A study on the robustness of watermark according to frequency band

Digital watermarking is one of the copyright enforcement schemes that protect copyright ownership. It is a technique which inserts imperceptible ownership information in a given digital data and identifies the owner or distributor of the digital data. In this paper, the robustness of watermark according to frequency bands is studied in many ways. First, we insert a watermark in some frequency bands of a digital image and subject the watermarked image to some image processing and attacks. Then we extract the watermark, evaluate the similarity to the original watermark and analyze the robustness of watermarking in each frequency band. In the experimental result, the embedded watermark in the high and low frequency bands is not strong enough for the special processings, including JPEG compression and other attacks. But the embedded watermark in the middle frequency band is relatively strong and excellent in the image preservation. In conclusion we find that the middle band is profitable for embedding a watermark generally.