Multi-user Searchable Encryption Scheme Based On Encrypted Semantic Tree

With the continuous development of cloud computing,cloud storage has become one of the most widely used applications of cloud computing.While cloud storage brings convenience to users,it also creates problems that separation of data ownership and management rights.Cloud storage security has received widespread attention in the industry.In order to better solve those problems,the searchable encrypted cloud storage service mechanism and efficiency problem of searchable encryption have been widely studied and developed by researchers in recent years.This dissertation studies the inaccuracy of current searchable encryption,and achieves accurate searchable in semantics and efficiency.The current searchable encryption scheme has been studied for multi-user,multi-keyword search,etc.but those schemes do not consider the influence of semantics on search results.In order to solve this problem,this dissertation achieved semantic searchable encryption,and improves operational efficiency on this basis.This dissertation utilizes two cloud servers to ensure the efficient operation of users semantic search,one is to matches the trapdoor and generates the results which matching the related semantic,and the other one is to search for the most relevant files and return them to the user.In order to be safer and more efficient,in this dissertation the semantic tree was sent to the cloud server,we use the method that trapdoor produced in the cloud server to ensure the user's computational complexity is reduced,meanwhile the semantic tree is secured to ensure the security of the key information,not stolen by a malicious user.In addition,MD5(Message-Digest Algorithm 5)encryption can guarantee the correspondence between plaintext and ciphertext,and the ciphertext encrypted by MD5 cannot decryption to plaintext which is the feature of MD5 algorithm,ensuring the security of plaintext.Through the security analysis showed that the scheme has anti-forgery attack,security under known ciphertext model and data security.Compared with the calculation cost of the current schemes,it is shown that the proposed scheme is efficient.