Design Proposal for a Highly Robust Peripheral Input Device Switch for a Multi-Level Secure System

A number of commercial vendors have tried to develop peripheral input device switches to provide high robustness, but most fail to achieve the assurance level necessary for use in a multi-level secure system. This paper provides the groundwork for designing a highly robust peripheral input device switch for Universal Serial Bus USB keyboards and mice by defining the requirements, the external and internal interfaces, the data flows, and the state diagrams of the switch. All of these are used to show that only a single computer connected to the switch is allowed to communicate with the attached keyboard and mouse at any given point in time, that a Flush command must precede any connection between an attached computer and the keyboard and mouse, and that no two CPPs are allowed to communicate with each other through the switch.