Steganography is the process of hiding one medium of communication (text, sound or image) within another so as to avoid detection. The name is derived from the Greek word steganos, meaning “covered” or “secret.”

This document will explain the concept of steganography as well as the techniques used to implement it. It will also take a look at its evolutionary history, starting with Herodotus’ description of secret messages written in wax on stone tablets in ancient Greece, to World War II’s secret double meaning Nazi messages and British Intelligence’s invisible ink. In addition, I will discuss the tools used to both hide and unhide information, a process known as Steganalysis.

Lastly, we will study some cases where steganography has been put to use, from military ones like transferring secret data without third-party detection, to commercial ones like Digital Watermarking for copyright protection, to sinister ones like the use of steganography tools by members of Osama bin Laden’s Al-Qaida terrorist network to communicate with each other surreptitiously.