Mixing chaotic watermarks for embedding in wavelet transform domain

A multiresolution watermarking scheme, in which mixed chaotic sequences are embedded in the wavelet transform domain, is proposed. This algorithm takes advantage of the multiresolution feature of the wavelet transform and the non-relevant feature of chaotic signals. Chaotic binary sequences generated by Chebyshev maps are discussed. The chaotic mixing watermarks are added to some important coefficients located in the high-pass subbands. A group of adaptive thresholds based on each subband is selected and watermarks are embedded by modifying the coefficients whose amplitude is larger than these thresholds. The watermarked image is obtained by using the reverse wavelet transform. The experimental results demonstrate that the watermarks generated by the proposed algorithm are invisible and robust against commonly used image processing techniques. Choosing a chaotic map and the method of obtaining the binary sequences are the key to protecting the security of the sequences