ADFGVX CIPHER

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ADFGVX CIPHER
>>In cryptography, the ADFGVX cipher was a field cipher used by the German Army on the Western Front during World War I. ADFGVX was in fact an extension of an earlier cipher called ADFGX.

Invented by Lieutenant Fritz Nebel (1891–1977) and introduced in March 1918, the cipher was a fractionating transposition cipher which combined a modified Polybius square with a single columnar transposition.

The cipher is named after the six possible letters used in the ciphertext: A, D, F, G, V and X. The letters were chosen deliberately because they are very different from one another in the Morse code. That reduced the possibility of operator error.

Nebel designed the cipher to provide an army on the move with encryption that was more convenient than trench codes but was still secure. In fact, the Germans believed the ADFGVX cipher was unbreakable.

The cipher is based on the 6 letters ADFGVX. In the following example the alphabet is coded with the Dutch codeword 'nachtbommenwerper'. This results in the alphabet: NACHTBOMEWRPDFGIJKLQSUVXYZ. This creates the table below with the letters ADFGVX as column headings and row identifiers:

 This creates the table below with the letters ADFGVX as column headings and row identifiers:

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The text 'attack at 1200am' translates to this:

Then, a new table is created with a key as a heading

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Then, a new table is created with a key as a heading. Let's use 'PRIVACY' as a key. Usually much longer keys or even phrases were used.

PRIVACYADDDDDADAGVGADDDAFDGVFVFADDX

The columns are sorted alphabetically, based on the keyword, and the table changes to this:

ACIPRVYDDDADDAGAGDAVDDGADDFVDDFFVAX

Then, appending the columns to each other results in this ciphertext:
DGDD DAGD DGAF ADDF DADV DVFA ADVX

With the keyword, the columns can be reconstructed and placed in the correct order. When using the original table containing the secret alphabet, the text can be deciphered.



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