This volume, like the symposium CSP25 which gave rise to it, commemorates the semi-jubilee of Communicating Sequential Processes. 1 Tony Hoare s paper Communicating Sequential Processes is today widely regarded as one of the most in?uential papers in computer science. To comm- orate it, an event was organized under the auspices of BCS-FACS (the British Computer Society s Formal Aspects of Computing Science specialist group). CSP25 was one of a series of such events organized to highlight the use of formal methods, emphasize their relevance to modern computing and promote their wider application. BCS-FACS is proud that Tony Hoare presented his original ideas on CSP at one of its ?rst meetings, in 1978. The two-day event, 7 8 July 2004, was hosted by London South Bank U- versity s Institute for Computing Research, Faculty of Business, Computing and Information Management. The intention was to celebrate, re?ect upon and look beyondthe?rstquarter-centuryofCSP scontributionstocomputerscience. The meeting examined the impact of CSP on many areas stretching from semantics (mathematical models for understanding concurrency and communications) and logic(forreasoningaboutbehavior), throughthedesignofparallelprogramming languages (i/o, parallelism, synchronization and threads) to applications va- ing from distributed software and parallel computing to information security, Web services and concurrent hardware circuits. It included a panel discussion with panelists Brookes, Hoare, de Roever and Roscoe (chaired by Je? Sanders), poster presentations by PhD students and others, featured a ?re alarm (requ- ing evacuation in the rain ) and concluded with the presentation of a fountain pen to Prof. Sir C. A. R. Hoare."

Preface Formal Aspects of Security (FASec) was held at Royal Holloway, University of London, 18-20 December 2002. The occasion celebrated a Jubilee, namely the 25thanniversaryoftheestablishmentofBCS-FACS, theFormalAspectsofC- puting Science specialist group of the British Computer Society. FASec is one of a series of events organized by BCS-FACS to highlight the use of formal me- ods, emphasize their relevance to modern computing, and promote their wider application. As the architecture model of information systems evolves from - connected PCs, throughintranet (LAN) and internet (WAN), to mobile internet and grids, security becomes increasingly critical to all walks of society: c- merce, ?nance, health, transport, defence and science. It is no surprise therefore that security is one of the fastest-growing research areas in computer science. Theaudience ofFASec includes thosein the formalmethods community who have(orwouldliketodevelop)adeeper interestinsecurity, andthoseinsecurity who would like to understand how formal methods can make important cont- butions to some aspects of security. The scope of FASec is deliberately broad andcoverstopics that rangefrommodelling securityrequirementsthroughsp- i?cation, analysis, and veri?cations of cryptographic protocols to certi?ed code. The discussions at FASec 2002 encompassed many aspects of security: from theoretical foundations through support tools and on to applications. Formal methods has made a substantial contribution to this exciting ?eld in the pa