Semi-fragile self-recoverable watermarking algorithm based on wavelet group quantization and double authentication

Semi-fragile self-recoverable watermarking algorithms are important to meet various requirements such as security, robustness, localization, and image recovery. However, current approaches are not adequate for this importance. Thus, we propose a novel semi-fragile and self-recoverable watermarking algorithm based on a group quantization and double authentication method. In the proposed algorithm, a target image is first split into 16 x16 image blocks. For each image block, a five-bit authentication watermark is generated from the first-order statistical moment of the block and then is embedded into the mid-frequency band of another image block by a novel group-based wavelet quantization method. With the generated watermarks, image security is enhanced by randomly permuting coefficients among a group and image robustness is improved by embedding the watermark in the largest coefficient inside a sub-group by significant difference parity quantization. The proposed double authentication ring structure effectively improves the image localization accuracy. Recovered image is a better approximate to the original image. Experimental comparisons of ours with other algorithms shows the effectiveness of the proposed self-recoverable and semi-fragile watermarking algorithm.