Towards a formal analysis of control systems

Electronic commerce became a buzzword when electronic net-works gained popularity, in particular of course due to the in-ternet. The security problem increases rapidly now that com-puter systems become more open. Most research on electronic commerce, and electronic data interchange in general, has fo-cussed on technical instead of organizational problems, such as value added networks, trusted third parties, chip cards, electronic signatures, etc. Computer science has been push-ing technology. However, these technical issues are not the bottleneck for acceptance of these new technologies. Success factors of introducing electronic commerce are solutions of the organizational problems, and the closely related legal issues. Formal models of electronic commerce represent and rea-son about security policies [4], for example for fraud detection and prevention. Computer security can be based on cryptog