Cryptanalysis of 'Wavelet Tree Quantization' Watermarking Scheme

摘要

Here we study a recently proposed watermarking scheme based on "Wavelet Tree Quantization" (WTQ) which has been presented by Wang and Lin in IEEE Transactions on Image Processing, February 2004. In the scheme, the wavelet coefficients corresponding to same spatial locations are grouped together. Two such groups, selected at random, are merged to form a super tree. Some of these super trees are quantized to embed the watermark signal in the image. In the process of cryptanal-ysis we can identify the groups which are quantized during watermark insertion process. We then select the non-quantized groups and quantize them to remove the watermark. Experimental results show that the watermark is completely removed by this attack. The cryptanalysis falls under cipher text only jamming attack which requires a single watermarked copy.