Cloud Storage permits users to remotely store their data and also provides users with on-demand self service from a shared pool of configurable and computable resources and that can be rapidly provisioned and realized with minimal management efforts or service provider interaction. Despite of its advantage, outsourcing storage prompts a number of interesting challenges. One of the important factors that need to be taken into consideration is to assure the user about the correctness of his outsourced data. Also, cloud user should be able to use the cloud storage without worrying for the need to verify its correctness. Thus, enabling public verifiability for cloud storage system is of critical importance so that cloud user can resort to an external audit party i.e. third party auditor (TPA) to check the correctness of outsourced data. For TPA to be secure and effective, the auditing process should not introduce no new vulnerabilities that violate users’ data privacy and no additional online burden to cloud user. In this paper, a secure storage system that supports user privacy preserving and auditing is implemented using RC4 algorithm to increase efficiency. To speed up auditing by TPA, batch auditing scheme is introduced. Proposed scheme helps to achieve secure and efficient dynamic operations on blocks of data as well as recovery of corrupted data or lost data can be achieved by replicating data on backup servers
