Application And Research Of Homomorphic Encryption In Cloud Storage Security

With the development and popularization of cloud computing, more and more users store their critical data in the cloud,the security of the cloud storage is becoming increasingly important. Encrypting user data and storing user data to the cloud in the form of ciphertext can ensure the security of user data in the cloud. Homomorphism encryption technology can directly operates and statistics the ciphertext information, the processing result and the result of operating the plaintext directly are the same. Therefore we can apply homomorphism encryption technology to encrypt user data in the cloud. By this way, we can not only ensure the security of user data in the cloud, but we can also improve the efficiency of the ciphertext retrieval.On the basis of the existing several homomorphic encryption algorithms, this thesis proposes an improved integer homomorphic encryption algorithm. In addition, this thesis combines the homomorphism encryption technology and vector space model technology based on TF-IDF and presents an improved homomorphism ciphertext retrieval scheme. The scheme is divided into four steps. The first stage is to estabilish the inverted index file. The second stage is to estabilish the retrieval file. The third stage where its main duty is to retrieve data. The four stage where its main duty is to download file.Finally, on the basis of the above research, this thesis implements a homomorphism ciphertext retrieval system. The simulation results show that the system does not only guarantee the security of user data in the cloud, but it also well completes the ciphertext retrieval task in the homomorphism environment.