Defending against statistical steganalysis

Abstract

The main purpose of steganography is to hide the occurence of communication. While most methods in use today are invisible to the observer's senses, mathematical analysis may reveal statistical discrepancies in the stego medium. These discrepancies expose the fact that hidden communication is happening. This paper presents a new method to preserve the statistical properties of the cover medium. After applying a correcting transform to an image, statistical steganalysis is no longer able to detect the presence of steganography. We present an a priori estimate to determine the amount of data that can be hidden in the image while still being able to maintain frequency count based statistics. This way, we can quickly choose an image in which a given message can be hidden safely. To evaluate the eectiveness of our approach, we present statistical tests for the JPEG image format and explain how our new method defeats them. Februrary 12, 2001 Center for Information Technology Inte...