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Caesar Box
Strip cipher

One of the most basic methods for exchanging encrypted messages, is a substitution cipher. In its simplest form, it is often called Caesar Cipher as he was one of the first to use it for communication with his army. Caesar decided that in his messages, each letter would be shifted 3 positions to the right (i.e. A becomes D, B becomes E, etc.). For this reason, the Caesar Cipher is also called a Shift Cipher, since the ciphertext is derived from the plaintext by shifting each letter a fixed number of positions.
 
At the height of the Cold War, crypto experts and code breakers in many western countries were trained by the army. As part of their training, they had to learn the basic skills of Shift Ciphers and Substitution Ciphers, and variations thereof.

One such example is the so-called Caesar Box shown here. It was developed by the Dutch Army for instruction purposes, probably in the early 1970s. [1] The box consists of a wide variety of alphabet strips; white strips with the Latin alphabet and yellow strips with Cyrillic (Russian). Blank strips are supplied to allow alternative alphabets to be used.
  
The contents of the Caesar Box
Caesar Box courtesy of DIVI [1]


Each strip contains the alphabet twice, to allow for wrapping at the end. The letters are printed in black, but the high-frequency letters are printed in red. As the frequency distribution of the letters is different for each language, spearate sets of strips are supplied, covering the common western languages. A set of 15 alphabet strips can be placed in a special transparent holder, allowing the strips to be moved from left to right (see image), in a similar manner to a slide ruler. For this reason, such systems are sometimes called alphabet slide rulers.

Please note that Caesar Box is just a nickname for the wooden instruction box above. It should not be confused with the Caesar Box Cipher which is yet another cipher method. The latter works by writing out the text in a matrix and then reading out the matrix in a different direction (check the links below).
 
The closed Caesar Box First peek inside the box The contents of the Caesar Box The slide ruler with 15 alphabet strips Close-up of the slide ruler Close-up of a standard (Latin) alphabet strip Close-up of a yellow Cyrillic alphabet strip Blank alphabet strip

 
References
  1. Dutch Department of Defense, Defensie Inlichtingen en Veiligheids Instituut (DIVI)
    Caesar Box courtesy of DIVI, donated in 2010.

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Crypto Museum. Last changed: Friday, 04 September 2015 - 06:05 CET.
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