A Distributed Secure System

We describe the design of a distributed general-purpose computing system that enforces a multilevel security policy. The system is composed of standard UNIX systems and small trustworthy security mechanisms linked together in such a way as to provide a total system which, is not only demonstrably secure, but also highly efficient and cost effective. Despite the heterogeneity of its components, the system as a whole appears to be a single multilevel secure UNIX system, since the fact that it is actually a distributed system is completely hidden from its users and their programs.This is achieved through the use of the "Newcastle Connection", a software subsystem that links together multiple UNIX or UNIX-look-alike systems, without requiring any changes to the source code of either the operating system or any user programs. Construction of a prototype implementation is in progress.