This text constitutes the refereed post-workshop proceedings of the First International Workshop on Information Security, ISW'98, held in Tatsunokuchi, Ishikawa, Japan, in September 1997. The volume presents six invited surveys together with 25 thoroughly revised full papers selected from 39 submissions. Among the topics covered are public-key cryptosystems, cryptoanalysis, digital signatures, hardware/software implementation, key management, key sharing, security management, electronic commerce, and quantum cryptology.