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Tool to decrypt/encrypt with ADFGVX. ADFGVX is a German encryption system unsing a 6x6 square grid and letters A,D,F,G,V,X and then this ciphertext get a permutation of its letters (transposition).

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Tag(s) : Substitution Cipher, Transposition Cipher

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### Without knowing the grid

Tool to decrypt/encrypt with ADFGVX. ADFGVX is a German encryption system unsing a 6x6 square grid and letters A,D,F,G,V,X and then this ciphertext get a permutation of its letters (transposition).

### How to encrypt using ADFGVX cipher

The encryption uses a 6x6 square grid of 36 distinct characters (usually the latin alphabet and the 10 digits from 0 to 9). Lines and columns named, from top to bottom and from left to right, by the letters A, D, F, G, V and X. Each character of the plain text must exist in the grid in order to be localized by a coordinate (line, column).

Example: A grid filled with AZERTYUIOPQSDFGHJKLMWXCVBN0123456789: such as A = (A,A), B = (V,A), C = (G,V), D = (F,A) etc.

A D F G V X \ A Z E R T Y U I O P Q S D F G H J K L M W X C V B N 0 1 2 3 4 5 6 7 8 9

By replacing each letter of the message with the pair of coordinates, the intermediate ciphered message is then a substitution with bigrams.

Example: DCODE becomes FA,GV,DF,FA,AF

This message will get another encryption by columnar transposition. The transposition uses a permutation key/keyphrase, usually based on a keyword. This can be found it by rearranging its letters in alphabetic order. Two same letters are ranked in order of appearance, but if possible avoid duplicates letters in the keyphrase as this can lead to encryption/decryption errors.

Example: KEY => K(1),E(2),Y(3) => E(2),K(1),Y(3) => 2,1,3

The message is written in a table whose width is the key size. Empty box are filled with X (or another letter).

Example:

K(1)E(2)Y(3)
FAG
VDF
FAA
Fxx

Columns are rearranged such as the permutation key.

Example: Column 1 (K) switches with column 2 (E)

E(2)K(1)Y(3)
AFG
DVF
AFA
xFx

The final ciphertext is created by reading the letters of the table by columns starting from top to bottom and from left to right.

Example: Final encrypted message is ADAXFVFFGFAX (message often transmitted in Morse code)

### How to decrypt ADFGVX cipher

The ADFGVX decryption process requires a key and a grid.

Example: The cipher text is AD,AX,FV,FF,GF,AX and the keyword is KEY (that correspond to permutation K(1),E(2),Y(3) => E(2),K(1),Y(3) => 2,1,3)

The ciphered message is then written from top to bottom and from left to right in a table with $n$ columns where $n$ is the length of the key. Columns are named according to the letters of the key, rearranged in alphabetic order.

Example:

E(2)K(1)Y(3)
AFG
DVF
AFA
XF

The table gets a permutation of its columns according to the permutation key in order to get back the original order of the keyword's letters.

Example:

K(1)E(2)Y(3)
FAG
VDF
FAA
F

Reading the table by row gives the intermediate message.

Example: FAGVDFFAAFXX.

For each bigrams, replace it with the corresponding letter with coordinates (line, column) in the grid to get the plain text message.

Example:

A D F G V X \ A Z E R T Y U I O P Q S D F G H J K L M W X C V B N 0 1 2 3 4 5 6 7 8 9

Example: FA = line F, column A = D then GV = C, etc. The original plain text is DCODE.

### How to recognize an ADFGVX ciphertext?

The ciphertext must contain only 6 distinct characters: A, D, F, G, V and X.

Theorically, the ciphered message should have number of character that is divisible by the permutation key length.

### How to recognize a non-permuted text?

If the ciphertext hasn't be permuted, the text is a bigrammic substitution. After a substitution by a random alphabet, the text should have a correct index of coincidence.

### How to decipher ADFGVX without key for permutation?

One can crack ADFGVX and find the permutation order without knowing the key by bruteforcing all possible permutation. Use the Permutation Brute-force button.

### How to decipher ADFGVX without grid

One can crack ADFGVX and find the substitution grid by making a alphanumeric replacement of the bigrams resulting from the permutations. Use dCode's tool for mono-alphabetic substitution.

### How to decipher ADFGVX without key nor grid?

One can crack ADFGVX without the key nor the grid by finding first the permutation (see below) and then do an alphabetical substitution.

The letters A, D, F, G, V and X have been selected because their equivalent in morse code are very distinguishable, his prevent transmission error by radio

### When ADFGVX have been used?

ADFGVX cipher have been introduced at the end of the First World War (from 1917) by Fritz Nebel. He have been used on the 5th of March 1918 during the german attack of Paris, it was using an ADFGX version (with the letters A, D, F, G and X only).

### What is the GEDEFU 18?

GEDEFU 18 for GEheimschrift DEr FUnker 18, which can be translated in radio-operators' cipher 18 is the old name of ADFGVX cipher.

ADFGX is an ancestor of ADFGVX, a variant using a 5x5 square, on the base of the Polybius square cipher.

### Who did crack ADFGVX cipher?

The crack is attributed to Georges-Jean Painvin. Among the deciphered messages, one text was nicknamed The radiogram of the victory because it allowed France to win a battle in June 1918.

### When ADFGVX have been cracked?

George-Jean Painvin deciphered a first message in June 1918.

### What is the Roitelet Theorem?

The theorem of Roitelet is a novel by Frédéric Cathala here (link) which has as protagonist a spy during the first world war having messages encrypted with ADFGVX.

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