8. Managing CAD Data as a Multimedia Data Type Using Digital Watermarking

Three-dimensional (3D) model, including 3D geometric CAD model, has come to be recognized as a “multimedia” data type, along with such data types as sound, text, still image, and movie. As a data type, each one of these data types has a set of operations associated with it. Representative of operations are input, output, editing, indexing, hyper-linking, compression, similarity-based search, and some form of security, such as authentication, tamper detection, and intellectual property (IP) management. This paper discusses digital watermarking technology for 3D geometric CAD data, which may offer a solution to such security related issues of authentication, tamper detection, and intellectual property management. This paper first examines 3D CAD data as a multimedia data type, followed by discussion on its watermarking opportunities. The paper then presents multiple approaches to watermark mechanical CAD models defined by using parametric curves and surfaces. In particular, two methods that targets NURBS curves and surfaces are presented. The methods, one based on reparameterization and the other based on knot insertion, preserves exact geometric shape of target NURBS objects.