This book constitutes the refereed proceedings of the 9th International Conference on Information Security, ISC 2006, held on Samos Island, Greece in August/September 2006.

The 38 revised full papers presented were carefully reviewed and selected from 188 submissions. The papers are organized in topical sections on software security, privacy and anonymity, block ciphers and hash functions, digital signatures, stream ciphers, encryption, pervasive computing, network security, watermarking and digital rights management, intrusion detection and worms, key exchange, security protocols and formal methods, and information systems security.