Safety Verification of Communicating One-Counter Machines

In order to verify protocols that tag messages with integer values, we investigate the decidability of the reachability problem for systems of communicating one-counter machines. These systems consist of local one-counter machines that asynchronously communicate by exchanging the value of their counters via, a priori unbounded, Fifo channels. This model extends communicating finite-state machines (Cfsm) by infinite-state local processes and an infinite message alphabet. The main result of the paper is a complete characterization of the communication topologies that have a solvable reachability question. As already Cfsm exclude the possibility of automatic verification in presence of mutual communication, we also consider an under-approximative approach to the reachability problem, based on rendezvous synchronization. 1998 ACM Subject Classification F.1.1 Models of Computation, D.2.4 Program Verification