Dynamic Symmetric Searchable Encryption Mechanism With Low Memory Index Structure For Cloud Storage

Cloud storage has advantages of high scalability,no access restrictions,cheaper and easy management,which can make many small and medium enterprises and users get rid of the troubles of system construction and maintenance,it can reduce the cost of storage to users,so cloud storage has broad market prospects.Its appearance has completely changed the traditional concept of storage.Users store a large number of data in the cloud server,and lost the absolute control of the data at the same time,so cloud servers have become unreliable.In order to solve the problem of data security in the cloud,the researchers proposed to store the encrypted data in the cloud which can ensure the security of data,but it will lead to the problem of data sharing and efficiency.The searchable encryption is a kind of technology to support ciphertext retrieval,and the efficient and dynamic searchable encryption mechanism is a goal to the majority of researchers?The dynamic searchable encryption mechanism was proposed by Seny Kamara,the index was based on “keyword-file identifier”,created search arrays and delete arrays for dynamic operation.In this mechanism,the index space consumption is high and the search efficiency is low when the keyword set is large.The data structure in the mechanism involved is more at the time of updating,resulting process is more complex at the time of updating.This dissertation improved Seny Kamara's dynamic searchable encryption mechanism,which reduced the spatial consumption of the index and improved the search efficiency.In this mechanism,the index based on the “keyword-bit string” was firstly generated before the user uploads the data.Then the encrypted index and data files was uploaded to the cloud server.The user generated the retrieval token locally in retrieval time,and send the token of the corresponding file to user.At the time of updating,the corresponding add and delete tokens are generated,and the cloud server updates the service according to the given algorithm.The index structure of“keyword-bit string” can reduce the storage space and improve the search efficiency,and has better dynamic.The security and feasibility of the scheme are proved by the security analysis and experiment.The dissertation also studied the multi-thread encryption and decryption.Combined with multithreading technology,in this dissertation we will apply themulti thread encryption and decryption technology to the cloud storage system.In order to improve the efficiency of encryption and decryption in the process of user upload and download files.The experimental results show that the efficiency of this scheme is much higher than that of serial processing,and apply it to the cloud storage system.