Towards Operational Measures of Computer Security

摘要: Ideally, a measure of the security system should capture quantitatively intuitive notion 'the ability to resist attack'. That is, it be operational, reflecting degree which can expected remain free breaches under particular conditions operation (including attack). Instead, current levels at best merely reflect extensiveness safeguards introduced during design and development system. Whilst we might expect developed higher level than another exhibit 'more secure behaviour' in operation, this cannot guaranteed; more particularly, infer what actual behaviour will from knowledge such level. In paper discuss similarities between reliability with intention working towards measures 'operational security' similar those that have for systems. Very informally, these could involve expressions as rate occurrence (cf failures reliability), or probability specified 'mission' accomplished without breach function). This new approach is based on analogy failure breach. A number other analogies support view are introduced. We examine duality critically, identified important open questions need answered before quantitative taken further. The work described here therefore somewhat tentative, one our major intentions invite discussion about plausibility feasibility approach.