| Along with the continuous development of Internet technology and increasement of information needed to be processed, the database security is becoming more and more important. The original data in one database is usually stored as the form of plaintext, which can be stolen by attackers easily. Recently, the encryption technology is one of the efficient methods to protect sensitive date. But the database encryption will affect the performance of the system, and some query operations can not be executed directly in the ciphertext. Therefor, a safe and efficient solution needs to be presented.Firstly, the key technology of database encryption, including the selection of encryption granulation, encryption layers and the algorithms, and key management, is introduced. Secondly, the OPES is deeply analyzed, and the MOES is presented in this thesis based on OPES. Its performance is also analyzed. MOES is modified in encryption data type, the selection of target function, bucket partition and repeated data processing. The modified algorithm can encrypt to both of numeric data and character data. And the repeated data is hidden in the phase of plaintext tiling. Therefore the encryption effect is improved.Finally, MOES algorithm is applied into the database encryption engine of a bid system. Combined with identify and the key management technology, a complete security framework of a bid system is produced. This framework can improve the data security in the reasonable system response time which can be accepted by users. |
