Formal analysis of a fair payment protocol

We formally specify a payment protocol. This protocol is intended for fair exchange of time-sensitive data. Here the ?-CRL language is used to formalize the protocol. Fair exchange properties are expressed in the regular alternation-free ?-calculus. These properties are then verified using the finite state model checker from the CADP toolset. Proving fairness without resilient communication channels is impossible. We use the Dolev-Yao intruder, but since the conventional Dolev-Yao intruder violates this assumption, it is forced to comply to the resilient communication channel assumption.