Overview of Steganography

Steganogrphy refers to the science of “invisible” communication. The word stega derived from Greek word stegos or roof which refers to covered and nography derived from the same Greek word graphia which refers to writing. Its purpose is to hide the very presence of communication by embedding messages into “innocent looking” cover objects. It is based on replacing the least significant bit in image, music, or video files with the concealed message data. It can be used in a large amount of data formats in the digital world of today. The most popular data formats used are .bmp, .doc, .gif, .jpeg, .mp3, .txt, and .wav. Steganography in short is hiding a secret message inside in an ordinary message.

Background

The rise of the internet is one of the most important factors of information technology and communication has been the security of information.  Cryptography was created as a technique for securing the secrecy of communication and many different methods have been developed to encrypt and decrypt data in order to keep the message secret.  Unfortunately it is sometimes not enough to keep the contents of a message secret, it may also be necessary to keep the existence of the message secret.  The technique used to implement this is called Steganography.  Steganography is the art and science of invisible communication. This is accomplished through hiding information in other information, thus hiding the existence of communication information.

Steganography is mostly used on computers with digital data being the carriers and networks being the high speed delivery channels.  Steganography focuses on keeping the existence of a message secret.

Research in Steganography has mainly been driven by a lack of strength in cryptographic systems.  Many governments have created laws to either limit the strength of a cryptographic system or to prohibit it altogether forcing people to study other methods of secure information transfer.  Business has also started to realize the potentials of Steganography in communicating trade secrets or new product information.  This study intends to offer a stage of the art overview of the different algorithms used for image Steganography to illustrate the security potential of Steganography for business and personal use.

Evolution of Steganography

Steganogrphy has been used to secretly communicate information between different users.

• During World War 2 invisible ink was used to write information on pieces of paper so that the paper appeared to the average person as just being blank pieces of paper.
• In action Greece they used to select messengers and shave their head, they would then write a message on their head. Once the message had been written the hair was allowed to grow back. After the hair grew back the messenger was sent to deliver the message the recipient would shave off the messengers’ hair to see the secret message. 
• Another method used in Greece was where someone would peel wax off a tablet that was covered in wax, write a message underneath the wax then re-apply the wax. The recipient of the message would simply remove the wax from the tablet to view the message.

Carrier File refers to a file which has hidden information inside of it. Steganalysis means the process of detecting hidden information inside of a file. Stego-Medium is the medium in which the information is hidden. Redundant Bits are piece of information inside a file which can be “overwritten (or) altered” without damaging the file and payload said to be the information which is concealed.

Modern Terminology