Decentralized Access Control of Data in Cloud Services using Key Policy Attribute Based Encryption

Cloud storage is a storage of data online in cloud which is accessible from multiple and connected resources. Cloud storage can provide good accessibility and reliability, strong protection, disaster recovery, and lowest cost. Cloud storage having important functionality i.e. securely, efficiently, flexibly sharing data with others. New public–key encryption which is called as Key-aggregate cryptosystem (KAC) is introduced. Key-aggregate cryptosystem produce constant size cipher texts such that efficient delegation of decryption rights for any set of cipher text are possible. Any set of secret keys can be aggregated and make them as single key, which encompasses power of all the keys being aggregated. This aggregate key can be sent to the others for decryption of cipher text set and remaining encrypted files outside the set are remains confidential. The security mechanisms for private and public clouds are different. It may be possible that an unauthorized user can access the data from the public clouds. Hence, it is of critical importance that the client should be able to verify the integrity of the data stored in the un-trusted server. In order to address the security issues, Trusted Third Party Auditing (TPA) is used as a service for private and public clouds, which offers various services to check for the integrity of the data.