Cloud Computing is the Shared pool of resources, which can be requested on-demand to enjoy the services and application. The data owner remotely store their data services and application which can be retrieved when required. The clients save their data on the storage services and gets free from the burden of maintaining the data. But some of the incidences in the history of cloud computing shows that they are not reliable at times Ex: Gmail disaster, Amazon S3 downfall. Some of the major challenging issues of the cloud computing are availability of service, data lock in, Data confidentiality and Auditability, Data transfer Bottleneck etc. The data outsourcing makes the owner free from data storage, physical organization and security, which is the need of both enterprises and individuals with high service level requirements. In order to smooth the progress of rapid deployment of cloud data storage service and regain security assurances with outsourced data dependability, efficient methods that enable on-demand data correctness verification on behalf of cloud data owners have to be designed. While public audit ability, we can have a trusted third audit party who have knowledge and capability to evaluate the danger of outsourced data whenever demanded. This is a cost effective method for data owners to believe on the cloud. We have challenges that need to be resolved for publicly auditable secure cloud storage services to become a reality.

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