Research On Multi-user Forward Secure Dynamic Searchable Symmetric Encryption

In recent years,with the continuous development of cloud computing,cloud storage services have become more and more popular among users.Users upload local data to the cloud server to reduce local storage pressure.However,this data may contain the user's private information,so the data needs to be encrypted before uploading.However,data encryption can make the user's query operation difficult.Therefore,searchable encryption technology is used to solve such problems.It not only supports the user's ability to retrieve data on encrypted data,but also protects the privacy of users' outsourced data.However,in the existing dynamic searchable encryption mechanism,when the user performs dynamic update of the documents,one problem named forward security is brought about,that is,information about the updated keyword is leaked.After these leaks are exploited by adaptive attacks,the user's query privacy will suffer devastating damage.In addition,most of the existing forward security solutions do not support multi-user queries or search results ranking.Thus,this paper studies forward security problem and search results ranking in dynamic searchable encryption mechanisms.Aiming at the problem of multi-user forward security in dynamic searchable encryption mechanism,an efficient multi-user forward-secure dynamic searchable encryption model is established and the corresponding detailed solution is proposed.The so-called forward security means that the cloud server cannot infer whether the newly added document contains keywords that have been searched before.This paper solves the problem of forward security by using keyword state information stored on the proxy server and a chain index stored on the cloud server,and using bilinear mapping knowledge to generate a pair of complementary keys to solve the problem of multi-user query.Through a large number of comparative experiments with the existing scheme — Sophos,the results show that the proposed algorithm outperforms the Sophos,which significantly improves the efficiency of searching and updating data.Aiming at the problem of sorting search results on the server side in the dynamic searchable encryption mechanism,a secure dynamic searchable encryption model that supports ranking is established,and the corresponding solution is proposed.The main idea of the scheme is to calculate the relevance score of each keyword in different documents according to each keyword's frequency that used in the field of information retrieval,map the scores to a finite integer field,and finally establish the corresponding secure index by using ORE-like technique.The scheme can not only efficiently retrieve the matching items satisfying the query conditions,but also improve the security of the underlying keyword relevance score information in the index,making it less vulnerable to statistical analysis attacks.Through the comparison experiments before and after,the results show that expanding the function of the search results ranking on the original scheme has little effect on the efficiency of searching and updating data,and the results are within the acceptable range.