Codes require a codebook. Ciphers do not.

Union Army cipher disk

Signalling in Cipher

More info

Both armies in the Civil War used cipher disks like the one pictured above which allowed messages to be easily encoded and decoded. There was a standard flag code that gave each letter a numerical combination of 1s, flag right and 2s, flag left. Cool animation here

Freemason’s Cipher or Masonic Cipher

The Freemason’s Cipher has been around a long time. It was used in the American Civil War to send secret messages.  It is also sometimes called the Pigpen Cipher.

Read more history here. 

Try an interactive online here.

Morse Code

Until the early 1920s, radio transmissions were in Morse Code. Three things about Morse Code:

  1. Dots and dashes make it a binary code like the 0’s and 1’s used in electronics.
  2. Each letter has a signal based on its frequency in English. The code tree begins with E with one dot, and T with one dash. Then I is represented by two dots, A by a dot and dash, N with a dash and dot, M with two dashes, and so on.
  3. Morse Codebooks were used to lower the cost of sending telegrams, or to keep the contents a secret. Instead of sending a whole phrase or sentence, a single word could be used.

If you want to hear a message in Morse Code, the Morse Code translator is a great place to visit. You can type in a message, translate it to Morse Code, and play it.

Caesar Cipher


Vigenere Cipher