Information and Communications Security : 6th International Conference ICICS 2004 Malaga Spain October 27 29 2004. Proceedings This book constitutes the refereed proceedings of the 6th International Conference on Information and Communications Security ICICS 2004 held in Malaga Spain in October 2004. The 42 revised full papers presented were carefully reviewed and selected from 245 submissions. The papers address a broad range of topics in information and communication security including digital signatures group signature schemes e commerce digital payment systems cryptographic attacks mobile networking authentication channel analysis power analysis attacks mobile agent security broadcast encryption AES security analysis XTR access control and intrusion detection