Research On Forward And Backward Security For Searching Technology Over Encrypted Cloud Data

Searchable encryption(SE)is a new type of ciphertext retrieval technology with high efficiency,which not only protect the privacy of data but also support searching on encrypted data.With the emergence of this technology,it can well protect the privacy of user data outsourced in cloud,preventing the risk of information leakage,and protecting the privacy security of user.Recently,however,the study has shown that SE has the drawback attacked from the adversary.Therefore,it is necessary to study SE schemes with more security than before.Based on the encrypted data in cloud storage,this dissertation studies the topic of privacy protection schemes for SE technology in order to achieve more secure SE schemes.In this process of studying,this dissertation proposes two schemes to solve the problem encountered in the research.(1)A forward security SE scheme for cloud data is proposed.SE is a kind of very practical technology,protecting the privacy of data outsourced in cloud,and searching on encrypted data.However,the file injection attack with efficient and accurate causes a serious threat to the security of SE schemes.This dissertation proposes an SE scheme with forward security.The scheme uses the chameleon hash function to establish the query trapdoor,using the random numbers to replace the query keywords,which protects the search process and hides the relationship between the newly added files and the keywords that have been queried.In addition,the scheme uses the Bloom Filter to establish file vector realizing the multi-keyword query.(2)A backward security SE scheme for cloud data is proposed.During the update process,if the data is deleted directly,the cloud may obtain the important information.The connection will be leaked between keywords and files.Therefore,the adversary can attack SE schemes from the leaked information for recovering the ciphertext.This dissertation proposes an SE scheme with backward security.Based on the first scheme,this dissertation proposes the SE scheme with backward security.The scheme uses the data structure of version control repository hiding the relationship between the newly added file and the keywords queried to achieve forward security.In addition,the scheme uses the symmetric puncturable encryption algorithm hiding the deleted information for files to achieve backward security.To improve the file integrity,the scheme also supports result validation.