Differential forensics of DC-DM based watermarking

Forensics of watermarking may be desired by attackers and business competitors. It aims at not only recognizing the existence of watermark but also estimating the algorithm and its parameters. Distortion compensated-dither modulation (DC-DM) is the improved and generalized form of quantization-based embedding which is widely used in watermarking. It adopts pseudo-random dither sequences and adds back partial quantization noise so that estimation of the algorithm and its parameters seems very difficult. However, in case that changing embedding locations each time or using a private embedding domain is not a principle of designing watermarking as what we see nowadays, the differential forensics proposed in this paper, which exploits the differences between the watermarked copies, can recognize the DC-DM algorithm and estimate the algorithmic parameters well.