Research On The Query Techniques Based On Encrypted XML Data

With the explosive growth of the internet, networking and computing technologies over the past decade, the software industry has witnessed the emergence of the software as a service paradigm. Motivated by the software as a service, recent database research has explored the viability of the "database as a service" (DAS) paradigm. The techniques to query encrypted XML data are applied in DAS architectures, where a client may outsource data to a service provider that provides data management services. Security is of paramount concern, as the service provider itself may be untrusted. Encryption offers a natural solution to preserve the confidentiality of the client's data. The challenge now is to execute queries over the encrypted data, without decrypting them at the server side.In this thesis, we develop a solution of query processing against encrypted XML data. The solution relies on the Query-Aware Decryption applied in [10] by J.G. Lee and K.Y. Whang. Query-Aware Decryption allows us to decrypt only those parts that would contribute to the query result. Here we give a solution, which applies the one-way property of Hash function to solve the distribution of user keys, and disseminates an encrypted XML index along with the encrypted XML data. As the decrypted index informs us where the query results are located in the encrypted XML data, the unnecessary decryption can be prevented for other parts of the data. Then, we prove that dissemination of the encrypted XML index and user key index does not compromise security. Finally, a prototype of our solution is implemented in the environment of JAVA. The experimental results show that our method improves the performance of query processing, efficiently avoides decrypting non-relative data, subtly reduces the amount of user keys exchange and solves the dissemination of user keys.