Hiding Secrets with Steganography

The term steganography comes from the Greek words for covered writing. If, as a child, you ever wrote an invisible message in lemon juice and had your friend hold it next to a light bulb in order to watch the message magically appear, you've used steganography. When using steganography on a computer, you actually hide a message within another file. That resulting file is called a "stego file."

http://www.onlamp.com/pub/a/bsd/2003/12/04/FreeBSD_Basics.html
(OnLAMP.com, December 4, 2003)

The trick to computer steganography is to choose a file capable of hiding a message. A picture, audio, or video file is ideal for several reasons: These types of files are already compressed by an algorithm. For example, .jpeg, .mp3, .mp4, and .wav formats are all examples of compression algorithms. These files tend to be large, making it easier to find spots capable of hiding some text. These files make excellent distractors. That is, few people expect a text message to be hidden within a picture or an audio clip. If the steganographic utility does its job well, a user shouldn't notice a difference in the quality of the image or sound, even though some of the bits have been changed in order to make room for the hidden message.

Posted by Tom on December 08, 2003