Specifying Multi-Level Security for an Embedded Real-Time Control System

Multi-level data security is a requirement in many of today's advanced, real-time embedded systems. Current approaches to meeting multi-level security requirements are based on expensive custom or proprietary hardware and software. However, real-time embedded systems are evolving towards open-system architectures and commercial off-the-shelf (COTS) hardware and software. It is therefore important to develop a standard method for evaluating the security aspects of real-time embedded systems, and for handling black-box COTS components in proprietary systems. This chapter presents a brief analysis of multi-level data security in the context of a simplified exemplary real-time, embedded avionics system and discusses mechanisms that can be used to solve the problem of integrating COTS components into a secure system. As is required of high assurance secure systems, a formal model of one such mechanism based on the use of a trusted network interface unit mechanism is provided using the LOTOS formal specification language.