This volume is a collection of refereed papers presented during AUSCRYPT '90 held in Sydney, Australia, January 8-11, 1990. This was the first conference of a series sponsored by the International Association for Cryptological Research (IACR) in addition to the EUROCRYPT series held in European countries and the CRYPTO series held in Santa Barbara, California. The volume is divided into sections on: - Public-key cryptosystems - Pseudorandomness and sequences - Network security - Authentication - Block ciphers - Zero-knowledge prools - Theory - Applications - Implementations. It is a "must" for all researchers and students interested in recent progress in cryptology.