Strong robust zero watermarking algorithm based on NSCT transform and image normalization

In order to improve the robustness of the watermark, a strong robust zero watermarking algorithm based on NSCT transform and image normalization is proposed. In the proposed scheme, the cover image is mapped to the geometric invariant space by using the image normalization technique based on invariant moment. Then, the effective part of the normalized image is extracted by using the square of the unit circle and carried on NSCT transform. The low frequency coefficient sub band is decomposed by block singular value, and zero watermarking is generated according to the odd of the highest digit of the maximum singular value of each block. Experimental results show that the algorithm can not only effectively resist noise, filtering, JPEG compression, rotation, scaling, long and wide transformation and other attacks, but also has good imperceptibility and robustness.

I. Introduction

Robustness is an important index to evaluate the performance of watermarking algorithm. How to ensure robustness under good and insensible conditions is a research hotspot in current. Traditional watermarking algorithm needs to modify the original carrier when embedding the watermark. This reduces the imperceptibility of the carrier. In order to solve this problem, Wen et al. [1] proposed the concept of zero watermarking. In the proposed scheme, the characteristic of carrier is used to construct the watermarking. Because the original carrier is not modified, the contradiction between the imperceptibility and the robustness is solved.