Although much of the steganography in use today is quite high tech, many low-tech methods exist. One common low-tech steganography method is null cipher, in which you use the first letter (or another fixed letter) of each word to form a hidden message in otherwise innocuous text. For example, a spy might have sent the following cablegram during World War I (WWI):
PRESIDENT'S EMBARGO RULING SHOULD HAVE IMMEDIATE NOTICE. GRAVE SITUATION AFFECTING INTERNATIONAL LAW. STATEMENT FORESHADOWS RUIN OF MANY NEUTRALS. YELLOW JOURNALS UNIFYING NATIONAL EXCITEMENT IMMENSELY.
The first letters of each word form the following character string: PERSHINGSAILSFROMNYJUNEI. A little imagination and a few spaces yield the real message: PERSHING SAILS FROM NY JUNE I.
Another low-tech form of steganography uses a template (e.g., a piece of paper with holes cut in it) or a set of preselected locations on a page to hide a message. In this case, the sender and receiver must use the same template or rules. Alternatives to the template method include
- pinpricks in maps, which you use as an overlay to mark letters
- deliberate misspellings to mark words
- small changes in spacing to mark hidden letters or words
- a slightly different font to mark relevant letters or words (e.g., the difference between Courier and Courier New isn't noticeable unless you're looking for it)
Steganography doesn't apply just to written forms of communication. You can use radio and television broadcasts to hide messages. For example, some government sources suspect that Osama bin Laden's prerecorded videotapes, which television stations around the world have played, contain hidden messages.
Some steganographers believe that the code the United States Marine Corps Navaho Code Talkers of World War II (WWII) used represents a form of steganography. The messages weren't encrypted; rather, the plaintext was simply in a language that the Japanese didn't know.
One of the oldest forms of steganography is to shave a messenger's head and tattoo a message on it. After the hair grows back, the messenger goes to the intended recipient, who shaves the messenger's head to recover the message. This method is clever, very low tech, and goes right to the heart of steganography's literal meaning of covered writing.