Secret Codes Poster Elements

Photo and Image Credits and Permissions

  • Image of picture code from 1948 Bear Cub Handbook, available at
  • Image of Caesar Cipher shift by Matt_Crypto, available at released to public domain.
  • Photo of fire engine siren by David R. Tribble, available from used with permission.
  • Photo of scytale by Luringen, available from used with permission.
  • Image of Morse Code by Rhey T. Snodgrass & Victor F. Camp, available from in public domain.
  • Photo of enigma machine by Karsten Sperling, available from released to public domain.
  • Image of Paul Revere’s midnight ride, from U.S. National Archives, available from in public domain.
  • Photo of civil war signal corps kit by Pablo Jimenez-Reyes, United States Army Historical Collection, available from in public domain.

Picture Ciphers

From the 1948 Bear Cub Handbook!
Caesar Ciphers
One of the oldest ciphers is named after Julius Caesar. In a Caesar cipher, the alphabet is shifted a certain number of places and each letter in the message is replaced by the corresponding shifted letter.

What is a Code?
A code is any symbol or signal used to stand for or communicate something.

To communicate we use the code DOG

To communicate we use the code

To communicate we use the code
What is a Cipher?
A cipher is a particular type of secret code that changes each letter of a message into another letter or symbol.
The real message is called the plaintext.
The coded message is called the ciphertext.
The system of rules that describes how the plaintext letters and ciphertext letters are related is called the key.
What is Cryptography?
Cryptography is the mathematics and science of secret messages.
Cryptographers do three kinds of activities.
  • They change messages into secret messages, which is called encryption.
  • They change secret messages back into original messages, which is called decryption.
  • They figure out keys to codes and ciphers, which is called code breaking.

Secret Codes in History
In April of 1775 in Boston, Paul Revere used a very simple code to send a message to Charleston about how the British were coming.

The code involved the number of lanterns hung in the tower of the Old North Church: “One if by land, two if by sea.”
Scytale Ciphers
A scytale (SKEE-tay-LEE) is asimple cipher machine consisting of awooden staff with a strip of parchment wound around iton which is written a message. TheancientSpartans are said to have used this cipher to communicate during military campaigns. The recipient uses a staff of the samediameteron which he wraps the parchment to read the message. It has the advantage of being fast and not prone to mistakes—a necessary property when on the battlefield.
Secret Codes
Morse Code

Morse code transmits letters as a series of on-off tones, lights, or clicks that can be interpreted by a skilled listener or observer.
Secret Codes in History
During World War II, the Germans developed the ENIGMA, an encryption device to send secret messages. It was the most secure and complex cipher system ever built at the time. It took a long time for the U.S. to discover the key. /
NATO Phonetic Alphabet
This code replaces each letter with a word that begins with that letter. The replacement words are easy to tell apart from one another when spoken. This is a spoken code and is good for two-way radio communication, when static often makes it difficult to tell two similar sounding letters, like B and D, apart.
Alpha
Bravo
Charlie
Delta
Echo
Foxtrot
Golf
Hotel
India / Juliett
Kilo
Lima
Mike
November
Oscar
Papa
Quebec
Romeo / Sierra
Tango
Uniform
Victor
Whiskey
X-ray
Yankee
Zulu
Secret Codes in History
During the Civil War, both the Union and Confederate armies developed Signal Corps for the purpose of sending and receiving secret messages. They waved red and white flags from hills, towers, and roofs to send their messages. The patterns of waves, called wigs and wags, revealed the letters of the message. Since the flags could be seen by both armies, messages were encrypted with a cipher disk before being sent.