pearson correlation coefficient

In this paper, we described Pearson's correlation coefficient inefficiency for analyzing the relationship between an image and encrypted one. Also, the information index was investigated as a suitable substitute for Pearson correlation coefficient. This weakness is independent of the encryption system of the image encryption; however, two encryption algorithms such as modified AES and W7 stream cipher have been used for laboratory calculations. In addition, by quantitative and qualitative examination of other standards for encryption analyzing of the image, the information index, in comparison with the Pearson correlation coefficient, shows the strengths and weaknesses of the image encryption algorithms better.