Plaintext message may hide in one of two ways.
Conceal the existence of the message-Steganography.
Render the message unintelligible to outsiders by various transformations of the text-Cryptography
A simple but time-consuming form of steganography is the one in which an arrangement of words or letters within an apparently normal text spells out the real message.
For example, the sequence of first letters of each word of the overall message spells out the hidden
Some other techniques that have been used historically listed below:
Character marking: Selected letters of printed or typewritten text overwritten in pencil. The marks are ordinarily not visible unless the paper held at an angle to the bright light.
Invisible ink: A number of substances can use for writing but leave no visible trace until heat or some chemical applied to the paper.
Pin punctures: Small pin punctures on selected letters ordinarily not visible unless the paper is held up in front of a light.
Typewriter correction ribbon: Used between lines typed with a black ribbon, the results of typing with the correction tape are visible only under a strong light.
Although these techniques may seem ancient, they have modern equivalents.
For example, suppose an image has a resolution of 2048 X 3072 pixels where each pixel denoted by 24 bits (Kodak CD photo format).
The least significant bit of each 24-bit pixel can change without greatly affecting the quality of the
The result is that you can hide a 2.3-megabyte message in a single digital snapshot.
There are now a number of software packages available that take this type of approach to
Steganography has a number of drawbacks when compared to encryption.
It requires a lot of overhead to hide a relatively few bit of information.
Once the system discovered, it becomes virtually worthless.
The advantage of steganography is that it can employ by parties. Who has something to lose if the fact of their secret communication discovered.