Developing secure systems in a modular way

The authors present a new technique for development and verification of secure systems in a modular way. At the heart of the technique is a general approach for coping with the composition of modules. In abstract system design, this composition approach is applied to determine security of the overall system and then to produce appropriate security requirements for its modules in terms of functional specifications. These modular security requirements enable different modules to have different security properties. In concrete system design, only correspondences between the modular security requirements and source code of the modules need to be demonstrated to ensure that the final system is secure. To handle changes of functional specifications during system development, dependencies among modular security requirements are analyzed. These can be used to locate the modules affected by changes, and to avoid unnecessary security reevaluation of other modules