Abstract: Since it’s difficult to authenticate the topological relation in the 2-dimensional engineering
CAD drawing, a topological integrity authentication algorithm is proposed based on Hashing in this
paper. Firstly, the algorithm extracts the topological relations of the drawings to generate the topology
graph. Secondly, the components in the engineering CAD drawing are encoded, and the local
topological quantization pattern (LTQP) is proposed to quantize the topological features of each
component. Then, the components are divided into five categories according to their coding, and a
Hash sequence is generated by discrete cosine transform based on the LTQP values. Finally, the Hash
sequence of each category is combined to obtain the complete Hash sequence of the drawing. The
experimental results show that the algorithmis robust to rotation, scaling and translation in
engineering CAD drawings, and is vulnerable to the change of topological connection. By classifying
the components to generate a Hash sequence, the algorithm can locate the type of components which
is subjected to the topology attack.

Key words: engineering CAD drawing, topology authentication, local topological quantization pattern;
discrete cosine transform, Hashing