Research And Implementation Of User-Defined Data Type Of The Secure DBMS

Security techniques for database has been a focus in the research field of database. Although there are many high security Database Management Systems(DBMS), requirements in new application areas rapidly increased. Considering the limitation of traditional relational database management(RDBMS), object-relational database management(ORDBMS) is becoming an important issue in the research field of database. The project studies the techniques of design and implementation of user-defined data type(UDT) in SDM3, which is a homemade DBMS including Multilevel Secure model.The UDT introduced into SDM3 is divided into column type and row type. We can define relational table including column type and object table based on row type structure. According to UDT, we extend the SQL(Structured Query Language) in three aspects: data-control language, data-defined language and data-manipulated language. On the basis of data dictionary system in SDM3, we add the control structure, definition structure, message structure, lock structure related to UDT and realize some relevant operations on them. We discuss storage strategy for the objects, object id(OID), inheritance mechanism, column objects in relational tables and row objects in object tables.In order to effectively maintain the security of DBMS, we discuss the security control strategy used on UDT according to the security standard of B1 level and the features of SDM3. We set three kind of users: DBA, RESOURCE and CONNECT of SDM3 the relevant privileges operating on UDT, add the security levels of UDT, column objects in relational table and row objects in object table respectively. Farther, we analyse the covert channels caused by UDT's introduction, that is data dictionary covert channel and integrity restriction covert channel. Finally, we propose the appropriate solutions to these two kinds of covert channels.