Cloud computing is an important model for delivering valuable business services to the cloud users. Cloud service consider as online storage where the data is remotely stored, managed and backed up based on pay per use. The user store their files in online and access them from anywhere via the internet. Data storage security is a primary concern when entrusting an organization to keep track their sensitive information in cloud but not under the direct control of that organization. The main challenge of cloud is to ensure the correctness of user’s data in the cloud storage. It focuses on cloud data storage security, always which has been an important aspect of quality of service.