A consideration of the modes of operation for secure systems

Abstract

Secure systems are often characterised by a ‘mode of operation’. This acts as a shorthand for the degree of risk to the information on the system and the minimum security functionality required as a countermeasure. This paper examines the UK definitions of these modes and proposes a model of a system which can be used to capture the distinctions between them. The variations of possible secure system functionality within each mode are then discussed. Some new definitions, which are orthogonal to the modes of operation, are proposed which can be used to resolve ambiguities.