FTNBK broken

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Message 6438 - Posted: 15 Sep 2017, 22:26:05 UTC
Last modified: 15 Sep 2017, 22:30:42 UTC

We have found a partial decrypt of 101 letters long FTNBK message (listed as previously unbroken here: http://cryptocellar.org/bgac/GArmy_July1941.html)

There were a couple of more or less garbled partial decrypts received by the server but it was not noticed until a better solution was found, which is:

Key: B:314:HV:FQR
Plugs: AHCNDFEIKYMPOZRUSWVX
Text: standortderlndxlnkxistxkusownrussixseqsxkvxsuedweztziqxsaitskaxsagoskaxkeineapsfaellexmawhiatvmathiat

Replacing A with O in the 19th group MJKAZ->MJKOZ (http://cryptocellar.org/bgac/16071941_214.pdf ) changes the signature to mathiatvmathiat. It's possible that the plugboard connections are not 100% correct because the message is still garbled, but so far I was unable to find better solution.

I have sent info to Frode Weierud who has already confirmed that the message is broken and I hope that he will post more info soon :D
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Message 6478 - Posted: 16 Sep 2017, 19:43:55 UTC

Great news! Looking forward to get more information about the message.
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Message 6479 - Posted: 16 Sep 2017, 20:03:07 UTC - in response to Message 6438.  

I started looking at this from an earlier version which had a wrong plug connection, BP. After analyzing the plaintext I detected that this plug was wrong and that the plug MP removed many of the previous garbles. I see now that Enigma@Home already had a solution with the correct Stecker.

The message still has many garbles but I have not been able to remove those with further fiddling of the settings so they must be just garbles. I have so far not been able to find the complete Ringstellung as the indicator LMA BJJ does not give me a good solution for the rings. I have also tried LNA BJJ as the M and N are very similar on the message form, but also with a negative result.

The are two possible Ringstellungs that give the same core position GKW, which is the position the first letter is enciphered on. One solution is the one given here: Rings: AHV and Start: FQR. The other solution is: Rings: AIV and Start: GSR, which does not have the left-wheel turnover on the first key press.

The plaintext is as far as I can decipher it the following:
STANDORT DER LND X LNK X IST X KUSOW N RUSSI X SEQS X KV X
SUEDWEZTZIQ X SAITSKA X SAGOSKA X KEINE APSFAELLE X
MAWHIAT V MATHIAT

Correcting for obvious garbles I get:
STANDORT DER LNK X LNK X IST X KUSOW N RUSSI X SEQS X KM X
SUEDWESTLIQ X SAGOSKA X SAGOSKA X KEINE AUSFAELLE X
MATHIAT X MATHIAT

LNK is an abbreviation for Leichte Nachschub-Kolonne, light supply convoy. KUSOW or KUSOV is a very small village southwest of another small place called SAGOSKA or ZAGOSKA. You can find both placed marked on this map at very top close to the date 16 July:
http://cryptocellar.org/Enigma/MBEC/NO-35-9_Ostrow-Pleskau_16-19_July.jpg

I am not quite sure of the meaning of KUSOW N RUSSI. Some places in this area are called Russa or Russi such as Staraja Russa, however I don't see that this is the case here.

The meaning of the message is:
Position of LNK is Kusow (N RUSSI ?) six km southwest Sagoska. No incidents.
Mathiat.

KEINE AUSFAELLE can possibly have other meanings, but I think "no incidents" is the intended meaning here.

The signature is spelled wrong, probably by the radio officer.
Mathiat refers to Obersturmführer Friedrich Mattiat, born 9 August 1909, SS-Nr.: 327353

Best regards,
Frode
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Message 6481 - Posted: 16 Sep 2017, 20:21:31 UTC - in response to Message 6479.  

Just one small thing. I have just verified that the 19th group should indeed be MJKOZ and not MJKAZ. The handwriting is somewhat poor on this message form and originally the 'o' was interpreted as an 'a'.

Frode
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Dan Girard
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Message 6490 - Posted: 16 Sep 2017, 22:19:47 UTC - in response to Message 6479.  

I think that "N RUSSI" is most likely a garbled repeat of "X KUSOW", just as "SAITSKA" is a garbled "SAGOSKA".

Best wishes,

Dan
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Message 6501 - Posted: 17 Sep 2017, 6:47:02 UTC - in response to Message 6490.  

Yes, I think you are right Dan.
When dealing with garbles it is always very instructive to encipher the emended plaintext and compare the new ciphertext with the original one. I did so yesterday and already then I discovered that I am guilty of two more transcription errors. The 4th group should be FMQYT instead of FMQGT and the 12th group should be UIVWY instead of UJVWY. Looking at other corrected groups we discover some interesting Morse code reception errors. The 10th group should be BHRIY instead of BSRIY and the 17th group should be HQHLI instead of HQSLI. In both cases the receiving radio operator has dropped one Morse code dot and received S (...) instead of H (....), a common error when the conditions are marginal. The 13th group is more interesting as it should be KXKAK instead of KXAKK. It shows that the radio operator is receiving several characters in his head and lagging behind in writing them down, which is a good technique, but which can result in such errors when the characters are similar. The 11th group has an odd error as it should be MRYWH instead of MRYWN; H (....) instead of N (-.) has no logical explanation. For the 20th group, which should be RXLPL instead of RXLJL, we have a lengthening of a dot to a dash, which turns P (.--.) into J (.---).

Now looking at Dan's suggestion we get for the 6th group JKPKI instead of JKPCL and for the 7th group JQGMV instead of JQZOV. Here we see more receiving errors. For the 6th group one dot has been dropped giving K (-.-) instead of C (-.-.), and L (.-..) has turned into I (..). Both possible errors under bad conditions. For the 7th group we have a dropped dashes turning Z (--..) into G (-..) and O (---) into M (--), yet again common errors.

So in the end we have the following 100% correct ciphertext:
XNQAE QNZLW FMQYT XOQZV XJKBO JKPKI JQGMV FLSVJ
BHRIY MRYWH UIVWY KXKAK FMSQF BBARN KNHBR HQHLI
UVNEH MJKOZ RXLPL WISNZ Z

Which gives the following correct plaintext:
STANDORT DER LNK X LNK X IST X KUSOW X KUSOW X SEQS X
KM X SUEDWESTLIQ X SAGOSKA X SAGOSKA X KEINE AUSFAELLE
X MATHIAT X MATHIAT

I think we then are at the end emending FTNBK.

Frode
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Message 13521 - Posted: 6 Nov 2017, 18:06:52 UTC - in response to Message 6501.  
Last modified: 6 Nov 2017, 18:07:17 UTC

As a german i think the german text is like this:

Standort der Leichten Nachschub-Kolonne ist Kosow in Russland. 6Km südwestlich Sagoska. Keine Ausfälle. Mathias
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Message boards : Number crunching : FTNBK broken




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