Constraints solution for time sensitive security protocols

With the development of network and distributed systems, more and more security protocols rely heavily on time stamps, which are taken into account by a few formal methods. Generally, these methods use constraints to describe the characteristic of time variables. However, few of them give a feasible solution to the corresponding constraints solving problem. An effective framework to model and verify time sensitive security protocols is introduced in [1], which doesn't give an automatic algorithm for constraints solution. In this paper, an effective method is presented to determine whether the constraints system has a solution, and then implemented in our verifying tool SPVT. Finally, Denning-Sacco protocol is taken as an example to show that security protocols with time constraints can be modeled naturally and verified automatically and efficiently in our models.