Ciphertext retrieval via attribute-based FHE in cloud computing

In order to ensure the security of users' information effectively, this paper investigates ciphertext-based attribute encryption. Homomorphic encryption can settle the problems of data privacy in cloud environments, in the way that can be operated directly to achieve the same result as for plaintext operations. In this paper, on the premise of attribute encryption, we propose an attribute-based fully homomorphism encryption scheme with LSSS matrix and a ciphertext-based retrieval scheme on this basis. Firstly, the retrieval scheme supports fine-grained cum flexible access control along with "Query-Response" mechanism to enable users to efficiently retrieve desired data from cloud servers. Secondly, the scheme supports considerable flexibility to revoke system privileges from users without updating the key client, which reduces the burden of the client greatly. Security analysis shows that the scheme can resist collusion attack. A comparison of the performance with existing CP-ABE schemes indicates that our scheme reduces the computation cost greatly for users and guarantees only the owners of the evaluation keys can perform ciphertext retrieval, which is also one of the main advantages of the proposed scheme.