Modelling and Verification of Layered Security Protocols: A Bank Application

Designing security-critical systems correctly is very difficult and there are many examples of weaknesses arising in practice. A particular challenge lies in the development of layered security protocols motivated by the need to combine existing or specifically designed protocols that each enforce a particular security requirement. Although appealing from a practical point of view, this approach raises the difficult question of the security properties guaranteed by the combined layered protocols, as opposed to each protocol in isolation. In this work, we apply a method for facilitating the development of trustworthy security-critical systems using the computer-aided systems engineering tool AutoFocus to the particular problem of layered security protocols. We explain our method at the example of a banking application which is currently under development by a major German bank and is about to be put to commercial use.