Abstract: In Cloud computing involves deploying groups of remote servers and software networks that allow centralized data storage and online access to computer services or resources. Clouds can be classified as public, private or hybrid. Cloud service providers offer both highly available storage and massively parallel computing resources at relatively low costs. As cloud computing becomes prevalent, an increasing amount of data is being stored in the cloud and shared by users with specified privileges, which define the access rights of the stored data. One critical challenge of cloud storage services is the management of the ever-increasing volume of data.Datadeduplication is a specialized data compression technique for eliminating duplicate copies of repeating data. This technique is used to improve storage utilization and can also be applied to network data transfers to reduce the number of bytes that must be sent and save bandwidth. To protect the confidentiality of sensitive data while supporting deduplication, the convergent encryption technique is used to encrypt the data before outsourcing. It encrypts/decrypts a data copy with a convergent key, which is obtained by computing the cryptographic hash value of the content of the data copy. Convergent encryption allows the cloud to perform deduplication on the ciphertexts and the proof of ownership prevents the unauthorized user to access the file. To enhance the system in security OAuth is used. OAuth (Open Authorization) is an open protocol for token-based authentication and authorization on the Internet used in hybrid cloud to enhance the security. OAuth enables the system to ensure that the user is an authenticated person or not. Only such authenticated user got the token for uploading and downloading in pubic cloud.

Keywords: OAuth, S-SCP, convergent encryption