Specifications for Multi-Level Security and a Hook-Up

In this paper, we give a brief description of several formalisms for computer security, and discuss some of the problems in their interpretation and application. We define the property of "hook-up security", which can be shown to imply that a collection of hook-up secure systems can be hooked up to form a secure complex system. We believe this result addresses some of the problems with other definitions of security, and will be valuable in the design of large secure systems from simpler secure components.