In the days of 1795, one of America’s greatest inventors, Thomas Jefferson, came up with a cipher system that was later used by the United States Army from 1923 until 1942. The Army, however, never knew about Jefferson’s invention; it took the liberty of re-inventing it! Jefferson was over a hundred years ahead of his time.

In order to make his cipher, Jefferson used 26 wheels, each with the letters of the alphabet arranged randomly around them. The key to this system was how the wheels were ordered around the axis. The user could devise a code word which corresponded to the ordering of the wheels. Once the order is devised, you can move the rows up and down until the message is spelled out. Then looking across, the user can copy any row of text other than the one that contains the message. The recipient simply has to get the discs in the correct order, spell out the encrypted message, and then look around until he sees the plain message right before his eyes! There is an extremely small chance that there would be two readable messages, but that can be checked quickly by the person coding.

This system is considered quite secure against modern codebreaking if the message is short, and the ordering of letters and wheels is not known to the codebreaker.  As messages get larger, it is easy to apply the statistics of English language letter frequency, find patterns, and break the code.

Try it yourself! Below is a representation of the wheel cipher, very similar to Jefferson’s, that the US Army used from 1923 until 1942. It is called the M-64. Follow these instructions to try and use it:

1. To change the order of the alphabet discs, enter a key word or phrase and press the Change Key buton.
2. A disc may be rotated by the mouse with click & drag.
3. To select a disc, click on it. The selected disc is marked by a red label below it.
4. You may rotate the selected discs, pressing arrow up, arrow down, page up, or page down.
5. To rotate all discs, press the Up or Down buttons. Hold down the control key while pressing arrow up, arrow down, page up, or page down will rotate all discs as well.
6. Press the Grab button or F10 to copy the line between the markers into a text area for further processing. If you hold down the shift key, all characters up to the last modified disc are copied. Without a shift key disk, all 25 characters are copied.
7. The Switch bottom toggles between the view of the cipher discs and a text display.
8. Finally, by typing a letter the selected disk will rotate to show this letter and select the next disc, if any.

EXAMPLE:

1. If it isn’t already there, enter "chinese laundry" without quotes into the text field at the bottom. Press "Change Key."
2. Put your mouse over the first column of letters, and click the left button.
3. Type the following exactly as it appears here, without spaces: