Steganography-Introduction

Steganography is the art and science of hiding communication; a

steganographic system thus embeds hidden content in unremarkable cover media so as not to arouse an eavesdropper’s suspicion. In the past, people used hidden tattoos or invisible ink to convey steganographic content. Today, computer and network technologies provide easy-to-use communication channels for steganography. Essentially,the information-hiding process in a steganographic system starts by identifying a cover medium’s redundant bits (those that can be modified without destroying that medium’s integrity).

The embedding process creates a stego medium by replacing these redundant bits with data from the hidden message. Modern steganography’s goal is to keep its mere presence undetectable, but steganographic systems—because of their invasive nature—leave behind detectable traces in the cover medium. Even if secret content is not revealed, the existence of it is: modifying the cover medium changes its statistical properties, so eavesdroppers can detect the distortions in the resulting stego medium’s statistical properties. The process of finding these distortions is called statistical steganalysis.

This article discusses existing steganographic systems and presents recent research in detecting them via statistical steganalysis. Other surveys focus on the general usage of information hiding and watermarking or else provide an overview of detection algorithms. Here, we present recent research and discuss the practical application of detection algorithms and the mechanisms for getting around them.

Steganography is a technique used to hide information within images. Using stenography, watermarks and copyrights can be placed on an image to protect the rights of its owner without altering the appearance of the image. Almost like magic, images, executable programs, and text messages can hide in images. The cover image does not appear to be altered. People look at the cover image and never suspect something is hidden. Your information is hidden in plain sight.

Steganography in History

Steganography comes from Greek and means “covered writing”. The ancient Greeks wrote text on wax-covered tablets. To pass a hidden message, a person would scrape off the wax and write the message on the underlying wood. He/She would then once again cover the wood with wax so it appeared unused. Many developments in steganography occurred during world war II. This included the development of invisible inks, microdots, and encoded messages.

While cryptography is preoccupied with the protection of the contents of a message or information, steganography concentrates on concealing the very existence of such messages from detection. The term steganography is adapted from the Greek word steganographia, meaning “covered writing”, and is taken in its modern form to mean the hiding of information inside other information [1].

Naturally these techniques date back throughout history, the main applications being in couriering information during times of war.

The Greek writer Herodotus gave a famous anecdotal account of this around 440 B.C. His tale was of a Demeratus, a Greek in the Persian court who warned Sparta of an invasion by Xerxes, the King of Persia. He did this by removing the wax from a writing tablet, scoring his message in the wood underneath, and then covering it with wax again before sending it to Sparta [1]. With the invention of digital audio and images files this has taken on a whole new meaning; creating new methods for performing “reversible data hiding” as it is often dubbed.