EUROCRYPT 2001, the 20th annual Eurocrypt conference, was sponsored by the IACR, the International Association for Cryptologic Research, see http://www. iacr. org/, this year in cooperation with the Austrian Computer - ciety (OCG). The General Chair, Reinhard Posch, was responsible for local or- nization, and registration was handled by the IACR Secretariat at the University of California, Santa Barbara. In addition to the papers contained in these proceedings, we were pleased that the conference program also included a presentation by the 2001 IACR d- tinguished lecturer, Andrew Odlyzko, on "Economics and Cryptography" and an invited talk by Silvio Micali, "Zero Knowledge Has Come of Age. " Furthermore, there was the rump session for presentations of recent results and other (p- sibly satirical) topics of interest to the crypto community, which Jean-Jacques Quisquater kindly agreed to run. The Program Committee received 155 submissions and selected 33 papers for presentation; one of them was withdrawn by the authors. The review process was therefore a delicate and challenging task for the committee members, and I wish to thank them for all the e?ort they spent on it. Each committee member was responsible for the review of at least 20 submissions, so each paper was carefully evaluated by at least three reviewers, and submissions with a program committee member as a (co-)author by at least six.

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."

This book, based on the author's Ph.D. thesis, was selected during the 1995 GI Doctoral Dissertation Competition as the winning thesis in the foundations-of-informatics track.
Securing integrity for digital communications in the age of global electronic information exchange and electronic commerce is vital to democratic societies and a central technical challenge for cryptologists. As core contribution to advancing the state of the art, the author develops the new class of digital fail-stop signatures. This monograph is self-contained regarding the historical background and cryptographic primitives used. For the first time, a general and sophisticated framework is introduced in which innovative fail-stop signatures are systematically presented and evaluated, from theoretical foundations to engineering aspects.