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Robust Mesh Watermarking

Report ID:
December 1998
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Watermarking provides a mechanism for copyright protection of digital
media by embedding information identifying the owner in the data. The
bulk of the research on digital watermarks has focused on media such as
images, video, audio, and text.

Robust watermarks must be able to survive a variety of "attacks",
including resizing, cropping, and filtering. For resilience to such
attacks, recent watermarking schemes employ a "spread-spectrum" approach -
they transform the document to the frequency domain (e.g. using DCT) and
perturb the coefficients of the perceptually most significant basis
functions. In this paper we extend this spread-spectrum approach for the
robust watermarking of arbitrary triangle meshes.

Generalization of the spread spectrum techniques to surfaces presents two
major challenges. First, arbitrary surfaces lack a natural
parametrization for frequency-based decomposition. Our solution is to
construct a set of scalar basis function over the mesh vertices using a
multiresolution analysis of the mesh. The watermark is embedded in the
mesh by perturbing vertices along the direction of the surface normal,
weighted by the basis functions. The second challenge is that attacks
such as simplification may modify the connectivity of the mesh. We use an
optimization technique to resample an attacked mesh using the original
mesh connectivity. Results demonstrate that our watermarks are resistant
to common mesh processing operations such as translation, rotation,
scaling, cropping, smoothing, simplification, and resampling, as well as
malicious attacks such as the insertion of noise, modification of
low-order bits, or even insertion of other watermarks.

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