Robust hybrid watermarking approach for 3D multiresolution meshes based on spherical harmonics and wavelet transform

Since the 3D mesh security problems imposed themselves, attempts to design watermarking algorithms targeting this data type have continued to grow up to secure data shared by remote users. The originality of the present approach is to insert a whole grayscale image in hybrid domain by using wavelet transform and spherical harmonics. Our algorithm includes then two rounds of insertion. The first is operating multiresolution domain by applying wavelet transform. The watermark, which is an image already coded using a convolutional encoder, is embedded into wavelet coefficients (using Least Significant Bit method) after a transformation to spherical coordinate system and a modulation step. Finally watermarked mesh is reconstructed using inverse wavelet transform. This mesh undergoes a second round on watermarking using spherical harmonics. In this case the same steps are executed to embed data into SHs harmonic coefficients before reconstructing the final version of the watermarked mesh. The experimentation of our approach has shown a very high insertion rate due to the use of hybrid insertion domain, while maintaining the mesh quality. Watermarked mesh and extracted data are obtained in real time. Our approach is also robust against the most popular attacks. Our results show that the present approach improves the existing works.