Peter Ryan has over 15 years experience in cryptography and mathematical modelling, computer security and formal methods, gained at GCHQ, CESG, DERA and SRI Cambridge. He is a DERA Fellow, an IMA Fellow and Chair of the Steering Committee of ESORICS. In 1999 he was awarded the title of DERA Fellow. Steve Schneider is a Senior Lecturer in the Department of Computer Science, Royal Holloway, University of London, UK. He has published a large number of journal and conference papers in the areas of concurrency theory and security. Michael Goldsmith is Managing Director of Formal Systems (Europe) Ltd, the company which developed the FDR tool and devised the techniques described in the book in collaboration with DERA and the University of Oxford. He is a Senior Research Fellow of Worcester College, Oxford. Gavin Lowe is a Lecturer in Computer Science at the University of Oxford. He was responsible for discovering the attack on the Needham-Schroeder Public-Key protocol, which established the power of the current approach. Bill Roscoe is Professor of Computing Science at the University of Oxford. He is one of the principal developers of CSP and of its application to cryptoprotocols and other aspects of computer security.