Research On Public Key Encryption With Keyword Search Technologies For Cloud Storage Security

With the development of information era,the amount of data becomes increasingly large.The emergence of cloud storage technology brings great convenience to data storage and sharing,but brings great security threats at the same time.The cloud storage server(CSS)is often vulnerable to attacks from external and internal adversaries.Although common encryption technologies can protect data privacy,it needs to download all remote files for local decryption one by one,which undoubtedly increases the waste of system resources.Although data encryption is considered to be a simple and effective solution to protect data confidentiality,it will make the retrieval over encrypted data extremely difficult.Therefore,searchable encryption(SE),which allows users to conduct secure retrieval,has attracted great attention from both industry and academia.However,most SE schemes can only support single keyword search,and face the problems of certificate management and key escrow.In fact,CSS is not completely trusted.Semi-trusted CSS may perform partial search to save its own resources.In addition,many existing schemes cannot support file update operations,and thus the flexibility of schemes are limited.Therefore,it is very important to design SE schemes which are suitable for the actual scenarios.The research results of this thesis are as follows:Aiming at the problems of certificate management and key escrow in traditional SE schemes,a server-aided certificateless public key encryption with multiple keyword search scheme is proposed.Using the idea of certificateless public key encryption,the proposed scheme encrypts keywords and eliminates the problems of certificate management and key escrow.At the same time,the scheme supports conjunctive keyword search,which allows data users to submit multiple keyword in one query.It avoids the problem of inaccurate results in the process of single keyword search and makes it more suitable for the actual needs.Furthermore,the user interacts with the assistant server to generate pre-processed keywords to resist keyword guessing attack(KGA)in the system initialization phase.Security proof and simulation analysis show that the scheme is secure and efficient.Aiming at the problem that existing SE schemes cannot support ciphertext result verification and file update,a blockchain-enabled public key encryption with multi-keyword search scheme is proposed.In order to support the verifiability of ciphertext results,the integrity of data is protected by numbering the files and combining them with ciphertext.At the same time,the specific operation process of file update is given,which makes the scheme flexible and avoids the re-initialization of the algorithms in the scheme.In particular,the scheme takes into account the encryption and decryption of the file,in which the symmetric key is generated based on the negotiation between the data user and the data owner.Thus,the communication overhead is reduced compared with the key negotiation in the traditional symmetric cryptosystem.In addition,the scheme ensures the fairness of transaction data between the data owner and the data user through the smart contract technology in the Ethereum blockchain.The formal security analysis based on the random oracle model shows that the scheme can resist internal KGA,and the comparative analysis with respect to the function,storage overhead and computing overhead shows that the scheme is efficient.