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 The Program Committee received 155 submissions and selected 33 papers for presentation; one of them was withdrawn by the authors.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.