SCR: A Practical Approach to Building a High Assurance COMSEC System

To date, the tabular-based SCR (Software Cost Reduction) method has been applied mostly to the development of embedded control systems. This paper describes the successful application of the SCR method, including the SCR* toolset, to a di erent class of system, a COMSEC (Communications Security) device called CD that must correctly manage encrypted communications. The paper summarizes how the tools in SCR* were used to validate and to debug the SCR speci cation and to demonstrate that the speci cation satis es a set of critical security properties. The development of the CD speci cation involved many tools in SCR*: a speci cation editor, a consistency checker, a simulator, the TAME interface to the theorem prover PVS, and various other analysis tools. Our experience provides evidence that use of the SCR* toolset to develop high-quality requirements speci cations of moderately complex COMSEC systems is both practical and