A local Wiener attack for additive watermarks

A method for attacking an additive watermark is proposed. A watermark pattern is estimated by applying a local Wiener filter to each frequency band of the stego signal. The method exploits local differences in power spectrum density (psd) between the watermark and the host signals. Experiments have shown that the attack is more than 10 times effective compared to the existing global Wiener attack in most cases. The signal power of the estimate by the attack can be used as a measure of the watermark secureness. Modulating the watermark strength adaptively according to the host signal´s local contents generally makes the watermark more difficult to estimate.