Description:This book constitutes the thoroughly refereed post-proceedings of the First International Conference on Formal Aspects of Security, FASec 2002, held in London, UK, in December 2002.The 11 revised full papers presented together with 7 invited contributions were carefully reviewed, selected, and improved for inclusion in the book. The papers are organized in topical sections on protocol verification, analysis of protocols, security modelling and reasoning, and intrusion detection systems and liveness.