A prototype B3 trusted X Window System

Multilevel secure windowing systems are a key technology for the 1990s. The authors have spent 20 months designing and implementing a prototype of a multilevel secure X Window System as a proof of concept vehicle for their software engineering process model for the development of trusted systems. The prototype is targeted to B3 evaluation criteria. In the early stages many doubted that B3 was achievable for a windowing system (especially X); the prototype demonstrates that B3 is achievable. The paper describes the goals, the architecture of the system, and some of the trade-offs made to achieve the goals. It also contrasts the work with existing compartmented mode workstations (CMW) windowing systems