William E. Boebert

Secure Ada Target: Issues, System Design, and Verification

The Secure Ada Target (SAT) machine is designed to meet or exceed the DoD requirements for multi-level secure systems. This paper describes the require-ments on such designs, our approach to meeting these requirements by introducing tagged objects, and a specialized tagged object processor (TOP) that handles all operations involving tagged objects. Basic system security is achieved using a small software kernel and the TOP. The structure of our proofs, such that the system satisfies appropriate security properties, will be outlined. Brief remarks concerning the implementation of user Ada programs on the SAT system conclude the paper. Our design approach is largely independent of CPU selection, though implementation details necessarily depend on the processor selection.

An Approach to the Specification of Distributed Software

In this paper we first characterize distributed systems. Next we survey recently proposed programming constructs designed to facilitate communication amongst software elements of a distributed system. We then give the basis of a methodology for the formal specification of distributed systems, and follow with an example to clarify the technique. We close with a discussion of necessary extensions to the methodology and a review of the objectives of specification.