Secured Data Sharing and Access Control for Cloud Computing Systems using CP-ABE Algorithm with Verifiable Delegation

In the cloud, for achieving access control and data security, data owners adopt attribute-based encryption to encrypt the stored data. Users with limited computing power are however more likely to delegate the mask of the decryption task to the cloud servers to reduce the computing cost. As a result, attribute-based encryption with delegation emerges. Still, there are some problems like misrepresenting or replacing the delegated cipher text, access policy may not be flexible enough during encryption and cloud servers may cheat the eligible users by responding them that they are ineligible for the purpose of cost saving. Since policy for general circuits enables to achieve the strongest form of access control, a construction for realizing circuit cipher text-policy attribute-based hybrid encryption with verifiable delegation has been developed. This system is combined with verifiable delegation and encrypt-then-Mac mechanism, the data confidentiality, the fine-grained access control and the correctness of the delegated results are well guaranteed at the same time.