This book constitutes the refereed proceedings of the Third International Workshop on Practice and Theory in Public Key Cryptography, PKC 2000, held in Melbourne, Victoria, Australia in January 2000. The 31 revised full papers presented were carefully reviewed and selected from 70 submissions. Among the topics addressed are cryptographic protocols, digital signature schemes, elliptic curve cryptography, discrete logarithm, authentication, encryption protocols, key recovery, time stamping, shared cryptography, certification, zero-knowledge proofs, auction protocols, mobile communications security, etc.