ASIACRYPT'98, the international conference covering all aspects of theory and application of cryptology and information security, is being held at Beijing Friendship Hotel from October 18 to 22. This is the fourth of the Asiacrypt conferences. ASIACRYPT'98 is sponsored by the State Key Laboratory of Information Security (SKLOIS), University of Science and Technology of China (USTC), and the Asiacrypt Steering Committee (ASC), in cooperation with the International Association for Cryptology Research (IACR). The 16-member Program Committee organized the scientific program and considered 118 submissions. Of these, 32 were accepted for presentation. The authors' affiliations of the 118 submissions and the 32 accepted papers range over 18 and 13 countries or regions, respectively. The submitted version of each paper was sent to all members of the Program Committee and was extensively examined by at least three committee members and/or outside experts. The review process was rigorously blinded and the anonymity of each submission are maintained until the selection was completed. We followed the traditional policy that each member of the Program Committee could be an author of at most one accepted paper. These proceedings contain the revised versions of the 32 contributed talks as well as a short note written by one invited speaker. Comments from the Program Committee were taken into account in the revisions. However, the authors (not the committee) bear full responsibility for the contents of their papers.