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Analyzing the Intruder Role in Cryptographic Protocols

In this paper a method for analyzing the role of the intruder and automatic exploration of possible attack scenarios in cryptographic protocols is presented. In the presented method, the intruderʹs capability for eavesdropping the protocol messages and using them to masquerade the protocol principals by means of a set of inference capabilities is modeled. Furthermore, the existence of a proper attack strategy as a general capability of an intelligent intruder for designing the attack scenario is considered in the model. The intruder strategy is based on finding proper instances of the protocol execution as a source of obtaining necessary attack information. Two important properties of the cryptographic protocols (i.e. secrecy and authentication) can be analyzed using the presented method. To show the strength of the presented method, formal specification of the Woo-Lam authentication protocol and the way of finding an attack scenario against it is described as a sample.