Analysis and implementation method of program to detect inappropriate information leak

For a program which handles secret information, it is very important to prevent inappropriate information leaks from a program with secret data. D.E. Denning (1976) proposed a mechanism to certify the security of program by statically analyzing information flow, and S. Kuninobu et al. (2000) proposed a more practical analysis framework including recursive procedure handling, although no implementation has been yet made. We propose a method of security analysis implementation, and show a security analysis tool implemented for a procedural language. We extend Kuninobu's algorithm by devising various techniques for analysis of practical programs that have recursive calls and global variables. This method is validated by applying our tools to a simple credit card program, and we confirm that the validation of program security is very useful.