Multi-Level Security Based on Physical Distribution

We are interested in multi-level secure networks in which the host systems are required to conform to a multi-level security policy such that information is constrained to flow between hosts only in certain ways. The problem of interest is how to most efficiently block such flows in the face of the threat of untrusted software running on the communication sub-network processors and on all or some untrusted hosts. A model for secure transmission and a possible solution which we feel satisfies certain criteria are presented. The solution, however, relies on the assumption of a highly reliable sub-network. Consequently, it is likely to find application as a mechanism to implement multi-level security by inter-connecting, on a local network, untrusted hosts operating at different levels.