Watermarking 3D CAPD models for topology verification

The Computer-Aided Plant Design (CAPD) model characterizes its peculiar complex topology among a tremendous number of plant components under complex constraints rather than just geometrical shapes. Lots of watermarking schemes for CAD models have been proposed for geometrical information protection or authentication. However, in the literature, none of them has mentioned the problem of topology authentication for CAPD models yet. In this paper, a semi-fragile watermarking algorithm for topology authentication of CAPD models is presented. We first discuss the problem of topology authentication of CAPD models. Then a subset of the model's connection points are selected as mark points, also called watermark carriers, according to the mark point selecting principle. We encode the topological relation among components into watermarks. Afterwards, the topology based watermarks are embedded in mark points to keep them in a predefined relationship with neighboring connection points so that any changes will ruin the relationship between marked connection points and neighboring connection points. To the best of our knowledge, our algorithm is the first semi-fragile and blind scheme that can authenticate and verify the topology of CAPD models. Experimental results show that our approach not only can detect and locate malicious topology attacks such as components modification and joint ends modification, but also is robust against various non-malicious attacks such as similarity transformations and simplification.