This book constitutes the refereed proceedings of the First International Workshop on Practice and Theory in Public Key Cryptography, PKC'98, held in Pacifico Yokohama, Japan, in February 1998. The volume presents four invited contributions together with 18 revised full papers selected from 30 submissions. The papers address all current issues in research and design in the area including digital signature schemes, digital payment systems, electronic commerce, cryptographic protocols, as well as foundational issues like integer factorization, elliptic curve aspects, hash functions, finite fields, etc.