Covert Channel In The Safe Operation Of Systems Research

As the Tuling Sec OS 2.0/4 being the project background, this paper reports the research of covert channel analysis of security operating system. According to the covert channel analysis requirements in relevant information system evaluation criteria, after analyzing the features of different types of covert channel and features of different covert channel identification methods, we proposed a new identification method--modified semantic information flow method. This method has less workload, also can directly analyze on the source code base and exclude the false results, and can help the following covert channel handling. We used this method to identify the cover channels of the Tuling Sec OS, and used information-theory-based formal method to compute the bandwidth of identified channels, and handled the covert channels properly according to security policy by different means such as elimination, bandwidth limitation, audit, etc. This covert channel analysis result is conforming to the specification and requirement of Level 4 security operating system in relevant national standards.