Towards Verification of the PANA Authentication and Authorisation Protocol using Coloured Petri Nets

The Extensible Authentication Protocol (EAP) allows a server to request authentication information from a client. In order to transport EAP messages over an IP network, the Protocol for Carrying Authentication for Network Access (PANA) has been developed. This paper applies a protocol engineering methodology using Coloured Petri nets (CPNs) as a step towards formally verifying the design of PANA. State space analysis of a simple PANA configuration shows that the current specification has removed deadlocks discovered in previous PANA versions. Furthermore, state space and language analysis of PANA for different client retransmission limits leads to two important conjectures: the state space size (number of nodes, arcs) can be expressed as a polynomial in terms of the retransmission limit; and the protocol language is independent of the retransmission limit. The results suggest parametric verification is applicable to PANA. Finally, ideas for automatically validating the CPN model against the original specification are discussed.