This book presents a state-of-the-art review of current perspectives on communications and multimedia security. It examines requirements, issues, and solutions pertinent to securing information networks according to a multi-disciplinary approach covering research aspects, legal aspects, and applications. A wide spectrum of topics is discussed, including: network security (ATM, ISDN, TCP/IP); web security; protocols for entity authentication and key agreement; protocols for mobile environments; applied cryptology; watermarking; smart cards . This volume contains papers presented at the fourth Joint Working Conference on Communications and Multimedia Security (CMS'99), sponsored by the International Federation for Information Processing (IFIP) and held on September 20-21, 1999, in Leuven, Belgium. It constitutes essential reading for information security specialists, computer professionals, communication systems professionals, EDP managers and auditors, and researchers in the area.