Huge amounts of digital visual data are stored on different media and exchanged over various sorts of networks nowadays. Often, these visual data contain private or confidential informations or are associated with financial interests. As a consequence, techniques are required to provide security functionalities like privacy, integrity, or authentication especially suited for these data types. A relatively new field, denoted Multimedia Security , is aimed towards these emerging technologies and applications.

Several dedicated international meetings have emerged as a forum to present and discuss recent developments in this field, among them Security, Steganography, and Watermarking of Multimedia Contents (organised in the framework of SPIE s annual Electronic Imaging Symposium in San Jose) as the most important one. Further important meetings are Communications and Multimedia Security (CMS) (annually organised in the framework of IFIP s TC6 and TC11) and the ACM Multimedia Security Workshop . Additionally, a significant amount of scientific journal special issues has been devoted recently to topics in multimedia security (e.g. ACM/Springer Multimedia Systems, IEEE Transactions on Signal Processing supplement on Secure Media, Signal Processing, EURASIP Applied Signal Processing, ). The first comprehensive textbook covering this field, the Multimedia Security Handbook [54] is published in autumn 2004.

Besides watermarking, steganography, and techniques for assessing data integrity and authenticity, providing confidentiality and privacy for visual data is among the most important topics in the area of multimedia security, applications range from digital rights management (DVD, DVB and pay-TV) to secured personal communications (e.g., encrypted video conferencing). In the following we give some...