Research On Searchable Encryption Technology Based On Blockchain

With the popularity of cloud server,users with limited physical storage resources can store a large amount of data to cloud server.However,cloud server is a centralized device,and after storing data into cloud server,data owner loses the control of their data.In order to ensure data security,it needs to be encrypted before uploading.But after encryption,the search for data becomes a problem.Searchable encryption(SE)can solve this problem.At present,most searchable encryption schemes are combined with cloud server.But searchable encryption based on cloud server has many drawbacks.Blockchain is a decentralized shared ledger that can solve these problems of the centralized cloud server.However,at present,the searchable encryption scheme based on blockchain has problems of low search efficiency,large amount of computation and distrust among participants.Therefore,it is necessary to design a searchable encryption scheme with the advantages of high search efficiency,lightweight and supporting fair payment.In order to solve these problems,this paper combines blockchain with searchable encryption,and proposes new searchable encryption schemes by using cryptography and other related technologies.The specific research contents are as follows:(1)In order to solve the problem of low search efficiency on blockchain,a keyword complete binary tree searchable encryption scheme using blockchain(KCB-BC-SE)is proposed.The keyword complete binary tree is introduced into searchable encryption scheme on blockchain.Using keyword complete binary tree to construct index structure can effectively improve the data search efficiency.Data can be searched by triggering smart contract on blockchain and data sharing can be realized.According to the size of data,KCB-BC-SE can be divided into KCB-BC-SE scheme for lightweight data(KCBC-SE-LD)and KCB-BC-SE scheme for big data(KCBC-SE-BD).Meanwhile,the scheme is indistinguishable secure under the chosen keyword attack.Through theoretical analysis and experimental results,this scheme improves the search efficiency of searchable encryption scheme using blockchain.(2)Aiming at the problem of fair payment and data security in searchable encryption,a blockchain-based multi-user verifiable oblivious keyword search(BC-MVOKS)is proposed.A conjunctive keyword search BC-MVOKS scheme is proposed to improve traditional OKS.At present,oblivious keyword search only supports user authentication of single keyword,so this scheme realizes user authentication of multi-keyword.In addition,BC-MVOKS achieves fair payment using blockchain to solve the trust problem among participants.Aiming at large amount of computation issue among participants,a lightweight multi-keyword search BC-MVOKS(LM-BC-MVOKS)scheme is proposed.This scheme uses polynomial to construct index structure,and realizes multi-keyword search based on cryptography knowledge and polynomial index structure.The analysis shows that the computation of LM-BC-MVOKS is less than that of other searchable encryption schemes.LM-BC-MVOKS scheme further reduces the computational burden of data owner and data user.Finally,the experimental results show that this scheme shortens time of first user authorization and improves the oblivious keyword search scheme by blockchain.