Some years ago, businesses could choose whether to migrate to electronic commerce, however, today it seems they have no choice. Predictions indicate that companies that do not make the necessary changes will be overrun by competition and ultimately fail. Therefore, we see more and more companies undergoing tremendous transformationin order to adapt to the new business paradigm. At the same time new companies are being established. One thing these companies have in common is the increased dependency on security technology. The invention of electronic commerce has changed the role of - curity technologies from being merely a protector to being also an enabler of electronic commerce, and it is clear that the development of security techn- ogy is a key enabler in the growth and deployment of electronic commerce. This has been recognised at European level (European Union 1997e). The launch of a comprehensive EU policy in the area of security in open networksisfairlyrecentwiththeadoptionofaCommunicationoncryptog- phy inOctober 1997(EuropeanUnion1997c). A veryimportantcomplement and support to the European policy is the European Commission's contri- tion to overcometechnological barriers by giving special importance to R&D (Research and Development) activities. The SEMPER project was launched in September 1995 and was funded partly by the European Community within the Advanced Communication Technologies and Services (ACTS) speci?c research programme part of the Fourth Framework Program (1994-1998). In this book the SEMPER project team presents in a coherent, integrated, and readable form the issues - dressed, themotivationfortheworkcarriedout, andthekeyresultsobtained. SEMPER is an innovative project in several aspects.