Tamper Proofing 3D Motion Data Streams

This paper presents a fragile watermarking technique to tamper proof (Mocap) motion capture data. The technique visualizes 3D Mocap data as a series of cluster of points. Watermarks are embedded using clusters points, where a bit is encoded in each cluster. The four point encoding mechanism uses a combination of one point encoding and three point encoding schemes. Using these schemes it is possible to distinguish between affine transformations, noise addition and reverse ordering attacks. The bits are encoded and decoded in this scheme using an extension of quantization index modulation. It has been shown that distortions are reduced to achieve imperceptibility of the watermark. The bit encoding schemes give the flexibility to achieve better accuracy in tamper detection. In addition, the paper suggests a probabilistic model, which is a function of the watermark size. Using this model, it has been proved that larger watermark sizes achieve higher accuracy in tamper detection.