Machine Learning in Image Steganalysis

Chapter 2

Steganography and Steganalysis

Secret writing has fascinated mankind for several millennia, and it has been studied for many different reasons and motivations. The military and political purposes are obvious. The ability to convey secret messages to allies and own units without revealing them to the enemy is obviously of critical importance for any ruler. Equally important are the applications in mysticism. Literacy, in its infancy, was a privilege of the elite. Some cultures would hold the ability to create or understand written messages as a sacred gift. Secret writing, further obscuring the written word, would further elevate the inner-most circle of the elite. Evidence of this can be seen both in hieroglyphic texts in Egypt and Norse runes on the Scottish islands.

2.1 Cryptography versus Steganography

The term steganography was first coined by an occultist, namely Trithemius (c. 1500) (see also Fridrich (2009)). Over three volumes he discussed methods for encoding messages, occult powers and communication with spirits. The word ‘steganography’ is derived from the Greek words ganesh (steganos) for ‘roof’ or ‘covered’ and ganesh (grafein) ‘to write’. Covered, here, means that the message should be concealed in such a way that the uninitiated cannot tell that there is a secret message at all. Thus the very existence of the secret message is kept a secret, and the observer should think that only a mundane, innocent and non-confidential message is transmitted.

Use of steganography ...