Attribute-based Searchable Encryption Schemes On Ideal Lattices

Cloud computing technology makes data storage more efficient and convenient.More and more users store their data in the cloud after encryption.Ciphertext policy attribute-based encryption(CP-ABE)is a kind of encryption technology that can guarantee fine-grained access control.It avoids multiple encryption for different users and has wide application prospects in the open network environment.But data encryption makes data search a very challenging task in cloud computing.Public-key encryption with keyword search encryption(PEKS)provides an effective way to search encrypted data stored in the cloud.The combination of the CP-ABE and PEKS scheme can simultaneously achieve fine-grained access control to the search authority of data users and search for ciphertext by the keywords.However,the existing researches are all based on bilinear pairs.With the development of quantum computers,these schemes will be unsafe.Lattices cryptography has the advantage of resisting the quantum attack,the scheme of attribute-based encryption on lattices has become a research hotspot in recent years,but few people study searchable encryption schemes on lattices.Besides,the assumption of learning with error on the ring(R-LWE)on the ideal lattices has the characteristics of the simple algebraic structure and simple calculation,which can make the scheme more efficient and flexible.Therefore,this thesis studies the attribute-based searchable encryption(CP-ABSE)scheme on the ideal lattices.The main work of this thesis is as follow:(1)This thesis proposes a CP-ABSE scheme based on R-LWE.It can realize the keyword search and fine-grained data access control for encrypted data at the same time.In this scheme,the data owner can encrypt the keywords and plaintext with the specified attribute set,the data user generates the search token related to his attribute,outsource the tedious search operation to the cloud.Only the users who satisfy the access structure can search with a keyword in the cloud environment,and then decrypt the cipher text related to the keyword.(2)Then,a multi-authority(MA)CP-ABSE scheme is proposed.If only one trusted authority generates the key of all users,it may lead to single point failure,overload,and some security risks.Therefore,this thesis looks for a method to extend the CP-ABSE scheme of the single authority to the multi-authority environment.Each authority can manage some attributes,data owner and data user can interact with these authorities.And a specific MA-CP-ABSE scheme on the ideal lattice is given,which is more practical and safer than the single authority scheme.(3)It is proved that the two schemes proposed in this thesis are safe against the selection of chosen-plaintext attack and are indistinguishable under the selected keyword attack in the random oracle model under R-LWE.Compared with other schemes on bilinear pairs,the scheme in this thesis is more straightforward,efficient and safer.