12 March 2001
Steganalysis of Images Created Using Current Steganography Software
Neil F. Johnson and Sushil
Center for Secure Information Systems
George Mason University Fairfax, Virginia 22030-4444
"This article appears in the Lecture Notes in Computer Science, Vol. 1525, published by Springer-Verlag (1998) on pages 273-289 and is part of the proceedings for the Second Information Hiding Workshop held in Portland, Oregon, USA, April 15-17, 1998."
Steganography is the art of passing information in a manner that the very existence of the message is unknown. The goal of steganography is to avoid drawing suspicion to the transmission of a hidden message. If suspicion is raised, then this goal is defeated. Steganalysis is the art of discovering and rendering useless such covert messages. In this paper, we identify characteristics in current steganography software that direct the steganalyst to the existence of a hidden message and introduce the ground work of a tool for automatically detecting the existence of hidden messages in images.
Detecting Hidden Information
Looking for signatures
Examples of Palette Signature: S-Tools, SysCop, Mandelsteg, Hide and Seek, Hide4PGP, Jsteg-Jpeg
Destroying Steganography and Watermarks
"Steganography transmits secrets through apparently innocuous covers in an effort to conceal the existence of a secret. Digital image steganography and its derivatives are growing in use and application. In areas where cryptography and strong encryption are being outlawed, citizens are looking at steganography to circumvent such policies and pass messages covertly. Commercial applications of steganography in the form of digital watermarks and digital fingerprinting are currently being used to track the copyright and ownership of electronic media. Understanding and investigating the limitations of these applications helps to direct researchers to better, more robust solutions. Efforts in devising more robust watermarks are essential to ensure the survivability of embedded information such as copyright and licensing information. Tools that test the survivability of watermarks are essential for the evolution of stronger watermarking techniques. Using these tools and methods described in this paper, potential consumers of digital watermarking tools, can see how much (or how little) effort is required to make the watermark unreadable by the watermarking tools.
Perhaps an inherent weakness in many watermark approaches, is the advertisement that an invisible watermark exists in a file. With steganography, if the embedded message is not advertised, casual users will not know it even exists and therefore will not attempt to remove the mark. However, advertising the fact that some hidden information exists, is only an invitation to "crackers" as a challenge. Some watermarking tools are distributed with over-the-shelf software, such as Adobe Photoshop� [Dig]. A method was recently advertised over the Internet that such a tool has been "cracked" and showed how to watermark any image with the ID of someone else. Almost any information can be added which can even be used to overwrite valid watermarks with "forged" ones. If humanly imperceptible information is embedded within a cover, then humanly imperceptible alterations can be made to the cover which destroys the embedded information."