Steganography is the art and science of communicating in a way which hides the the existence of the secret message communication. It aims to hide information /covered writing. Information to be protected is hidden in another data known as cover or carrier. Data containing hidden message are called as Steganos or Stegos. Steganos look like cover data and it is difficult to differentiate between them.

Steganography based communication over easily accessible platforms to prevent leakage of information.Steganography, from the Greek, means covered, or secret writing, and is a long-practised form of hiding information. Although related to cryptography, they are not the same. Steganography's intent is to hide the existence of the message, while cryptography scrambles a message so that it cannot be understood. More precisely.

EVOLUTION OF STEGANOGRAPHY

CODE BREAKERS : David Kahn's The Code breakers and Bruce Norman’s Secret

Warfare: The Battle of Codes and Ciphers recounts numerous tales of steganography .

INVISIBLE INK : An innocent letter may contain a very different message written between the lines with invisible ink.

Common sources for invisible inks are milk, vinegar, fruit juices and urine. All of these darken when heated. Later on, more sophisticated inks were developed which react to various chemicals.

MICRODOTS: The Germans developed microdot technology. Microdots are photographs the size of a printed period having the clarity of standard-sized typewritten pages. The first microdots were discovered masquerading as a period on a typed envelope carried by a German agent in 1941.

The message was not hidden, nor encrypted. It was just so small as to not draw attention to itself (for a while). Besides being so small, microdots permitted the transmission of large amounts of data including drawings and photographs.