To facilitate the embedding of fingerprinting payload corresponding to multiple re-sellings of a single image, multiple re-watermarking is a convenient technique. In this application context, oblivious detection techniques are important. Quantisation-based embedding technique are difficult to apply in this context without adapting them to the multiple watermarking scenario. We investigate two extensions to a wavelet coefficient-tree based embedding technique which turn out to improve detection performance in case of multiple re-watermarking.

This letter describes an attack on the recently proposed ldquowatermarking method based on significant difference of wavelet coefficient quantizationrdquo by Lin While the method is shown to be robust against many signal processing operations, security of the watermarking scheme under intentional attack exploiting knowledge of the implementation has been neglected. We demonstrate a straightforward attack which retains the fidelity of the image. The method is therefore not suitable for copyright protection applications. Further, we propose a countermeasure which mitigates the shortcoming.