Security Types for Mobile Safe Ambients

The Ambient Calculus and the Safe Ambient Calculus have been recently successfully proposed as models for the Web. They are based on the notions of ambient movement and ambient opening. Different type disciplines have been devised for them in order to avoid un-wanted behaviours of processes. In the present paper we propose a type discipline for safe mobile ambi-ents which is essentially motivated by ensuring security properties. We associate security levels to ambients and we require that an ambient at security level s can only be traversed or opened by ambients at security level at least s. Since the movement and opening rights can be unrelated, we consider two partial orders between security levels. We also discuss some meaningful examples of use of our type discipline.