In this article we show how to model a range of notions in the context of delegation and revocation applied to security scenarios. We demonstrate how a range of delegation–revocation models and policies may be represented in pictorial form and formally represented in terms of reactive Kripke models and a first-order policy specification language. We translate first-order representations of our reactive Kripke models into an equivalent Answer Set Programming form that enables users to apply flexibly well-defined definitions of predicates to represent their requirements in terms of delegation–revocation policy specification.

The paper introduces a framework based on constructive conditional logics to define axiomatization, semantics and proof methods for access control logics. We formalize the well-known says operator as a conditional normal modality and, by considering some specific ombinations of access control axioms, we define four access control logics, namely, CondACLUC⁠, CondACLU4⁠, CondACLIC and CondACLI4⁠. Such logics integrate access control logics with intuitionistic conditional logics and provide a natural formulation of Boolean principals. The well-known 'speaks for' operator introduced in the logic ABLP is defined on the top of the says modality. We provide a Kripke model semantics for the logics and we prove that their axiomatization is sound and complete with respect to the semantics. Also, we develop sound, complete, cut-free sequent calculi for them. For the logic CondACLUC⁠, which (as concerns atomic principals) is slightly stronger than the logic ICL recently introduced by Garg and Abadi, we also provide a terminating sequent calculus, thus proving that the logic is decidable and that validity in CondACLUC is in PSPACE.

We show that Kripke semantics of modal logic, manifest in the syntactic proof formalism of labeled sequent calculi, can be used to solve three central problems in access control: Generating evidence for denial of access (counter model generation), finding all consequences of a policy (saturation) and determining which additional credentials will allow an access (abduction). At the core of our work is a single, non-trivial, counter model producing decision procedure for a specific access control logic. The procedure is based on backwards search in a labeled sequent calculus for the logic. Modifications of the calculus yield a procedure for abduction and, surprisingly, for saturation.

A novel countermodel-producing decision procedure that applies to several multi-modal logics, both intuitionistic and classical, is presented. Based on backwards search in labeled sequent calculi, the procedure employs a novel termination condition and countermodel construction. Using the procedure, it is argued that multi-modal variants of several classical and intuitionistic logics including K, T, K4, S4 and their combinations with D are decidable and have the finite model property. At least in the intuitionistic multi-modal case, the decidability results are new. It is further shown that the countermodels produced by the procedure, starting from a set of hypotheses and no goals, characterize the atomic formulas provable from the hypotheses.

We describe an approach that aims to unify certain aspects of access control and privacy. Our unified approach is based on the idea of axiomatizing access control in general terms. We show how multiple access control and privacy models and policies can be uniformly represented as particular logical theories in our axiom system. We show that our approach translates into different practical languages for implementation and we give some performance measures for some candidate implementations of our approach.

We introduce and study higher-order coalition logic, a multi modal monadic second-order logic with operators [{x}ψ]φ expressing that the coalition of all agents satisfying ψ(x) can achieve a state in which φ holds. We use neighborhood semantics to model extensive games of perfect information with simultaneous actions and we provide a framework reasoning about agents in the same way as it is reasoning about their abilities. We illustrate higher-order coalition logic to represent and reason about coalition formation and cooperation, we show a more general and expressive way to quantify over coalitions than quantified coalition logic, we give an axiomatization and prove completeness.

We define an Intuitionistic Conditional Logic for Access Control called CICL. The logic CICLis based on a conditional language allowing principals to be defined as arbitrary formulas and it includes few uncontroversial axioms of access control logics. We provide an axiomatization and a Kripke model semantics for the logic CICL, and we prove that the axiomatization is sound and complete with respect to the semantics.