Physical security technology is being used more often to protect the integrity of computing systems and the assets they contain. A physical security rating system is defined in terms of the difficulty of mounting a successful physical attack against it, quality assurance documentation and system testing. An evaluation system is presented for determining adequate physical security, as a function of the environment in which the system is placed and the value of the assets resident in the system.>

Open systems, now common in many small computers, have given the user logical access to all parts of his or her system. At the same time, the computing environment is moving out of the computing center and into the office and home, giving users physical access to their systems. This movement of the computing environment necessitates a mechanism to prevent the user from physically accessing certain parts of his or her system if logical security (of the type which limits the user's ability to make copies, change code, etc.) is to be reliable. This paper describes the development of a physical security system for protecting electronic circuits from unauthorized access. This system can be used to ensure that logical security mechanisms will remain uncompromised. The requirements, design criteria, and implementation of the system are discussed with an orientation towards practicality and manufacturing.