ADFGVX Cipher: Encrypt and Decrypt Online The ADFGVX cipher is a field cipher that was used by the German Army during World war 1. ADFGVX is an advanced extension of an earlier cipher called ADFGX. This cipher is a fractionating transposition cipher which combines a modified Polybius square with a single columnar transposition. The ADFGVX is named after the six possible letters used in the cipher text A, D, F, G, V and X. The six letters were specifically chosen because they were very different from one another in the Morse code. It was invented by Lieutenant Fritz Nebel to provide an army on the move with encryption that was more convenient than trench codes but still secure. Use the above ADFGVX cipher decoder and encoder to encrypt/decrypt simple messages. If this tool was helpful, tweet it or share it.