Modeling and Analyzing Timed Security Protocols Using Extended Timed CSP

Security protocols are hard to design, even under the assumption of perfect cryptography. This is especially true when a protocol involves different timing aspects such as timestamps, timeout, delays and a set of timing constraints. In this paper, we propose a methodology for modeling and analyzing security protocols that are aware of timing aspects. We develop a formalism for modeling security protocols by extending Timed CSP with the capability of stating complicated timing behaviors for processes and events. A reasoning mechanism for the proposed formalism is developed based on Constraint Logic Programming (CLP). Using the reasoning engine built in CLP, the authentication properties of timed security protocols are able to be verified and attacks can be discovered. We demonstrate the capability of our method by modeling and verifying real-world security protocols. New approaches of using timing information to unfold and prevent potential attacks are also presented.