A formal model to verify authentication protocols with timeout strategy

We propose a formal model to verify authentication protocols with timeout strategy. After investigating a state-of-the-art model checker named SATMC, the connotative time involved in the rule labels is revealed and utilized, which allows us to re-evaluate the security of authentication protocols with timeout strategy. We illustrate our model by analyzing the security of NSPK protocol. Finally, the verification results of a set of well-known authentication protocols are given.