Copyright protection of architectural CAD drawing using the multiple watermarking scheme

The paper proposes a digital watermarking technique for CAD vertex-based architectural drawings using lines, arcs, and circles to prevent unlawful reproduction and distribution. After extracting lines, arcs, and circles from the drawing, the watermarks are embedded using an adaptive algorithm related to the length of the line, angle of the arc, and radius of the circle. The proposed watermarking scheme is robust to various attacks, like a geometrical transformation. Also, the proposed method satisfies transparency, as the embedding strength is suited to each component. Experimental results confirmed the robustness and invisibility of the embedded watermarks in several architectural drawing conversions