Topology Integrity Verification for 2D Engineering CAD Drawings

Topology information plays the most important role in engineering CAD drawings. The efficiency and quality of engineering design often depend on the topology integrity of drawings. This paper proposes a general topology authentication algorithm, which is inspired by the semi-fragile watermarking scheme, to verify the topology integrity of heterogeneous engineering CAD drawings. Topology graph is firstly built according to the topology relation among objects with uniform codes. Then, the Laplacian matrix is constructed and its Laplacian spectrum is computed to generate topology feature values. These values are then embedded into the geometric invariants of objects. Topology integrity verification is achieved through comparing the extracted binary values with the topology feature values computed according to the current topology relation. Theoretical analysis and experiments have demonstrated that the proposed scheme can not only detect and locate malicious topological modifications, but also yield strong robustness against various topology-preserving modifications, such as global and local similarity transformations, copying, mirroring and file format converting. It's believed that the proposed scheme is a general algorithm and applicable to various kinds of heterogeneous engineering CAD drawings in industry practices.