This book presents a state-of-the art review of current perspectives on Communications and Multimedia Security. It contains the Proceedings of the 3rd Joint Working Conference of IFIP TC6 and TC11, arranged by the International Federation for Information Processing and held in Athens, Greece in September 1997. The book aims to cover the subject of Communications and Multimedia Systems Security, as fully as possible. It constitutes an essential reading for information technology security specialists; computer professionals; communication systems professionals; EDP managers; EDP auditors; managers, researchers and students working on the subject.