Steganography: Concealment Art in Digital Forensics

Introduction

Steganography is the art of hiding or concealment of secret information within an ordinary message or file. The purpose is to hide the existence of this information from a third party so as to covertly pass messages along without being detected. (1)

Throughout this report, we will discuss what a digital forensics investigator should know in relation to Steganography in electronic communication. We will talk about the history of steganography and then discuss how steganography techniques works in comparison to cryptography and digital watermarking. We will then talk about two different types of image and audio steganography methods that can be used to conceal hidden information. These methods are Least Significant Bit Insertion (LSB) and Discrete Cosine Transform (DCT). We will then talk about a tool that can be used hide and extract hidden

The word dates back to the book, “Steganographia”, which was written in the 15th century by a German man named Johannes Trithemius. Trithemius was active in the Renaissance and worked on three books which were about magic. On the surface, these books are perceived to be written about magic but secretly, Trithemius had concealed encrypted Cryptographic and Steganographic information and in a way, Steganographia was actually a case of Steganography. (2,3)

The technique of Steganography first dates to ancient Greece. A man named Histiaeus, who was being held prisoner by King Darius, had shaved the heads of his most trusted slaves and tattooed messages upon their scalp. When their hair grew back, he would send them out on a mission to deliver these messages to the leader of Miletus, Aristagoras. As a result, a revolt began and he was released. This is the earliest known method of Steganography but over the last few centuries it has being used in a variety of ways.