Digital Signature Algorithm Combining with Digital Watermarking in Contourlet Domain

摘要

In order to protect copyright of digital images more effectively, paper analyzed and discussed the Contourlet coefficients'characteristics of natural image, and then an algorithm is proposed, which is a novel digital signature algorithm base on the characteristics of important coefficients in the Contourlet domain. First, do Contourlet transform to original image, and calculate the high frequency sub-bands as the indices of embedding position. Then, do Contourlet transform to the watermark image, and take the watermark image's low frequency sub-band coefficient sequence as the digital signature, then transmit the digital signature after doing RSA digital signature scheme to the data. Experimental results show that this method can prevent watermarked image form being destroyed by a variety of attacks. Additionally, using this method image data can be judged by a certificate authority center without destroys the watermarked image. This algorithm is secure and practicality.