fn recent years, a method for analyzing security protocols wing the process algebra CSP [8] and its model checker FLIR [26] has been developed. This technique has proved successful, and has been used to discover a number of attacks upon protocols. However, the technique has required producing a CSP description of the protocol by hand; this has proved tedious and error-prone. In this paper we describe Gasper, a program that automatically produces the CSP description from a more abstract description, thus greatly simplifying the modelling and analysis process.