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Strip cipher
One of the basic encryption methods is the so-called substitution cipher.
In its simplest form, it is commonly knows as the
Caesar Cipher
as it was first used by the Roman Emperor Gaius Julius Caesar (13 July 100 BC
- 15 March 44 BC).
He 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 known as
a Shift Cipher, as the ciphertext is derived from the plaintext by shifting each letter a fixed number of positions.
Many variants of the shift cipher have been developed.
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At the height of the Cold War, cipher experts and codebreakers in many
western countries were trained by the army. As part of their training,
they had to learn the basic skills of shift ciphers,
substitution ciphers, and variations thereof.
A beautiful example is the so-called Caesar Box shown in the image
on the right. It was made by the Dutch Army – probably in the
early 1970s – for training purposes [1].
The box consists of a wide variety of alphabet strips; white strips
with the Latin alphabet and yellow strips with Cyrillic.
Blank strips are used for scrambled alphabets.
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Each strip contains the alphabet twice, to allow for wrapping at
the end of the alphabet.
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,
in a similar manner to a slide ruler.
For this reason, such systems are sometimes referred to as alphabet slide
rulers.
Note that Caesar Box is just a nickname for the wooden
instruction box featured on this page.
It should not be confused with the Caesar Box Cipher,
which is another cipher method that works by writing out the text
in a matrix and then reading out the matrix in a different direction
[3].
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© Crypto Museum. Created: Friday 12 March 2010. Last changed: Friday, 23 February 2018 - 21:54 CET.
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