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TECHNICAL RESEARCH REPORT Anti-Collusion Fingerprinting for Multimedia by Wade Trappe, Min Wu, K.J. Ray Liu TR 2002-17 I R INSTITUTE FOR SYSTEMS RESEARCH ISR develops, applies and teaches advanced methodologies of design and analysis to solve complex, hierarchical, heterogeneous and dynamic problems of engineering technology and systems for industry and government. ISR is a permanent institute of the University of Maryland, within the Glenn L. Martin Institute of Technology/A. James Clark School of Engineering. It is a National Science Foundation Engineering Research Center. Web site http://www.isr.umd.edu Anti-Collusion Fingerprinting for Multimedia Wade Trappe, Min Wu, Zhen Wang, and K. J. Ray Liu Department of Electrical and Computer Engineering University of Maryland, College Park, MD 20742 E-mail: wxt, minwu, zhenwang, kjrliu @eng.umd.edu Abstract Digital fingerprinting is a technique for identifying users who might try to use multimedia content for unintended purposes, such as redistribution. These fingerprints are typically embedded into the content using watermarking techniques that are designed to be robust to a variety of attacks. A cost-effective attack against such digital fingerprints is collusion, where several differently marked copies of the same content are combined to disrupt the underlying fingerprints. In this paper, we investigate the problem of designing fingerprints that can withstand collusion and allow for the identification of colluders. We begin by introducing the collusion problem for additive embedding. We then study the effect that averaging collusion has upon orthogonal modulation. We introduce an efficient detection algorithm for identifying the fingerprints associated with K colluders that requires O(K log(n/K)) correlations for a group of n users. We next develop a fingerprinting scheme based upon code modulation that does