数字水印中的随机共振现象

Stochastic resonance in digital watermarking

首先介绍了一个可以用于检测通信系统中基带二进制脉冲幅度调制(PAM)信号的非周期随机共振信号处理器.在此基础上实现了一个基于该信号处理器的DCT域数字图像水印算法.在该算法中,水印和选取的图像DCT交流系数分别看作随机共振信号处理器的输入信号和噪声,他们与双稳非线性系统共同组成一个随机共振系统.进行了仿真实验,结果表明系统不仅在未受到攻击的情况下会出现随机共振现象,而且在受到攻击的情况下也会出现随机共振现象,甚至出现在受到攻击情况下的误比特率比没有受到攻击情况下的误比特率低的现象,这在传统的数字水印系统中是很难解释的,但这是基于非线性的随机共振信号处理本身所具有的属性.

A signal processor based on an aperiodic stochastic resonance （ASR） is introduced. The processor can detect the base-band binary pulse amplitude modulation （PAM） signal. Then a digital image watermarking algorithm in the discrete cosine transform （DCT） domain based on the processor is implemented. In this algorithm, the watermark and the DCT alternating current （AC） coefficients of the image are viewed as the input signal and the channel noise of the processor input, respectively. Numerical simulations are carried out and the results show that the SR effect occurs not only when the system is not attacked, but also when the system suffers from some kinds of attacks. In conventional watermarking systems, it is difficult to explain why the detection bit error ratio （BER） of a watermarking system suffering from some kinds of attacks is lower than that of the system without attack. In the new watermarking algorithm, it is shown that the DCT AC coefficients of the image as well as the noise imported by the attacks will cooperate within the bi-stable system to improve the nerformance cf the watermark detection.