Annotation of cultural heritage 3-D models by robust data embedding in the object mesh

This paper presents a novel method of the low-level data hiding for the cultural heritage watermarking and authentication. Method involves the algorithm for robust and blind embedding the data bits into a geometrical structure of three-dimensional (3D) mesh models and the data protection algorithm. In the first step the vector of the stabile vertex is selected using powerful vertex extraction algorithm, which calculates the most relevant geometrical and topological features of the 3D mesh model. Watermark and/or authentication data is subjected to an error-correction encoding in the second step of the algorithm. The runlength encoding converts protected bits to a run of bits to ensure synchronization and thus converts a deletion channel with infinite memory to a memoryless channel. Finally, data bits are embedded into structure of the cultural heritage model by changing the spatial Euclidean positions of mesh primitives. Choosing the one of two quantizers of the Quantization Index Modulation (QIM) algorithm determines a value of the embedded data bit. Watermark and/or authentication data is extracted from a stego object in the reverse process using the stego key only. Due to the retrieving phase of algorithm does not need information about original model a blindness of the whole process is ensured.