A selective authentication watermarking algorithm for 2D CAD engineering drawings based on entity localization

This paper presents a selective authentication watermarking algorithm for 2D CAD engineering drawings based on entity localization. Firstly, get the vertexes of each entity and map them to log-polar coordinates, the sum of amplitude before accuracy and handle of previous entity is used to generate a watermark. Then use the improved difference expansion (IDE) algorithm to embed the watermark into corresponding amplitude. Theoretical analysis and experimental results show that the proposed algorithm is not only robust against global geometric operations such as translation, rotation and scaling, but extremely sensitive to malicious attacks which affect the normal use of drawings, meanwhile it can also locate tampering to a specific entity. It provides an effective method for integrity authentication of engineering drawings.