Research On Ciphertext Retrieval Technology In Cloud Storage Environment

The application and development of cloud storage makes more users choose to store data in the cloud.In order to protect the privacy of the data,the user stores the encrypted private data in the cloud.A large number of ciphertext data are stored on the cloud platforms.How to quickly query the data required by users from a large number of ciphertexts is an important issue that is urgently needed to be solved by cloud platforms.Because of its ability to search ciphertext directly,ciphertext retrieval technology has become a hot topic in the research of privacy security in cloud storage.The multi-keyword ranked searchable encryption(MRSE)scheme has become one of the most important research directions in the ciphertext retrieval field because of its advantages of great user experience and low communication cost.However,the existing MRSE schemes leak search mode and access mode by default and do not conform to the definition of the result order of multi-keyword retrieval semantics.Privacy leakage and low search accuracy hinder the practical application of MRSE.The multi-user retrieval scenario is common in practical applications.How to extend the MRSE scheme in the context of multi-user retrieval is a major problem that needs to be solved urgently.This paper proposes a corresponding optimization scheme for the problems of privacy leakage and low retrieval accuracy in the MRSE scheme.At the same time,a lightweight multi-user retrieval MRSE scheme is constructed under multiuser retrieval scenario.The main contents and contributions are shown as follows:(1)The idea of optimization is given aiming at the defects of privacy leakage and low retrieval accuracy existing in the MRSE schemes and a PR-SMSE scheme is proposed.This scheme generates trapdoors based on random numbers,which ensures the indistinguishability of the trapdoors and hides the search pattern;By adding faked keywords and random relevancy scores in the index as confusion improve index security;The access pattern is hided by separating store index and encrypted file set;Combining the semantics of multiple keyword retrieval gives the definition of the retrieval result prioritization and improves the retrieval accuracy.By analyzing the security of the PR-SMSE scheme,it is verified that this scheme can achieve the confidentiality of cloud storage ciphertext,indistinguishability of trapdoors,and security of access mode.Experimental results show that the algorithm efficiency of this scheme has obvious advantages compared with other schemes.(2)Considering the actual multi-user retrieval scenario,the existing ciphertext retrieval schemes that support multi-user retrieval have the drawbacks of high computational cost,key and user management reliance on trusted third parties,and high user cancellation costs.In order to solve these problems,this paper presents LM-MRSE scheme.This scheme removes trusted third parties and enables users to autonomously authorize;The Adoption of trusted agent mechanism reduce the computational burden on the user and achieve the user's anonymous query;By adding an authorized access table ensure the user's dynamic revocation and finegrained access control of files;Hash table is used to store legal user identity information and reduce the access control time complexity to O(1).Through the security analysis,it is verified that this scheme can satisfy the confidentiality of the cloud storage ciphertext,query security,and user revocation security.The LM-MRSE scheme does not involve exponential operations,and the access control time complexity is only O(1).Experimental results show that this scheme can achieve lightweight multi-user retrieval.