User Manual |

10. Decoding a real message |

Contents of this page |

10.1 Introduction 10.2 Intercept form 10.3 A decoded message 10.4 Decoding your first message

10.1 Introduction |

During WWII, the Germans sent hundreds of messages each day on each encryption key. These messages were intercepted by a large number of listening stations alng the British coast line, the so called Y-Stations. Once recorded on paper, the messages were sent to Blechley Park, initially by motor courier and later by teleprinter. Once at Bletchley Park, the messages were decoded and filed in a huge archive for later reference. Although hundreds of thousands of messages were present in the BP archives towards the end of the war, not many are available today. Instructed by Churchil himself, all documents and equipment in BP was destroyed as he didn't want anyone to find out what had happened during the war. Today, only a few original messages have been retrieved from the Public Record Office (PRO) in the UK, some of which are presented here.

10.2 Intercept form |

Enigma messages were sent by the Germans in morse code. Operators in the Y-Stations, intercepted these messages and wrote them down on paper forms. Initially, these paper messages were transported to BP by a courier, but later in the war they used a teleprinter over secure telephone lines. Here is example of an original message as received by BP. The one on the left is the intercept which was processed by many departments at BP, hence the many marks and codes added to it. The message is encrypted with the RED key of 31 Octiber 1944 and was received at BP on 1 November 1944. The image on the right shows the back of the reception form. Once the key for that day was broken, a modified Type-X machine (the British equivalent of an Enigma) was used to decipher the message. The decoded message was printed on a paper tape that was then glued to the rear of the message. |  |

A German speaking British intelligence officer then interpreted the message. In this particular message, spaces are replaced by an X, whilst YY is used to indicate a new line. As can be seen in this example, there were many mistakes in the text, either caused by spelling mistakes on behalf of the German operator or errors in taking the morse code by the Y-Station operator, which made the decryption of the message even more difficult.

10.3 A decoded message |

Below is an example of an original message and the decoded text. The message is dated 21 September 1938 (that's before the war!) and was sent in three parts. Thanks to Frode Weierud for his kind permission to reproduce the original message, the explanation and the translation. The markings above each of the three message blocks (AGI, YBE and LUN) have been added with a pencil to indicate the wheel settings at the start of that block). Fernschreiben H.F.M.No. 563

`+ HRKM 13617 1807 - AN HEERESGRUPPENKOMMANDO 2= 06 18 24 (FRX) 2109 -1750 - 3 TLE - FRX FRX - 1TL -172= 01 07 09 (AGI) HCALN UQKRQ AXPWT WUQTZ KFXZO MJFOY RHYZW VBXYS IWMMV WBLEB DMWUW BTVHM RFLKS DCCEX IYPAH RMPZI OVBBR VLNHZ UPOSY EIPWJ TUGYO SLAOX RHKVC HQOSV DTRBP DJEUK SBBXH TYGVH GFICA CVGUV OQFAQ WBKXZ JSQJF ZPEVJ RO - 2TL - 166 - 25 02 05 (YBE)25 02 05 (YBE) ZZWTV SYBDO YDTEC DMVWQ KWJPZ OCZJW XOFWP XWGAR KLRLX TOFCD SZHEV INQWI NRMBS QPTCK LKCQR MTYVG UQODM EIEUT VSQFI MWORP RPLHG XKMCM PASOM YRORP CVICA HUEAF BZNVR VZWXX MTWOE GIEBS ZZQIU JAPGN FJXDK I - 3TL - 176 - 12 21 14 (LUN) DHHAO FWQQM EIHBF BMHTT YFBHK YYXJK IXKDF RTSHB HLUEJ MFLAC ZRJDL CJZVK HFBYL GFSEW NRSGS KHLFW JKLLZ TFMWD QDQQV JUTJS VPRDE MUVPM BPBXX USOPG IVHFC ISGPY IYKST VQUIO CAVCW AKEQQ EFRVM XSLQC FPFTF SPIIU ENLUW O = 1 ABT GEN ST D H NR. 2050/38 G KDOS +`

The decoded message

`AUF BEFEHL DES OBERSTEN BEFEHLSHABERS SIND IM FALLE X Z X ZT X UNWAHRSCHEINLICHEN X FRANZOESISQEN ANGRIFFS DIE WESTBEFESTIGUNGEN JEDER ZAHLENMAESSIGEN UEBERLEGENHEIT ZUM TROTZ ZU HALTEN X FUEHRUNG UND TRUPPE MUESSEN VON DIESER EHRENPFLIQT DURQDRUNGEN SEIN X ABS X DEM GEMAESS BEHALTE IQ MIR DIE ERMAEQTIGUNG ZUR PUFGABE DER BEFESTIGUNGEN ODER AUQ VON TEILEN AUSDRUECKLIQ PERSOENLIQ VOR X ABS X AENDERUNG DER ANWEISUNG X OKH X GEN X ST X D X H X ERSTE ABT X NR X DREI DREI ZWO EINS X DREI AQT G X KDOS X VOM JULI EINS NEUN DREI AQT BLEIBT VORBEHALTEN X DER OBERBEFEHLSHABER DES HEERES`

In plain German, the message looks like this

`Auf Befehl des Obersten Befehlshabers sind im Falle, (z.Zt =) zur Zeit unwahrscheinlichen, Franzoesischen Angriffs die Westbefestigungen jeder zahlenmaessigen Ueberlegenheit zum trotz zu halten. Fuehrung und Truppe muessen von dieser Ehrenpflicht durchdrungen sein. Dem gemaess behalte ich mir die Ermaechtigung zur Aufgabe der Befestigungen oder auch von Teilen ausdruecklich persoenlich vor. Aenderungen der Anweisung OKH/Gen/St/D/H Erste Abt Nr. 3321/38 G/KDos vom Juli 1938 bleibt vorbehalten. Der Oberbefehlshaber des Heeres.`

English translation

`The Commander-in-Chief orders as follows: In the case of French attacks on the western fortifications, although unlikely at this moment, those fortifications must be held at all costs, even against numerically superior forces. Commanders and troops must be imbued with the honour of this duty. In accordance with orders, I emphasise that I alone have the right to authorise the fortifications to be abandoned in whole or part. I reserve the right to make changes to the order OKH/Gen/St/D/H 1. Abt. Nr. 3321/38 GKDos of July 1938. The Commander-in-Chief of the Army.`

Comments on the translation I am indebted to Ralph Erskine who has verified my translation and proposed various improvements. The translation has been kept as close to the German text as possible, however it is not a literal translation. It has been attempted to make the translation easily understandable in the English language and to use British Army idioms (i.e Commander-in-Chief) where applicable. The German word 'Westbefestigungen' means literally western fortifications and has been retained as such in the given translation, even if it could be interpreted to simply mean 'western front'. A major fortifications in this sector was the French Maginot Line, but the message clearly does not refer to this. It is therefore likely that it is the 'West Wall' or the Siegfried line which the message refers to. According to "The Oxford Companion to the Second World War" the construction started in 1936 and accelerated in 1938 when the Todt Organization employed 500,000 workers and consumed one-third of Germany's annual output of cement to complete it. It eventually ran for 300 miles (480 km), opposite the Maginot line. Copyright 1998, Frode Weierud

10.4 Decoding your first message |

It's about time you decode your first real German message. Although the situation described here is in the context of a Kriegsmarine message of 1945, we've taken certain liberties with history by using a simpler message key employed by the German army in 1939. The reason for this is that the Naval key system is far too complex to describe in this simple example. Reprinted here with kind permission of David Hamer. You are the radioman on U-516 that departed Kristiansand, Norway on 16 April 1945. The date is now 30 April 1945. The Radio Officer het set your Enigma M4 to the daily settings, which are:

Umkehrwalze | 'Thin' C
Walzenlage | Gamma, II, I, V
Ringstellung | ASOD
Grundstellung | AMZI
Steckerbrett | AD LR ZJ XI BU KV SW FH EN MY

The following enciphered message has been received:

`HRQN SMAD LVIO DMMW JLKN GSRJ VNLC IKGT MDRB IDAW YLIK IFIF CMCG HRQN SMAD`

Set AMZI in the windows and enter the first two-letter groups of the ciphertext. This will reveal the message key in duplicate. Next set the four wheels of your Enigma to this key and decipher the remainder of the message. Just to give you a clue: the first word LVI should translate to the German word der, so if you don't get this, think again! The final pair of 4 letter groups is a repeat of the enciphered message (Kriegsmarine SOP) and may be ignored. If a lamp fails to light or if you key in the wrong ciphertext letter, ignore it and proceed to the next ciphertext character. Do not re-enter the character that was wrongly keyed or the rest of the plaintext will be meaningless. Good luck! Hals und Beinbruch!

© Copyright Paul Reuvers. Last changed: Mon,18 Aug 2003.08:27:48