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Wanted item
Slidex was a simple manual cipher system based on a matrix of fixed
words and frequently used phrases. It was introduced by the British Army
during WWII and was simultanously used by the Russians. Since then, it
has been used in many different variations.
It is not very secure and is suitable only for short-term tactical
messages.
It was also very popular during the Cold War.
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Slidex was also used by various parts of the Dutch Army during the Cold War.
The image on the right shows a typical Slidex as it was used in The Netherlands.
At the bottom of the card it is identified as card '1' of series 'A'.
The text card consists of a matrix of 12 by 17 cells. Each cell consists of
a letter or number in red and a word or phrase in black. Switching between the
red and the black text is done by using the 'SWITCH ON' and 'SWITCH OFF' cells.
Multiple ON and OFF cells are available in order to hide their frequent use.
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The text card is removable and can easily be swapped for another one with a
different layout. In the example above, the keywords on the text card are in
alphabetical order, but this was not always the case.
Slidex was introduced the British Army around 1943 and was used heavily during
operation Overlord in June 1944. It was easily broken by the Germans using
nothing but the intercepted radio messages.
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Although it is commonly assumed that Slidex was introduced by the British Army,
the Russians started using it at about the same time. Later, during the Cold
War, its use spread out to the other states of the Warsaw Pact, such as the
former DDR (East-Germany). The common German name for the system was
Sprechtafeln or Gesprächstabellen (conversation tables).
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The image on the right shows a Slidex variant with 100 cells, that was used
by the Nationale Volksarmee (NVA) in East Germany.
It was issued in 1969 and is called Parolen- und Gesprächstabelle
(expressions and conversation table).
Apparently they used a series of different
tables, as this one is called SERIE 'F'.
Inside the book are two pages. The first page contains a 10 x 10
matrix of small rectangles (cells). Inside each cell is an expression
or a complete sentence.
At the bottom left of the page it is marked as 'SERIE E'.
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Along the left side and along the top of the page is an orange plastic
sheet, that allows it to be written with a pen or pencil.
In most cases, letters or letter pairs would be written before each row
and above each column. The combination of a row/column pair would then
identify the appropriate matrix cell.
In order to further obscure the contents of the message, a numerical table
on the second page was used to convert the letters (used for the rows and
columns) into numbers. This page is marked 'SERIE F'.
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© Copyright 2009-2012, Paul Reuvers & Marc Simons. Last changed: Mon,14 May 2012.09:42:55
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