A novel image scrambling degree blind evaluation scheme based on Bhattacharyya coefficient

Image scrambling degree evaluation is important in assessing the security of image scrambling schemes. In this paper, a novel image scrambling degree (ISD) evaluation scheme based on Bhattacharyya coefficient is proposed. The image for evaluation is divided into non-overlapped blocks with the size 16×16 and then the Bhattacharyya coefficients of each block and the entire image is calculated, among which the minimum one is finally selected to measure the ISD. This scheme is simple in principle and convenient for use in practical applications, due to the non-engagement of original image and low computation complexity. Experimental results show that the proposed method is correct and effective in evaluating the SD of image under different types of image scrambling, including pixel positions permutation, pixel values shuffling.