Research On Multi-Keyword Fuzzy Searchable Encryption Mechanism Over Cloud Storage

With the advent of the era of cloud computing,more and more enterprises and indi-viduals choose to outsource the storage and management of their data to cloud to reduce their local management costs.However,private data must be encrypted before uploaded to avoid data leakage and abuse,meanwhile,essential data management including ef-ficient keyword searching is necessary.Although the encryption of data increases the difficulty of data management,searchable encryption ensures the cloud server can still search over the encrupted data.And with the continuous development of the concept of sharing,searchable encryption is no longer limited to search over personal data,but other authorized users can also search the data shared in cloud.However,the existing schemes for multi-user scenario generally have the problem of high computation and communication overhead.Moreover,errors in the keywords are unavoidable in the real world,which may make SE not return correct results.Although some schemes have been proposed in terms of fuzzy searchable encryption,they still have many problems,such as low accuracy and low error tolerance for fuzzy search.We analyze the security strenth of our scheme,and evaluate the performance by conducting experiments,which shows that our scheme has higher accuracy,higher error tolerance,and less computa-tional overhead while ensuring confidentiality,indistinguishability of query and privacy preservation.Therefore,aiming at the different requirements of symmetric searchable encryp-tion and public key encryption with keyword search,we propose searchable encryption scheme supporting multi-keyword fuzzy search in multi-user scenario.The main con-tributions of this paper are as follows:Firstly,Based on public key encryption with keyword search,we propose an ef-ficient multi-user multi-keyword fuzzy search scheme over encrypted cloud storage.Specifically,We design a novel data transformation method by introducing permuterm index to make our scheme have a high degree of error tolerance and support wildcard query.Besides,in order to avoid the sharp decrease of accuracy caused by the increase in the number of fuzzy keywords in multi-keyword scenario,our scheme stores the sub-strings to bloom filter directly and distinguishes substrings by using keyword length as a mark.Meanwhile,by applying an improved secure KNN where cloud server will re-encrypt owners' data and users' queries,our scheme largely reduce the computational overhead of users in multi-user scenario.Secondly,symmetric searchable encryption scheme has the advantages of low computational cost,but it is more suitable for single user scenario.In order to better ap-ply symmetric searchable encryption to multi-user scenario,this paper proposes a sym-metric searchable encryption scheme with high efficiency and security in multi-user sce-nario.By re-encrypting users' encrypted query,our scheme supports non-key-sharing multi-user searchable encryption,and effectively reduces users'computing overhead.In addition,we introduce the concept of fuzzy search to improve scheme's applicability.By keyword transformation,our scheme ensure that the fuzzy keywords and accurate keywords can be stored in a unified form,and improve the accuracy of wildcard query by improving LSH hash function.Experimental results show that our scheme signif-icantly reduces users' computation and communication overhead,and can effectively solve fuzzy search including wildcard query.