This book constitutes the refereed proceedings of the 11th Australasian Conference on Information Security and Privacy, ACISP 2006, held in Melbourne, Australia, July 2006. The book presents 35 revised full papers and 1 invited paper, organized in topical sections on stream ciphers, symmetric key ciphers, network security, cryptographic applications, secure implementation, signatures, theory, security applications, provable security, protocols, as well as hashing and message authentication.