Abstract: Owing to online DBMS is used widely, sensitive information stored in database should be encrypted. To acquire higher performance, a technology about privacy homomorphism can be used. By using this technology, it is possible to manipulate encrypted information without decrypting them. DBMS with multilevel secure mechanism would have higher information protection level. A new encryption scheme on online DBMS with multilevel secure mechanism is provided in this paper. The server has keys to handle data with all secure levels, and the client only has the key suiting for its own level. It includes two-layer encryption mechanism on fields and records. The process of encryption and decryption has clear layer and simple calculation. It has multilevel secure mechanism. High secure level users can decrypt low secure level data. It supports all relation operations on database. The example shows that the provided encryption scheme truly has feasible key configuration programme, right encryption and decryption process and perfectly supports multilevel secure mechanism.

Key words: online DBMS, homomorphic encryption, multilevel secure mechanism