Jefferson Disk - Cipher wheel

Philipp Kutsch

About this app

Features
✓ Interactive cipher wheel
✓ Fully configurable
✓ Share configuration with others
✓ Presets (M94, Jefferson-36)

Historic Background
Thomas Jefferson (1743-1826), the third President of the United States, is credited with the invention of one of the most advanced cryptographic devices of his time, the so-called wheel cypher.

Devised in the early-to-mid 1790s while Jefferson served as the US Secretary of State, it consisted of a system of 36 interchangeable wooden disks revolving around a central spindle, with each disk imprinted randomly with the 26 letters of the English alphabet. With the device, a 36-letter message could be encoded on one row formed by the disks and then one of the 25 remaining rows of the disk shared with a correspondent having an identical wheel cypher and a key to the order of the spindle disks.

In the late-1800s, the same system of disks was independently invented by Etienne Bazeries, a French military cryptanalyst, and subsequently formed the basis of the M-94 cipher machine used widely by US armed forces beginning in the early 1920s until the early 1940s.

Today, in addition to surplus US M-94 cipher machines collected by amateur cryptologists worldwide, a popular 12-disk, 27-character version of the Jefferson wheel cypher is sold as a wooden educational toy by the gift shops of a number of early American historical sites, including Thomas Jefferson's Monticello.