Model Checking Strategic Abilities in Information-sharing Systems

TL;DR

This paper introduces a new class of concurrent game structures with imperfect information, called A-cast systems, allowing for decidable model-checking of strategic abilities in complex information-sharing scenarios, including security applications.

Contribution

It defines A-cast systems with private data-sharing capabilities and proves decidability of model-checking a significant ATL fragment over these systems, enabling analysis of complex security protocols.

Findings

Decidability of model-checking ATL fragments over A-cast systems.

A-cast systems can encode security problems like terrorist-fraud attacks.

The framework generalizes architectures with information forks and broadcast communication.

Abstract

We introduce a subclass of concurrent game structures (CGS) with imperfect information in which agents are endowed with private data-sharing capabilities. Importantly, our CGSs are such that it is still decidable to model-check these CGSs against a relevant fragment of ATL. These systems can be thought as a generalisation of architectures allowing information forks, in the sense that, in the initial states of the system, we allow information forks from agents outside a given set A to agents inside this A. For this reason, together with the fact that the communication in our models underpins a specialised form of broadcast, we call our formalism A-cast systems. To underline, the fragment of ATL for which we show the model-checking problem to be decidable over A-cast is a large and significant one; it expresses coalitions over agents in any subset of the set A. Indeed, as we show, our systems and this ATL fragments can encode security problems that are notoriously hard to express faithfully: terrorist-fraud attacks in identity schemes.