Blockchain-based Searchable Encryption Technology And Applications

With the rapid development of network technology,cloud computing and cloud storage have become the basic services of the Internet.Individual users and enterprise users are willing to host their data to cloud server storage.However,the data outsourced to cloud server computing or storage is faced with the risk of data corruption and data leakage.Before users outsource sensitive data to cloud server,they usually choose to encrypt data.This measure effectively protects data privacy,but it hinders the use of data.The emergence of searchable encryption technology provides an effective way to solve this problem.Users can directly perform complex operations such as search and calculation on encrypted data.Especially after blockchain technology appeared,researchers proposed some searchable encryption systems and schemes based on blockchain.These schemes try to utilize the advantages of intelligent contract to realize fair transaction among data owners,data users and cloud storage entities.The potential malicious behavior of the server is constrained by the transparency and the public auditability of blockchain.However,the existing scheme generally adopts corresponding countermeasures against malicious acts,and there is no punishment.In addition,such schemes are still lack of the characteristics of the specific structure,lack of generality,or focus on a certain function.In view of the shortcomings and defects of blockchain based searchable encryption technology,the following research work is carried out in this thesis.(1)The searchable encryption supporting data update and fair payment is proposed.The existing scheme is analyzed.Combining blockchain technology with searchable encryption technology,a searchable encryption scheme based on tree index structure is proposed.For malicious servers,the traceability and tamperability of blockchain are used to prevent malicious servers from returning wrong results,and intelligent contracts are designed to ensure the fairness of transactions.Compared with other index structures,tree index structure can improve the retrieval efficiency and realize the time complexity of sub linear search,and also can update the document data effectively.The security analysis of the scheme is carried out in this paper.The results show that the scheme meets the ind CKA security.Compared with the same scheme,the scheme has a certain comprehensive advantage in efficiency.(2)A searchable encryption scheme is proposed for the results of electronic health record sharing.Based on the analysis of the existing schemes,the verifiable searchable encryption scheme is proposed by combining the basic tools such as blockchain technology and intelligent contract.The scheme can realize the effective update of data while multi keyword search is realized.The scheme uses RSA accumulator to design intelligent contract to verify the integrity of documents.After the verification,the two parties involved in the transaction can realize fair transaction.The user gets the correct search results,and the server gets the corresponding cost.The scheme can effectively ensure the safe storage and efficient sharing of data when sharing electronic health records.The security analysis shows that the scheme of this paper realizes the non adaptive semantic security.The performance analysis shows that the scheme is effective and feasible.