for next generation Information and Software enabled work that is capable of changing the software working environment. It is interconnecting the large-scalecomputing resources to effectively integrate, and to computing resources as a service to users. To ensure the correctness of data, we consider the task of allowing a third party auditor (TPA), on behalf of the cloud client, to verify the integrity of the data stored in the cloud., the auditing process should bring in no new vulnerabilities towards user data privacy, and introduce no additional online burden to user. In this paper, we propose a secure cloud storage system supporting privacy-preserving public auditing. We further extend our result to enable the TPA to perform audits for multiple users simultaneously and efficiently with RC5 Encryption Algorithm. This shows the proposed scheme is highly efficient and data modification attack, and even server colluding attacks. Here Work is focuses on RC5 Encryption Algorithm for stored data in cloud. Resulted encrypted method is secure and easy to use. Keywords-- Cloud computing, Encryption, Data integrity, Third Party Auditor (TPA), RC5 Algorithm, privacy- preserving, public auditability. I. INTRODUCTION A. Cloud Computing: Cloud computing is innovation that uses advanced computational power and improved storage capabilities. Cloud computing is a long dreamed vision of computing utility, which enable the sharing of services over the internet. Cloud is a large group of interconnected computers, which is a major change in how we store information and run application. Cloud computing is a shared pool of configurable computing resources, on-demand network access and provisioned by the service provider [1]. The advantage of cloud is cost savings. The prime disadvantage is security. Cloud computing is used by many software industries. Since the security is not provided in cloud, many companies adopt their unique security structure. The data placed in the cloud is accessible to everyone, security is not guaranteed. To ensure security, cryptographic techniques cannot be directly adopted. Sometimes the cloud service provider may hide the data corruptions to maintain the reputation. To avoid this problem, we introduce an effective third party auditor to audit the user‟s outsourced data when needed. The security is achieved by RC5 Encryption Algorithm. We utilized public key based homomorphic authenticator with random masking to achieve privacy preserving auditing protocol.TPA performs the auditing task for each user.[2] B. Third party Auditor (TPA): Third Party Auditor is kind of inspector. There are two categories: private auditability and public auditability. Although private auditability can achieve higher scheme efficiency, public auditability allows anyone, not just the client (data owner), to challenge the cloud server for the correctness of data storage while keeping no private information. To let off the burden of management of data of the data owner, TPA will audit the data of client. It eliminates the involvement of the client by auditing that whether his data stored in the cloud are indeed intact, which can be important in achieving economies of scale for Cloud Computing. The released audit report would help owners to evaluate the risk of their subscribed cloud data services, and it will also be beneficial to the cloud service provider to improve their cloud based service platform [3]. Hence TPA will help data owner to make sure that his data are safe in the cloud and management of data will be easy and less burdening to data owner. Cloud consumers save data in cloud server so that security as well as data storage correctness is primary concern. A novel and homogeneous structure is introduced [4] to provide security to different cloud types. To achieve data storage security, RC5 algorithm is used. RC5 algorithm is efficient and safer than the former algorithms. It allows TPA to perform multiple auditing tasks for different users at the same. II. OBJECTIVE Our contribution in this paper is summarized as follows: 1) We motivate the public auditing system of data storage security in Cloud Computing and provide a privacy-preserving auditing protocol, i.e., our scheme supports an external auditor to audit user‟s outsourced data in the cloud without learning knowledge on the data content.