Abstract
This paper presents a general approach for analysis and veri cation of authentication properties in the language of Communicating Sequential Processes CSP It is il lustrated by an examination of the Needham Schroeder public key protocol The contribution of this paper is to develop a speci c theory appropriate to the analy sis of authentication protocols built on top of the gen eral CSP semantic framework This approach aims to combine the ability to express such protocols in a natu ral and precise way with the facility to reason formally about the properties they exhibit