Steganography

1. Introduction

Steganography conceals the fact that a message is being sent. It is a method akin to covert channels, spread spectrum communication and invisible inks which adds another step in security. A message in ciphertext may arouse suspicion while an invisible message will not.

1.1 Purpose of Paper

This paper introduces steganography by explaining what it is, providing a brief history with illustrations of some methods for implementing steganography, and comparing available software providing steganographic services. Though the forms are many, the focus of the software evaluation in this paper is on the use of images in steganography.

1.2 Structure of Paper

Section 2 will define steganography, provide a brief history, and explain various methods of steganography. Section 3 will review several software applications that provide steganographic services and mention the approaches taken. Section 4 will conclude with a brief discussion of the implications of stegaonographic technology. Section 5 will list the resources used in researching this topic and additional readings for those interested in more in-depth understanding of steganography.

2. Steganography

2.1 Definition

The word steganography literally means covered writing as derived from Greek. It includes a vast array of methods of secret communications that conceal the very existence of the message. Among these methods are invisible inks, microdots, character arrangement (other than the cryptographic methods of permutation and substitution), digital signatures, covert channels and spread-spectrum communications.

Steganography is the art of concealing the existence of information within seemingly innocuous carriers. Steganography can be viewed as akin to cryptography. Both have been used throughout recorded history as means to protect information. At times these two technologies seem to converge while the objectives of the two differ. Cryptographic techniques "scramble" messages so if intercepted, the messages cannot be understood. Steganography, in an essence, "camouflages" a message to hide its existence and make it seem "invisible" thus concealing the fact that a message is being sent altogether. An encrypted message may draw suspicion while an invisible message will not [JDJ01].

David Kahn places steganography and cryptography in a table to differentiate against the types and counter methods used. Here security is defined as methods of "protecting" information where intelligence is defined as methods of "retrieving" information

Steganography has its place in security. It is not intended to replace cryptography but supplement it. Hiding a message with steganography methods reduces the chance of a message being detected. However, if that message is also encrypted, if discovered, it must also be cracked (yet another layer of protection).