The Proceedings contain twenty selected, refereed contributionsarising from the International Conference on Public-Key Cryptographyand Computational Number Theory held in Warsaw, Poland, on September11-15, 2000.The conference, attended by eightyfive mathematicians from elevencountries, was organized by the Stefan Banach InternationalMathematical Center.This volume contains articles from leading experts in the world oncryptography and computational number theory, providing an account ofthe state of research in a wide variety of topics related to theconference theme. It is dedicated to the memory of the Polishmathematicians Marian Rejewski (1905-1980), Jerzy Róøycki (1909-1942)and Henryk Zygalski (1907-1978), who deciphered the military version ofthe famous Enigma in December 1932 – January 1933. A noteworthyfeature of the volume is a foreword written by Andrew Odlyzko on theprogress in cryptography from Enigma time until now.