A Hybrid Domain Fragile Watermarking Technique for Authentication of Color Images

Abstract

This paper presents a fragile watermarking method in which spatial, as well as frequency, domain is used for the embedding of data in color image planes. In this scheme, color images (general and medical) of size 512 × 512 are first separated into three planes. In the proposed method, two color image planes are used for embedding. The first plane, i.e., red plane is divided into four blocks, and embedding in this plane is done by using reversible watermarking based on histogram bin shifting (HBS). The second plane, i.e., the green plane is also divided into four blocks, then each block is separated into 16 × 16 blocks. Then, these blocks are further subdivided into 4 × 4 sub-blocks. Embedding in this plane is ensured by using discrete cosine transform (DCT) where coefficients are selected for embedding a fragile watermark. The third plane of an image is left unaltered. Using HBS and DCT together, the presented approach not only retrieves the data reversibly but can check the authenticity of the color images as well and, thus, validates security of the system. The presented method demonstrates an average peak signal to noise (PSNR) rate of 56.22 dB, while structural similarity index (SSIM) of 0.9985 is acquired which shows the superiority of the presented approach over previously existing colored watermarked images.