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Jefferson’s Cipher – Pic of the Week

This is a guest post by Kaitlyn Norris, an intern with the Law Library Office of External Relations.

Jefferson Wheel Cipher replica in Jefferson building of the Library of Congress. [Photo by Kaitlyn Norris]

Jefferson Wheel Cipher replica, photographed in his namesake building of the Library of Congress. [Photo by Kaitlyn Norris]

Thomas Jefferson was a Founding Father of the United States of America, the primary author of the Declaration of Independence, and held positions as secretary of state, vice president, and—from 1801-1809—third president of the United States. Not only was Jefferson a Founding Father, he was also an avid inventor of multiple ciphers used to encrypt confidential information. One of his best-known inventions was the Jefferson Wheel cipher—a manual polyalphabetic substitution cipher system. This cipher was a wooden wheel assembled by 36 disks strung together on a metal axle, with each disk containing every letter of the alphabet in random order, so the recipient reads the encoded message horizontally.

Since the Revolutionary War, where Jefferson relied on hand-carried mail, operatives and public officials used complex ciphers to protect sensitive information. Jefferson invented this cipher during his time as America’s minister to France in 1784-1789, because he needed a way to get his messages securely past European postmasters who opened the mail. Since this cipher was so elaborate, Americans even utilized it at the start of World War II to spread sensitive information before other intelligence communications protocols were developed. This cipher became a building block to U.S. intelligence due to its intricacy. Also, the limited availability of decoders with the correct lettering guaranteed security of the exchanged messages.

When Jefferson was President, he used many other codes and ciphers, including a nomenclator, which was 1700 words and syllables ordered by numbers, but arranged randomly. Jefferson’s cipher has been mistaken as a Vigenere cipher; however, they are not the same type of code due to differences in the way messages are encrypted and decrypted. In addition, Jefferson gave Meriwether Lewis a square table cipher in 1803, which was to be used to inform Jefferson of Lewis and William Clark’s expedition to find the Northwest Passage.

In order to decode this cipher, one person encoding the cipher holds one wheel, and the person decoding the message holds the other wheel. Other than the decoding wheels, the only necessary component is an encoded message. An encoded message appears as jumbled letters and would be meaningless to one who did not have the instructions for the cipher.

Close-up of the Jefferson Wheel Cipher replica in Jefferson building of the Library of Congress. [Photo by Kaitlyn Norris]

Close-up of the Jefferson Wheel Cipher replica. [Photo by Kaitlyn Norris]

For users to encrypt a message, they would place their message by moving the disks to the letters that would spell out their message. For example, for this photo we chose to encode the words “LAWLIBRARY” as seen at left, starting at the second disk, we placed the letters in a line. We can encrypt this message by finding another line of letters while the decoder still has our message placed correctly. For this example, we chose our encrypted message to be the letters two lines down from our message, which reads, “OIDYGOGLDAK.” We could then pass “OIDYGOGLDAK” along to anyone who has a wheel cipher so that they are able to decrypt our message. The person decoding the message will place it in the wheel and once finished inputting every letter in a horizontal line, will see a message appear in another location on the wheel. This is the decoded message.

Due to the success of this cipher, Jefferson is credited for laying the foundations of cryptography in the U.S. His trailblazing would be used for intelligence work in centuries to come.

Good Friends or Neighbors: Compurgators in Medieval Times

The following is a guest post by Dante Figueroa, a senior legal information analyst at the Law Library of Congress. Dante has contributed a number of In Custodia Legis blog posts, including on The Rehabilitation of Dante Alighieri, Seven Centuries Later, Resources and Treasures of the Italian Parliamentary Libraries,  Legislation Protecting Italian Cultural Heritage, Proposed Anti-Sect Legislation […]

The Law Library of Congress at the Annual Meeting of the American Association of Law Libraries

The following is a guest post by Elizabeth Osborne.  Beth most recently wrote about the retirement of Supreme Court Associate Justice Anthony Kennedy. Librarians at the Law Library recently returned from the 2018 American Association of Law Libraries (AALL) Annual Conference in Baltimore, Maryland.  The conference is an opportunity for legal information professionals to share knowledge and connect with colleagues from across […]

Trinity College Library in Dublin, Ireland – Pic of the Week

Carrying on the tradition of Law Library staff visiting, and taking photos of, beautiful and interesting libraries around the world, today I bring you pictures from my recent visit to the Library of Trinity College Dublin. The Trinity College Library opened in 1592 and is the largest library in Ireland, currently holding ”over 6 million printed […]

Congress.gov New, Tip, and Top for August 2018

At the end of July, Andrew wrote about the updates to Congress.gov, which included enhancements to House committee search functionality; adding a legislative interest column to the House: Legislation with Actions Related to Committees browse page; and the ability to search on legislative interest from the Committees section of the Advanced Search page. Adrienne provides more […]

Congress.gov at the Martin Luther King, Jr. National Historical Park – Pic of the Week

Summer and travel go hand in hand.  A manager who oversees Congress.gov, Bill Kellum, was visiting the Martin Luther King, Jr. National Historical Park when he noticed the following legislation from the Library of Congress website. H.R.267 – Martin Luther King, Jr. National Historical Park Act of 2017, sponsored by Representative John Lewis, became Public Law […]