Wavelet tree based watermarking algorithms are generally using the energy difference among grouped wavelet coefficients for invisible watermark embedding and extraction. According to cryptanalysis of wavelet tree quantization (WTQ) scheme, the robustness of watermarking is weak if the wavelet tree group coefficients are only unilaterally modulated. Therefore, bilaterally modulated techniques like modified wavelet tree quantization (MWTQ) and wavelet tree group modulation (WTGM) improve the security since the attackers can not decipher how tree coefficients are modulated. However, MWTQ needs the wavelet tree group information as the extra information which results the method is not purely blind for watermark extraction. For that matter, a novel wavelet tree group based watermarking using energy modulation and consistency check (WW-EMCC) is proposed in this study which not only resists the cryptanalysis attacks but also provides the dual function of choices for blind (WW-EMCCB) and non-blind (WW-EMCCN) watermark embedding. The essence of WW-EMCC design is to embed the watermark in the tree group coefficients as well as the relationship between the tree groups. Such approach extends the bilateral modulation into higher dimension of modulation and increase the robustness of security. In addition, WW-EMCC can even be modified as a captioning watermarking with lossless image quality which integrates watermarking and cryptography for copyright protection. This study has performed intensive comparison for the proposed scheme with WTQ, MWTQ and WTGM under various geometric and nongeometric attacks. The experimental results demonstrate that the proposed technique yields better performance with higher degree of robustness.
- Wavelet Transform
- Wavelet tree quantization