A Robust Image Authentication Method Based on Wavelet Transform and Teager Energy Operator

A novel digital watermarking for image authentication is proposed in this paper. Most previous proposed watermarking algorithms embed sequences of random numbers as watermarks. Here images are taken as watermarks for embedding. In the proposed approach, the host image is decomposed into wavelet coefficients. Local entropies of wavelet coefficients in the low-frequency subband are calculated by a Teager energy operator to select embedding locations. The selected coefficients are quantized and the watermark is encrypted; then the least significant bits or the second least significant bits of the quantized coefficients are replaced by the encrypted watermark. At last, the watermarked image is synthesized from the changed and unchanged wavelet coefficients. The experiments show that the proposed approach provides extra robustness against JPEG compression compared to the traditional embedding methods. Moreover, the proposed approach has no need of the original image to extract watermarks and need not sort the embedded coefficients and the watermark.