An international community of researchers is now flourishing in the area of cryptology-there was none half-a-dozen years ago. The intrinsic fascination of the field certainly is part of the explanation. Another factor may be that many sense the importance and potential consequences of this work, as we move into the information age. I believe that the various meetings devoted to cryptology over the past few years have contributed quite significantly to the formation of this community, by allowing those in the field to get to know each other and by providing for rapid exchange of ideas. CRYPTO 83 was once again truly the cryptologic event of the year. Many of the most active participants continue to attend each year, and attendance continues to grow at a healthy rate. The informal and collegial atmosphere and the beach side setting which contribute to the popularity of the event were again supported by flawless weather. The absence of parallel sessions seemed to provide a welcome opportunity to keep abreast of developments in the various areas of activity. Each session of the meeting organized by the program committee is repre sented by a section in the present volume. The papers were accepted by the program committee based on abstracts, and appear here without having been otherwise refereed. The last section contains papers presented at the informal rump session. A keyword index and an author index to the papers is provided at the end of the volume.