Graphical descriptions of security protocols

We present a graphical approach to security protocol representation. Protocol runs canbeviewedasMessage Sequence Charts. Message Sequence Charts are an appropriate graphical representation of security protocols. We show how sequence charts can be constructed from protocol runs of a broad range of processes in the Security Protocol Language (SPL). In their graphical form, Message Sequence Charts make the behaviour of a protocol easier to understand. They are particularly valuable when runs exhibit undesired behaviour, where they can give a concise account on how to attack protocol weaknesses. The relation between MSCs and SPL process runs is at the basis of the protocol visualization capabilities of the χ-Sim tool. The tool allows developers to simulate protocols programmed in an implementation of SPL. The resulting runs can be rendered graphically as MSCs. Key words: Security Protocols, Message Sequence Charts.