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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.
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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.
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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).
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- Dutch Department of Defense, Defensie Inlichtingen en Veiligheids Instituut (DIVI)
Caesar Box courtesy of DIVI, donated in 2010.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Monday, 12 November 2012 - 18:06 CET
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