n4ze3m.comsource ↗
German Army Enigma · 20 July 1941 · Spruch 242

JBIYH

55 letters. No key, no crib. Broken 8 October 2026.

27.4 M rotor positions1 × RTX 409044.5 minranked #1 of 23,878
01 · the message

Decrypt it here

An Enigma I running in your browser with the recovered key.

BSB
indicator BSB NTK

WEGEN FERNSPRECHSTOERUNG TAGESMELDUNG SOFORT DURCH FUNK HIERHER

“Telephone line down. Send the daily report here by radio, now.”

ReflectorB
WheelsV IV I
RingsE X T
PlugboardAU BI CY ET FL HK MP NR OX QV
Message keyTZU
02 · the method

Anneal every rotor position

No guessed words. Simulated annealing on the plugboard at every position, then rescore what survives.

27,418,560
rotor positions, all 60 wheel orders
GPU · 128 anneals each
2,147,043
plugboards that look like German
n-gram score
23,878
rescored by words, indicator, lazy key
CPU · stage 2
1
reads as German
V IV I · EXT · TZU
03 · the signal

The score couldn't find it. The evidence could.

14,877th

by n-gram score alone

1st

by combined evidence: 25.1 vs 19.85 for the next

Evidence scores of all 23,878 candidates Nearly every candidate scores between 0 and 19. One row, the real key, scores 25.1. 1 10 100 1,000 10,000 evidence 0–1: 98 rows evidence 1–2: 417 rows evidence 2–3: 1,159 rows evidence 3–4: 1,958 rows evidence 4–5: 2,330 rows evidence 5–6: 2,103 rows evidence 6–7: 1,840 rows evidence 7–8: 545 rows evidence 8–9: 1,339 rows evidence 9–10: 704 rows evidence 10–11: 457 rows evidence 11–12: 6,661 rows evidence 12–13: 2,497 rows evidence 13–14: 431 rows evidence 14–15: 844 rows evidence 15–16: 354 rows evidence 16–17: 66 rows evidence 17–18: 53 rows evidence 18–19: 12 rows evidence 19–20: 9 rows evidence 25–26: 1 row 0 5 10 15 20 25 the real key evidence score rows (log)
04 · 1941 radio noise

Five letters misheard in Morse

The receiving operator wrote down a few wrong letters. Three are one lost dot or dash.

pos 7
L → T
.-.. vs -
pos 10
G → Q
--. vs --.-
pos 11
K → Q
-.- vs --.-
pos 25
R → E
.-. vs .
pos 50
R → L
.-. vs .-..
05 · the source

The original form

The full 1941 Funkspruch form for message 242: sender A.K., recipient Ib, received 20.7.41 at 23:37, with the handwritten cipher groups.
Spruch 242, A.K. → Ib, received 23:37. Bundesarchiv, via CryptoCellar.
The plugboard of an Enigma machine with cables connecting pairs of letter sockets.
The plugboard: 150 trillion settings with 10 cables. Photo: Bob Lord, CC BY-SA 3.0.
Enigma rotors on their spindle, showing contacts, ratchets and notches.
Rotors. Photo: TedColes, public domain.
06 · verify

Check it yourself

git clone https://github.com/n4ze3m/enigma-jbiyh-break.git
cd enigma-jbiyh-break
python3 verify.py   # decrypts JBIYH with the recovered key
Source ↗CUDA kernel, scorer, data. MIT. CryptoCellar ↗Listed broken “by Muhammed Nazeem (AI) on 08.10.2026” Ostwald & Weierud ↗Modern Breaking of Enigma Ciphertexts, Cryptologia 2017