Mode security: an infrastructure for covert channel suppression

The paper discusses a theory of covert channels called mode security. The general idea is to organize the state transitions of a multilevel state machine into distinct sets called modes. Roughly speaking, each machine mode is totally secure when considered in isolation of all other modes. Covert channels can therefore only occur when the machine executes a mode change decision; thus the name, mode security. The claim that all covert channels in a mode secure system are connected with mode change decisions can be satisfied by a generalization of the Turing test model of non-information flow