Throughout history, there have been a number of code and cipher systems developed to protect important information. Although many of the methods below are not used today, they are some of the most famous cipher systems ever created.

Cipher Disk - 15th Century
Cipher Wheel - 18th Century
The Signal Corp - 19th Century
The Legend of the Slave Quilts - 19th Century
German ENIGMA - 20th Century
Navy BOMBE - 20th Century

Cipher Disk:

The cipher disk was invented in 1467 by Leon Battista Alberti, a famous Italian philosopher and architect.

Alberti used two different alphabets located on concentric rings - this means one ring is inside of or on top of another. By lining up two different letters, one from each ring, he could make a simple substitution alphabet in which he could create a cipher.

For example, if he aligned the A on the outer ring with the G on the inner ring, this would make the following substitution alphabet used to encrypt a message:

OUTER RING: ABCDEFGHIJKLMNOPQRSTUVWXYZ
INNER RING: GHIJKLMNOPQRSTUVWXYZABCDEF

From there, he could encrypt his message and send it to someone who knew the secret to revealing the message.

Cipher Wheel:

The cipher wheel was thought to be invented by Thomas Jefferson during the 18th Century.

This simple cipher machine, sometimes referred to as the "Jefferson Cipher Wheel," was constructed of 36 wooden wheels of the same size mounted on an iron rod. Each wheel was marked with a scrambled alphabet and spun freely of the other 35 wheels.

To encode a message, the cryptographer would arrange the wheels until he had a 36-letter message in a single row. Then, he would look at a different horizontal row on the wheel and write those letters down and send it to his receiver.

To decipher the message, the receiver would set his cipher wheel to the ciphertext and then look at the other lines on the wheel for a message that makes sense.

The Signal Corps:

During the American Civil War, the U.S. military established the Signal Corps whose job it was to make, break, send, and receive secret messages from other Corps.

Signalmen, as they were called, communicated to each other by waving a large red and white flag from atop a tower, roof, or hill. The patterns of left and right waves using the flag (also known as WIG-WAG) created signals that could be seen for miles by both allies and enemies. Because messages could be seen by both allies and the enemy, messages were encrypted with a cipher disk before they were waved.

Encrypted Morse Code was also used to send messages to officers.

The Legend of the Slave Quilts:

There is an interesting legend that in the early and mid-1800's, slaves in America's southern states developed a secret code to help refugee slaves escape to freedom.

Some scholars have claimed that a quilted code was created using several different quilting patterns that were stitched together to send messages or provide advice. For example, seeing a Wagon Wheel pattern would tell the slaves it was time to leave, while the North Star pattern guided fleeing slaves North by way of the Northern Star.

Once the quilts were finished, they were draped over a clothesline or hung in a window so that refugee slaves could easily find their way along the escape route without drawing attention to themselves.

To learn more about the legend of the Slave Quilts visit the National Cryptologic Museum's web page!

German ENIGMA:

During World War II, the Germans created the ENIGMA, a complicated encryption machine, to keep their messages secret from their enemies.

Thought to be the most secure cipher system ever built, the ENIGMA used a combination of wired rotors and plugs to change, or encrypt, each letter as it was pressed on the keyboard. Every day, the order of the wired rotors inside the machine was switched according to a keylist - thus making it difficult for an enemy to figure out its complicated pattern.

Until the creation of the Navy Bombe, the ENIGMA's secret messages were unbreakable without a keylist.