Data deduplication is one of compression method of data for eliminating duplicate copies of repeating data that is mainly used to reduced the amount of storage space and bandwidth. Cloud computing systems have been made possible through the use of large –scale clusters,service –oriented architecture (SOA),web services ad virtualization.While the idea offering resources via web services is common place in cloud computing ,little attention has been paid to clients themselves specifically ,human operators.Despite that clouds host a variety of resources which in turn are accessible to variety of clients ,support for human users is minimal .To provide better security ,this paper makes the first attempt to formally address the problem of authentication ,integrity and availability.By using Tag generation , moreover one of additional cloud storage service such that Cluster as a Service (CaaS) can make secure deduplication possible and reduced cloud storage space.With out key generation ,attribute based encryption makes secure data deduplication in the cluster of computers.