This instructible will demonstrate basic steganography by showing you how to hide one image in another.
For these instructions you will need:Gimp
one image to hide,
one image to hide the other.
Step 1: A little bit about steganography
Steganography is the act of hiding information in something else. It is favorable over encryption because encryption only obscures the meaning of the information, steganography hides the very existence of the information, also, encrypted data tends to attract attention, which often proves fatal to any agent. This art (for lack of a better phrase) has been around for centuries, and has many forms, one common low-tech method is simple invisible ink, another, ancient method involved tattooing the information on the top of someone's head and allowing hair to grow over it. My favorite example is the artwork of Lord Baden-Powell, in which he hid the maps and plans of an enemy base in drawings of insects and leaves while posing as a naturalist.
The method i will show you hides an image by modifying each pixel in it's host. It only changes the least significant bits of each pixel, this means it makes tiny changes that are unnoticeable to a person.