Picture Ciphers
By Maggie

Some spies use pictures as their secret messages, and you can use this same technique to send your messages. This is a good way to carry information, because even if the spy is caught, it looks like they're only carrying pictures and not secret coded messages. 

Even the simplest picture can hide an important message. One example was a spy who disguised himself as a butterfly collector. He carried lots of drawings of butterflies. Although the drawings looked like butterflies, they were really maps and plans for fortresses of the enemy.

Hiding secret messages in pictures is called steganography.  It is different than cryptography because no one knows that the hidden message even exists.  The message can be written in invisible ink and a picture or some other message can be written or drawn on top of it.   

Citations

Books