The Enigma decrypt was accepted on a header held out of the key search

German operators wrote the machine setup data into the message header, and the original key search never used it, according to theneuron.ai's account of the investigation ^[9]. That left the header as held-out evidence. Tested afterwards, 14,829,646 possible Enigma setting combinations yielded only 923 that produced the expected header result ^[10]. One candidate in roughly 16,000 survived ^[11], and the final key still had to be identified some other way ^[10].

Those twelve doubtful positions allow 13,824 versions of the ciphertext ^[5]. That number factors as 2^9 times 3^3, which is exactly twelve prime factors, so nine of the positions had two candidate letters and three had three ^[12]. The list was written down before the answer existed ^[6].

Brute force was hopeless against the roughly 159 quintillion possible daily settings the machine offered ^[17]. Known keys from the same day did not fit, and automated searches returned nothing useful, the-decoder reports ^[18]. The crib worked because of a design flaw: Enigma never encrypts a letter as itself, so an alignment that puts a crib letter over the same ciphertext letter can be discarded at once ^[19]. At one alignment everything held, and the 68 letters outside the crib came out as German, including "Sofort Funkantwort" and "Angabe des Marschweges" ^[20]. The project builds on earlier cryptanalytic work by Frode Weierud, Geoff Sullivan and Olaf Ostwald ^[27].

Then the checks. Separate programs reproduced the message and the header result, and another verification system matched machine behaviour across 42 sample cases ^[13]. Re-encryption turned the recovered plaintext back into the original ciphertext. That check showed the calculation ran in both directions, and it did not establish the historical reading ^[15]. A second search over the published transcription found the same key, and because it reused a phrase discovered during the first recovery, the project logs it as confirmation of the first result ^[14].

The two published accounts differ on how much the header proved. the-decoder writes that a header preserved separately in the archive confirmed the settings ^[26]. theneuron.ai describes it as a check applied after the search, one that eliminated most alternatives and left the key itself unidentified ^[10].

Leffen's own argument for authenticity is the typing. The plaintext reads BTTE where BITTE belongs and WASCHBBSCH where the sender's name probably was, and he takes the errors as evidence the decryption is real, since a fabricated result would more likely be error-free ^[21]. The signature remains uncertain ^[3]. On effort, he said he put "99 times more effort into building the website that describes the problem and the solution than into actually cracking the code" ^[22].

This bar was reachable because the archive supplied a channel of evidence the search could not consult, and because the ambiguity in the source document could be enumerated and frozen before the model began producing plausible sentences. Most agent workflows have neither. The code, the search data and a working 3D Enigma simulator can be downloaded from the project page. The packages verify the calculations and replicate the key search sequence; what they leave open is the message's historical identity and whether the solution is the only possible one ^[23].