First U534 Ciphertext only break
By Michael Hörenberg
P1030684After discovered the key of the day for 1.May 1945, Michael now could break the first cipher text only message. The task was to find the correct wheel order. This could be done by testing all possible wheel positions. A so called "brute force" attack. To decide whether the correct position was reached, the TBreaker software used two algorithms: The index of coincidence and a German bi- and trigramm scoring. Message No. P1030684 was the first candidate.
The TBreaker software found the correct message key (Nachrichten-Schlüssel) very fast and there it was: The first plaintext after nearly 70 years. You can proof it with your own M4 Enigma simulator. Note that some characters left garbled due to Morse-code or handwriting errors! The Germans also used many abbreviations and a special naval language. Therefore naval ENIGMA M4 messages are hard to read.
TBreaker P1030684ENIGMA M4 KEY for No. P1030684 :
Wheel positions: VYAA
Plugs: CH EJ NV OU TY LG SZ PK DI QB
Message indicator groups: BDSH FBFX
Ciphertext (without indicator groups):
Von U-4701: Mit U-4702, 4703, 2361, 2338, 13 Rot nach Westen passiert.
From U-4701: With U-4702, 4703, 2361 and 2338, passed [point] 13 Red [headed] west.