A logic for reasoning about security

A formal framework called security logic (SL) is developed for specifying and reasoning about security policies, and for verifying that system designs adhere to such policies. Included in this framework is a definition of knowledge based on modal logic so that properties can be time-related, a definition of permission, and a definition of obligation. Permission is used to specify secrecy policies, and obligation is used to specify integrity policies. A security policy is given as a set of policy constraints on the SL model. The combination of policies is addressed. Examples based on policies from the current literature are given