Extended optimization method of LSB steganalysis

Image steganalysis has attracted increasing attention recently. LSB steganalysis is one of the most active research topics. The paper proposes a method for LSB steganalysis of images, where the secret message is embedded in a given number L of the least significant bits. The proposed estimation method is an extension of Fridrich´s method from the case L = 1 to arbitrary L > 0. A weighted stego image is defined first and then estimation formula is derived. To evaluate the proposed steganalytic method, two experiments of detection and estimation are performed. It is shown that the accuracy of detecting the existence of secret messages in images and of estimating the embedding ratio of secret messages is relatively high. Estimation errors and further studies are also discussed. Experimental results and theoretical verification show that this method is an effective method of LSB steganalysis.