Secure Attribute Based Encryption with Valid Outsourced Decryption

Cloud computing is the on-demand delivery of compute power, database storage, applications, and other IT resources through a cloud services platform via the internet with pay-as-you-go pricing. Cloud users data security is very essential need of the cloud computing. The technique of cryptography provides the way for data security in cloud. Attribute based encryption is a special kind of encryption that supports complex access control over encrypted data. But the decryption using personal devices increase complexity. Outsourcing the encrypted data to a third party will overcome this problem. Even though the outsourcing reduces complexity, it is not possible to trust the third party. So security of the data used for outsourcing is important. This paper uses the concept of partial outsourced decryption. It allows the proxy (third party) only to perform the partial decryption. The receiver can do the remaining decryption by simple operations. Thus the proxy does not learn anything about the encrypted message. It is very essential that the correctness of outsourced decryption must be verified. RCCA-secure and CPA-secure are two systems used for verifying the correctness of the outsourced decryption. Even though the system is secure there may be chances of attack that unauthorized user attempts to access files. This paper introduces a blocking mechanism that blocks the one who perform unauthorized access.