When Diverse Firewall Design was employed to configure a firewall rule set, multiple teams, who got the same requirement specification of the firewall rule set, independently configured different versions of the rule set. And then rule sets comparing algorithms could be employed to decide whether multiple rule sets were equal or not. However, the performance of the present algorithm was not very good. A rule sets comparing algorithm based on rules intersection was proposed by this paper. First, rule conflicts resolving was employed to eliminate conflicts among rule sets. And then the problem of rule sets comparing was transformed into the problem of pictures comparing in multi-dimensional space. At last, the algorithm proposed by this paper compared the areas and the color of pictures to decide the rule sets were equal or not by employing rules intersection. The results of experiments not only showed that the algorithm could find out all discrepancies among rule sets, but also verified that the performance of the algorithm was better than that of the present algorithm.
