Researches On Attribute-Based Searchable Encryption Schemes On Lattice

The explosive growth of information has spawned an outsourced storage model.Although this model provides convenience for users to store data,there are still disadvantages that cannot be ignored.That is,because data is stored off-site,users do not have absolute control over their own data Rights and untrust service providers maybe leak and abuse data and user privacy.In this regard,a feasible solution is to encrypt the data before uploading it,which can effectively protect data security and user privacy.Attribute-based encryption is widely used for data encryption because of its flexible and changeable access control structure,which can be applied to one-to-many application scenarios.At present,the bilinear pairing technology is basically used in the attribute-based encryption system.The main disadvantage of this kind of schemes is that the schemes often need to calculate the bilinear pair multiple times during the encryption and decryption process,so the calculation efficiency is low.With the rapid development of quantum computers,most of the existing attribute-based encryption schemes based on bilinear pairing technology cannot resist quantum attacks,and there are certain security threats.In recent years,in view of the advantages of cryptographic schemes based on lattice theory,which are resistant to quantum attacks,strong security proof in the worst case,and highly efficient,the research on designing cryptosystems based on lattice has received great attention.In addition,encrypted data causes the data to lose its original semantic characteristics,which will cause two major problems:First,the data file loses its retrieved characteristics,which causes the problem that data cannot be flexibly shared.Second,the service provider cannot process data efficiently.This thesis uses the attribute-based encryption scheme from lattice to study the above two issues and achieves the following results:1.An attribute-based searchable encryption scheme from lattice on Ethereum is proposed,which solves the problem that encrypted data cannot be flexibly shared.The solution uses Ethereum and IPFS systems to solve the problem of single point failure in traditional cloud storage.And data owner in the solution replaces the private key generator to generate private key for user,avoiding the key abuse and privacy leakage caused by the key escrow problem in the traditional solutions.The use of Ethereum's smart contract solves the reliability of keyword search results in the case of untrusted service providers in cloud storage.Compared with the traditional schemes,the scheme can not only achieve fine-grained retrieval of encrypted keywords,but also be more secure andresistant to quantum attacks.Under the assumption of LWE,the security of the scheme is proved.Finally,the performance of the scheme is analyzed and compared,and the simulation results are given.2.An attribute-based homomorphic searchable encryption scheme from lattice is proposed.This scheme is constructed based on key-policy attribute-based encryption scheme on LWE.The scheme uses the property of homomorphic encryption,and performs homomorphic operations on the encrypted keyword and public key according to the circuit determined by the access policy,which shortens the length of the initial encrypted keyword.Since homomorphic evaluation is a public operation,an agent or service provider is deployed in the system to perform homomorphic operations on encrypted keyword to generate encrypted keyword under the access policy,which avoids multiple users repeating the same operation and reducing computing costs for limited users and devices.In the scheme,the key is a single matrix that only corresponds to the final output of the circuit.The scheme uses arithmetic circuits to represent Boolean expressions corresponding to access structures formed by AND gates,OR gates,and introduces negative attributes,which improves the flexibility of the access structure of the scheme.Finally,the thesis proves the security of the scheme,analyzes and compares the performance,and gives simulation results.