Research On Searchable Attribute-based Encryption Schemes With Hidden Access Policy In Cloud Storage Environment

Since the 21 st century,electronic technology and information technology have been booming,The computing power and load capacity of information system have been greatly improved.The concept of cloud computing has been put forward by the academic community,which uses distributed architecture to establish information cluster and centralizes the idle computing and storage resources of "cloud" servers to be flexibly scheduled by users.The security of cloud users' private data needs a feasible data access control scheme to guarantee.The cloud environment has a huge amount of users and data.The traditional scheme in the field of cryptography is not practical in actual cloud environment.Therefore,an attribute based encryption method has been formally proposed,which can be used to implement fine-grained access control mechanism in cloud storage environment.Nowadays,attribute-based encryption has become the cornerstone of cloud data access control,and a large number of algorithms and schemes have been proposed.Firstly,this thesis studies the current situation of data access control in the cloud storage environment,and obtains several functional requirements that need to be solved urgently in practical application: providing fine-grained access control for private data,searching key words of data ciphertext without exposing index information,protecting the confidentiality of access control strategy,and revoking and updating user attributes.In the next part of this thesis,the existing schemes in the above subdivisions are studied deeply.The typical construction methods and shortcomings of each field are summarized.On this basis,two schemes are proposed.(1)Efficient Searchable Attribute-Based Encryption Scheme with Hidden Policy,ES-ABE-HP is proposed.The ES-ABE-HP scheme controls the length of the user's private key to a fixed length,effectively shortens the length of the ciphertext.The decryption procedure is simpler than the existing scheme,so it has a high encryption and decryption efficiency.It hides the access policy in the ciphertext,ensuring the confidentiality of the access control policy.In addition,it realizes the ciphertext association based on the attribute encryption Combined keyword search function.Through program implementation,it can be verified that ES-ABE-HP has obvious performance advantages compared with the existing searchable attribute-based encryption scheme.(2)Searchable and Revocable Attribute-Based Encryption Scheme with Hidden Policy,SR-ABE-HP is proposed.SR-ABE-HP scheme not only has the function of keyword search,but also can revoke the user attribute.At the same time,it also hides the access policy in the ciphertext,which effectively guarantees the security of the access control policy.Compared with ES-ABE-HP scheme,SR-ABE-HP scheme expands the function of user attribute revocation,and provides a reliable searchable access control method for application scenarios that need to update user attributes regularly.SR-ABEHP can resist indistinguishable choice plaintext attack and indistinguishable choice keyword attack.