Petri nets for the verification of Ubiquitous Systems with Transient Secure Association

Transient Secure Association has been widely accepted as a possible alternative to traditional authentication in the context of Ubiquitous Computing. In this paper we develop a formal model for the Resurrecting Duckling Policy that implements it. Our model, that we call TSA systems, is based on Petri Nets, thus obtaining an amenable graphical representation of our systems. We prove that TSA specifications have the same expressive power as P/T nets, so that coverability, that can be used to specify security properties in this setting, is decidable for TSA systems. Then we address the problem of implementing TSA systems with a lower level model that only relies on the secure exchange of secret keys. We prove that if we view these systems as closed systems then our implementation is still equivalent to P/T nets. However, if we consider an open framework then we need a mechanism of fresh name creation to get a correct implementation. This last model is not equivalent to P/T nets, but the coverability problem is still decidable for them, even in an open setting, so that checking the security properties of the represented systems remains decidable