The Jefferson Wheel was one of very first cryptographic machines devised in the 1790s by Thomas Jefferson before he became the President of America. It consisted of 26 wooden wheels, each engraved with the letters of the alphabet in jumbled order on its periphery, arranged on a common axis to form a cylinder. The order of the letters on each wheel was unique and thus no two wheels were identical. These wheels were identified by a number embossed on their lateral surface. To encrypt a plaintext, the wheels were first arranged on the axis in a particular order. Each of the letters of the plain text was then located on consecutive wheels, one letter on each wheel. The wheels were rotated to such a position that the plaintext appeared in a row. Any of the other rows could be used as the cipher text. To decrypt the message, the recipient would have to know the order in which the wheels were arranged when the text was encrypted. Once the wheels were placed in this order, the cipher text was arranged in a row on the Jefferson Wheel. The recipient now had to look at all the other rows and see which one made the most sense. This row was the plain-text. It is very unlikely that more than one rows made sense.
One major disadvantage of this method of encryption was that the machine had to be previously distributed to potential recipients of the message. In an age where getting from point A to point B would easily take a month, the process was time-consuming. So Jefferson later discarded it and started using more convenient cipher systems.
In the early 19th century, a French cryptographer, Etienne Bazeries re-invented a similar device called the Bazeries Cylinder with 20 to 30 discs. Soon in 1922, the US army adopted a similar device code-named M-94. It was envisioned by Colonel Parker Hitt and implemented by Major Joseph Mauborgne. It was made of aluminium and had 25 discs. The letters on 17th disk read "ARMYOFTHEUS" along its periphery. This device was in service upto 1943. The US Navy also made use of this device under the code-name CSP488.
- Jefferson's Wheel Cipher
- Jefferson Disk Cipher - Image source (public domain)
- Jefferson's Wheel Cipher - Discovering Lewis and Clark