This book constitutes the refereed conference proceedings of the 18th Australasian Conference on Information Security and Privacy, ACISP 2013, held in Brisbane, Australia, in July 2013. The 28 revised full papers presented were carefully selected from 78 submissions. Conference papers are organized in technical sessions, covering topics of Cryptoanalysis, RSA, Lattices and Security Proofs, Public Key Cryptography, Hashing, Signatures, Passwords, Mobile Security, and Secret Sharing.