Ciphertext Full Text Retrieval Of Cloud Database Based On Multiple Security Levels

In recent years,cloud storage technology develop rapidly.And cloud storage continue to attract more and more users and businesses with its mass storage,flexible management,low prices and many other features.But with the development of cloud storage technology many problems related to cloud data security issues are constantly exposed to us.It is necessary to encrypt the data in order to ensure the security of the cloud storage data.How fast and efficient retrieval of cloud-encrypted data becomes a hot issue.There are many shortcomings in the existing ciphertext full-text retrieval technology applied to the cloud database.By improving the inverted index and proposed a safe and efficient index structure and stored in the form of data tables in the cloud database.The improved index structure encrypts the attributes in the index table and stores the index in a special way to save storage space.Based on the improved index structure,the retrieval results are sorted by the method of keyword weight and spatial vector model.Users in system are generally have the characteristics of multi-security level.Based on the improved inverted index,a database hierarchical key management strategy is proposed.The data of different security levels are encrypted with different hierarchical key.The local server is responsible for the management of the key,effectively guarantee the security of the key.Index data and documents data use different encryption methods and encryption keys.Then the security of the system are further increased.Finally,based on the above theoretical research,this paper designed and implements a system about full-text ciphertext retrieval in cloud database based on multi-security level.And the system is tested and analyzed.