一种基于直序扩频和跳频技术的数字水印方案

A novel watermarking scheme based on FH/DS system

打破了传统的基于直序扩频数字水印算法的局限,创新性的提出了一种结合直序扩频(DS)和跳频(FH)技术的数字水印方案.考虑到系统的频带限制,实际操作中采用软扩频方法来代替直序扩频,跳频的频率范围在图像子块离散余弦变换的中频系数中选择.通过计算相邻系数平均值来自适应调整待量化DCT系数的量化间隔,大大提升了水印系统的逼真度.根据单极性量化方法实现盲检测.整个算法使用双重密钥,使得水印系统针对JPEG压缩攻击具有较强的保密性和抗干扰性.经实验表明:水印是不可察觉的,由于水印嵌入到载体图像的DCT域,所以本算法对抵抗JPEG压缩具有很好的鲁棒性.

A novel watermarking algorithm based on FH/DS system is proposed without using the traditional method of direct sequence spread spectrum separately. Direct sequence spread spectrum technology and frequency hopping spread spectrum technology are both applied in this scheme. The frequency bandwidth of system is not so wide, so DS method is replaced by soft spread spectrum method. Intermediate frequency of the DCT coefficients are selected for using frequency hopping method. The fidelity of the watermarked image and the invisibility of the watermark had been enhanced by calculating the neighboring coefficients＇ mean value of the DCT coefficients that selected to embed the watermark. The blind extraction could be realized by utilizing unipolar quantification method. Duo Keys are applied in this scheme so that the confidentiality and anti-interference property are enhanced greatly. Experimental results show that the watermark proposed in this paper is invisible. This scheme is robust against JPEG compress because DCT domain is selected to embed the watermark.