Research On The Cipher Text Retrieval And Access Control Technologies Of Cloud Storage System

With the rapid development of Internet, the user's private data become more and more difficult to manage. People's demand for information storage and management is not using the traditional local storage strategy can satisfy, the cloud storage system can better solve this problem. When users to store private data is very big, you need to encrypt the data of cipher text retrieval. Cloud storage is another important function in the user data sharing, but the cipher text data sharing once control improper will cause leakage of users' information, so we need the cipher text data access control.This thesis focuses on the homomorphic encryption algorithm, inverted index structure and access control scheme, the specifics as follow:(1) In the light of the problem of data encryption, the present thesis provided a homomorphic encryption scheme. Homomorphic encryption scheme can be found in the data encryption cipher data under the condition of some operations, with operation results being automatically encrypted, and the characteristics of homomorphic encryption can be used in cipher text retrieval. We provide a scheme of the improved homomorphic encryption algorithm, called Mod Q Retrieval Homomorphic Encryption algorithm(MQR), is used to solve the problem of safety in the DGHV algorithm and the CAFED algorithm due to retrieve.(2) Aiming at the problem of the efficient retrieval of cipher text, the thesis provided an improved full-text index structure. In the original inverted index structure reform step by step, wherein the inverted index is constructed on the basis of the encrypted vocabulary entry against the attack of semantic analysis, the partitioning encryption mechanism and two-level index structure thereof ensure the balance between security and efficiency.(3) To solve the safety issues in cloud storage for cipher text data sharing, and based on the CP-ABE algorithm. According to access control and related architecture, we designed the corresponding safety data structure, which can ensure the cipher text data secure sharing of the cloud storage system in an open environment.In the end, this thesis use the C/S model to design a cloud storage system experimental platform, and the requirements analysis of the system in detail, module design and so on. And we tested the retrieval efficiency of the cipher text data, wherein the excellent balance between efficiency and security of the scheme is proved.