Evolution of a trusted B3 window system prototype

The early issues, obstacles, and ultimate achievements of Phase II of the US DARPA Advanced Computing Systems project to develop a proof-of-concept prototype for a B3 X-Window system on a TMach base are described. The present work defines initial project goals, presents an overview of X, and describes system objectives. The major implications of meeting the B3 trust criteria and the constraints of building the Trusted X prototype on the TMach system (itself a prototype) are described. The reader is led through the process of Trusted X evolution from an initial architecture requiring a large and complex TCB to an architecture based on task polyinstantiation greatly simplifying the TCB