ADFGX Cipher

ADFGX is a substitution cipher used during World War I by the German army. It gets its name from the letters A, D, F, G, and X, which were used to label the columns and rows of a 5x5 grid used in encryption.

The version with the letter V and a 6x6 grid, called ADFGVX, is generally better known, because it is more widespread.

Encryption is identical to the ADFGVX cipher, but it only uses 5 letters: A, D, F, G and X and so only a 5x5 grid.

As there is only 25 possible letters in the grid, one letter of the latin alphabet has to be removed, usually J and I are combined, it can also be V and W.

The decryption process is identical to the ADFGVX cipher.

The ciphertext should contains only 5 distinct characters: A, D, F, G and X.

(Optional) The ciphered message must have number of character divisible by the permutation length.

The name of the man who deciphered it is Painvin, homonym of 2 French words: bread (pain) and wine (vin), any allusion is a clue.

Any reference to Germany or its army at the beginning of the 20th century is a clue.

If the ciphertext has not be permuted, the text is a simple bigrammic substitution.

After a replacement by a random alphabet, the text should have an index of coincidence similar to the one of the plaintext language.

To crack ADFGX without a key, there is no method other than the brute-force attack (test of all possible permutations).

The substitution grid can be found by performing an alphanumeric substitution of the bigrams resulting from the encrypted text after the permutations.

See the dCode tool for mono-alphabetic substitutions.

The decoding of ADFGX without any information is complicated, but it is possible to find the permutation key first (see above) and then to perform a mono-alphabetical substitution.

The 5 letters A, D, F, G and X have been selected due to their Morse code equivalent. Indeed, their transcriptions are quite different, which avoids possible errors during radio/telegraph transmissions.

GEDEFU 18 stands for GEheimschrift DEr FUnker 18 which translates as radiotelegraphists 18 cipher is the old name of the ADFGX and ADFGVX ciphers.