Research On Multi-user Symmetric Searchable Encryption Scheme Satisfying Forward Security

Searchable encryption is a new and efficient retrieval technology,which is characterized by realizing ciphertext data search on the basis of ensuring cloud data encryption.With the development of searchable encryption technology,scholars at home and abroad have achieved fruitful results in search efficiency and usage scenarios.However,with the continuous generation of local data,users hope to dynamically update cloud data.For this reason,domestic and foreign scholars have proposed searchable encryption schemes that support dynamic updates.However,the latest research shows that existing dynamic searchable encryption schemes have security vulnerabilities and may encounter injection attacks from adversaries.Therefore,it is necessary to study a more secure symmetric searchable encryption scheme in dynamic update scenarios.Based on the encrypted data in cloud storage,this thesis studies symmetric searchable encryption technology in order to achieve a more secure searchable encryption scheme.The main work completed in the thesis is as follows:(1)Combined with the space vector model,a dynamic symmetric searchable encryption scheme based on semantic grouping is proposed.First,it is raised to construct a semantic grouping balanced binary tree as an index structure,which reduces the number of nodes visited during search and improves search efficiency through semantic grouping.Then combined with the idea of partition matrix,a new document update method is putted forward.This method rebuilds the matrix for newly added keywords and adds virtual keywords to ensure the security during the update,so as to avoid the leakage of the relevance between the newly added documents and the keywords during the update.Finally,the correctness of the scheme is analyzed to verify the feasibility of the scheme,and the safety of the scheme is proved by building a safe simulation game.(2)Aiming at the security threats caused by malicious servers,a forward-secure symmetric searchable encryption scheme with verifiable results is proposed.Different from the previous dynamic symmetric searchable encryption schemes,which assume that the server is honest and credible,this scheme focuses on the security of searchable encryption schemes under the malicious server model.First,a new result validator construction mechanism is raised,which uses the verifiable characteristics of pseudo-random functions to generate binding tags for the index structure to solve the problem of validating the search results of malicious servers.Then combined with the trapdoor one-way transfer technology to ensure that the trapdoor is irreversible,so that the scheme meets forward safety.Next,the algebraic pseudo-random function is used to replace the pseudo-random function to reduce the additional storage overhead generated by the client to save the state information.Finally,formal analysis proves that the scheme has higher security.(3)Aiming at the multi-user scenario of symmetric searchable encryption,this paper brings forward a dynamic multi-user forward secure symmetric searchable encryption scheme.This program focuses on the study of multi-user access control and forward security issues.First,a user encryption and decryption key and an auxiliary encryption and decryption key are generated for each user through the key distribution technology.The search and decryption process requires the coordination of two keys to complete.Different from the single-user forward security searchable encrypted state information storage strategy,this solution introduces a trusted third-party server to store the state information and supports the verification of the user's identity.The trapdoor structure must be completed by the data user and a trusted third-party server to ensure the forward security of the solution.Finally,through the analysis of the scheme,it is proved that the scheme still has higher efficiency while ensuring higher security.