A study on a watermarking method for both copyright protection and tamper detection

Most of watermarking methods are either robust watermarking for copyright protection or fragile watermarking for tamper detection. We propose a watermarking method that has both robustness against image processing and ability of tamper detection. In the proposed method, three wavelet coefficients are treated as a vector and one bit of a watermark is embedded by using order relationships among the coefficients. The number of order relationships among three coefficients is six, while only two patterns of relationships are needed to represent one bit of a watermark. Order relationships that are not assigned to a watermark bit can be used for tamper detection.