Analysis of optimal search ing interval for estimation of amplitude modifications in quantization-based audio watermark detection

Quantization-based watermarking schemes such as SCS and QIM are known to be very vulnerable to the amplitude modification attack. Thus accurate estimation of the amplitude modification, i.e., estimation of a modified quantization step size is required before watermark detection. In this paper, we propose a robust algorithm to estimate the modified quantization step size with an optimal search interval. The optimal search interval that considers both detection performance and computational complexity is derived analytically. Experimental results for real audio data show that the derived optimal search interval provides the accurate estimation of the modified quantization step size under amplitude modification attack.