Machine Learning in Image Steganalysis

Chapter 1

Introduction

Steganography is the art of communicating a secret message, from Alice to Bob, in such a way that Alice's evil sister Eve cannot even tell that a secret message exists. This is (typically) done by hiding the secret message within a non-sensitive one, and Eve should believe that the non-sensitive message she can see is all there is. Steganalysis, on the contrary, is Eve's task of detecting the presence of a secret message when Alice and Bob employ steganography.

1.1 Real Threat or Hype?

A frequently asked question is Who needs steganalysis? Closely related is the question of who is using steganography. Unfortunately, satisfactory answers to these questions are harder to find.

A standard claim in the literature is that terrorist organisations use steganography to plan their operations. This claim seems to be founded on a report in USA Today, by Kelley (2001), where it was claimed that Osama bin Laden was using the Internet in an ‘e-jihad’ half a year before he became world famous in September 2001. The idea of the application is simple. Steganography, potentially, makes it possible to hide detailed plans with maps and photographs of targets within images, which can be left on public sites like e-Bay or Facebook as a kind of electronic dead-drop.

The report in USA Today was based on unnamed sources in US law enforcement, and there has been no other evidence in the public domain that terrorist organisations really are using steganography to plan their activities. ...