A novel pre-warping technique for 3D meshes is presented to prevent collusion attacks on fingerprinted 3D models. By extending a similar technique originally proposed for still images, the surface of watermarked 3D meshes is randomly and imperceptibly pre-distorted to protect embedded fingerprints against collusion attacks. The peculiar problems set by the 3D nature of the data are investigated and solved by preserving the perceptual quality of warped meshes. The proposed approach is

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... of the chosen fingerprinting system. The proposed algorithm can be implemented inside a watermarking chain, as an independent block, before performing features extraction and watermark embedding. It follows that the detection algorithm is not influenced by the anti-collusion block. The application of different collusion strategies has revealed the difficulty for colluders to inhibit watermark detection while ensuring an acceptable quality of the attacked model. Keywords: 3D watermarking, collusion attack, pre-warping * One may wonder whether the hacker could scramble the vertex order so to imped correct watermark detection. The effectiveness of such an attack, of course, depends on the watermarking scheme in use. Here, we only consider watermarking schemes 67 that are unaffected by vertices scrambling.