Research And Implement Of Attribute-based Encryption Scheme With Policy Hidden In Cloud Environment

In recent years,with the development of cloud computing technology,the problem of access control in the Personal Health Records(PHR)system under cloud computing is becoming a hot research topic gradually.Currently,the ciphertext-policy attribute based encryption(CP-ABE)scheme is considered to be the most suitable scheme for access control in cloud environment.However,the traditional CP-ABE scheme does not hide the access policy and sometimes the access policy itself contains much sensitive information,will leak some privacy information.Therefore,this paper will focus on the problem about access policy hidden.Details are as follows:(1)A CP-ABE scheme with access policy hidden based LSSS is proposed.It could express any policy by employing Linear Secret Sharing Schemes(LSSS).We adopt composite order bilinear groups whose order is the product of three distinct primes to construct the scheme and it could be proved chosen-plaintext attack(CPA)secure by using dual system encryption technology.Compared with the other scheme based LSSS which is partially hidden policy,on the premise of realizing hidden policy,our scheme not only reduces the order of bilinear group,but also improves the encryption efficiency.(2)A CP-ABE scheme with access policy hidden partly based access tree is proposed.The scheme adopts access tree to express policy which is simple and intuitive.It uses the method of inperfect access tree without leaf nodes which is sent to users to implement the policy hidden,and based on DBDH assumption,our scheme is proved fully secure under standard model.Compared with other schemes that also hide policy,this scheme reduces the length of the private key and the ciphertext,improves the decryption efficiency,and is more suitable for the users with limited computing power.(3)We apply the CP-ABE scheme with policy hidden to the PHR system in cloud environment,and prove the feasibility of the policy hidden CP-ABE scheme through simulation experiments.