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Guest Editors' Introduction: Image Security

Christoph Busch, Fraunhofer Institute of Computer Graphics
Klara Nahrstedt, University of Illinois at Urbana-Champaign
Ioannis Pitas, University of Thessaloniki

Pages: pp. 16-17

Over the past decades, research in security has concentrated on the development of algorithms and protocols for encryption, authentication, and integrity of textual data or data with similar characteristics. Despite tremendous advances in security—specifically, the development of asymmetric cryptographic protocols and the inception of strong symmetric ciphers—plenty of security problems still afflict systems. For example, hackers exploiting weaknesses in other systems and the use of inadequate (too short) cipher keys produce frequent news headlines about broken security systems.

Despite the news headlines, such problems have been well explored and even solved in principle, therefore they aren't the primary focus of this special theme issue. Rather, the articles here cover the unsolved problems in image security, which relate fairly closely to computer graphics. The unsolved challenges arise from the increased availability and distribution of multimedia content over Internet services such as the World Wide Web and their implications for intellectual property protection and copyright issues.

A growing number of scientific groups in computer science and cryptography have confronted these challenges. Researchers are currently working on issues such as visual cryptography, mechanisms for the integrity of image material, digital signatures for multimedia data, and data hiding techniques. Data hiding, which has achieved the highest popularity, contemplates the crucial needs for protecting intellectual property rights on multimedia content like images, video, audio, and others. These needs demand robust solutions due to the explosion of publicly available multimedia information and the easiness with which this information can be distributed, copied, and modified. Watermarking technology meets these demands and provides a feasible approach to protect against—and prove—illegal copying and redistribution in the digital world.

This special theme issue presents four articles that discuss watermarking solutions for dedicated media types such as images, video, and geometric models. They range from an overview of fundamental watermarking concepts to the latest research results.

In "A Watermarking Framework for Copyright Protection of Digital images," George Voyatzis and Ioannia Pitas review fundamental watermarking concepts and develop a generic model for protecting the copyrights of digital products including a trusted registration authority.

"Digital Watermarking: From Concepts to Real-Time Video Applications" by Christoph Busch, Wolfgang Funk, and Stephen Wolthusen focuses on the specific demands and real-time requirements for video protection. Their solution, which is robust against strong MPEG-2 compression, is very important to the broadcasting and video stock industries.

Boon-Lock Yeo and Minerva Yeung address a new area of watermarking via 3D polygonal models with "Watermarking of 3D Objects for Verification." Their article takes an essential step into this untouched area. They provide mechanisms for embedding watermarks into geometric models as well as detection mechanisms for unauthorized modifications.

"Geometry-Based Watermarking of 3D Models" by Oliver Benedens presents fundamental progress in the same field. His contribution formulates a new definition for robustness of watermarks in correlation to 3D models, proposes a watermarking mechanism, and evaluates its robustness against a polygon simplification.

Finally, we would like to mention that we could not consider all the outstanding submissions received for this theme issue because of page limitations. Contributions were reviewed by up to six security experts from all over the world. We would like to thank all the reviewers, who provided constructive comments and strongly influenced the selection. Their choices allow us to provide a high-quality overview of the state-of-the-art in the field and describe exciting new developments and technologies. We hope you will enjoy reading the following pages. $\qquad\SSQBX$

About the Authors

Christoph Busch is head of the Department of Security Technology for Graphics and Communication Systems at the Fraunhofer Institute for Computer Graphics, where he is responsible for the acquisition, management, and control of various applied research and development projects. He is also a lecturer on applied wavelet transforms in the educational program of the Computer Graphics Center. He has participated in a series of projects with the Deutsche Telekom AG and Mitsubishi Corp., and is currently a partner in several European projects, including ACTS's Talisman and Octalis projects and Esprit's Aimedia and Filigrane project, all of which deal with copyright protection and conditional access for interactive multimedia services.
Busch studied geodetic sciences at the Technical University of Darmstadt, where he received a PhD in computer graphics in 1997.
Klara Nahrstedt is an assistant professor in the Computer Science Department at the University of Illinois at Urbana-Champaign. Her research interests are in quality-of-service (QoS) aware resource management for distributed multimedia systems and multimedia security. She received a BA in mathematics from Humboldt University, Berlin in 1984 and an MS in numerical analysis from the same university in 1985. In 1995 she received a PhD from the University of Pennsylvania in the department of Computer and Information Science.
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Ioannis Pitas is a professor at the Department of Informatics at the University of Thessaloniki. His current research interests are in the areas of digital image processing, multidimensional signal processing, and computer vision. He received the dipolma of electrical engineering in 1980 and a PhD in electrical engineering in 1985 at the University of Thessaloniki, Greece. He co-authored the book Nonlinear Digital Filters: Principles and Applications (Kluwer, 1990) and authored Digital Image Processing Algorithms (Prentice Hall, 1993). He is currently an associate editor of IEEE Transactions on Neural Networks.
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