Abstract: We proposed an approach for analyzing information-flow security of imperative language with output channels. The program is abstracted with pushdown system, which is then self-composed in order to adapt noninterference as a safety property. The output operations in the two relevant runs are respectively modeled as storing and matching procedure by pushdown rules. Then the termination-insensitive noninterference is verified by a reachability analysis of illegal-flow state. A variation of this approach can deal with program containing divergent run. An upper-bound regression algorithm was proposed to find the maximum upper-bound in order to trigger coercive termination of divergent run. The experimental results show that the approach is more precise and efficient than existing work.

Key words: Information f1ow,Noninterference,Pushdown system,Reachability analysis