[SIGCIS-Members] Question about the Tiltman break in Lorenz cypher (1941)

Mon May 24 15:38:46 PDT 2021

Exactly!
The whole decryption sequence from 372 to 375 is correct and uses full ITA2 naming but the p.351 table uses BP…
What also confused me is that Bauer writes (p.371):
"In this appendix, the symbol ‘1’, ‘2’ and ‘3’ are used for the control characters ‘letter shift’, ’space’ and ‘figure shift’. This is in accordance with the ITA."
Very well, but he doesn’t say anything about ‘4' and ‘5’ so I assumed they were like BP figures and not ITA2 (which I did not fully know about).

Another worse issue was with Wikipedia which used The ITA2 ‘5’ character (like Bauer) but mixed with the / and 8 characters from BP!!
It listed the second message starting with JSH5N ZYMFS /883I where Bauer correctly lists it as JSH5N ZYMFS 0115I
And since it seems everybody copied on wikipedia…

I’ve since corrected the Wikipedia page by consistently using BP naming in the example.

Regards
Emmanuel

> Le 24 mai 2021 à 19:02, Mark Priestley <m.priestley at gmail.com> a écrit :
> 
> Oh, nice! So Bauer on p 372 is in fact correctly and consistently using ITA2 naming while the table on p 351 (to which the text refers us) is using BP naming? 
> 
> On Mon, 24 May 2021 at 17:15, E. Lazard <Emmanuel.Lazard at dauphine.psl.eu <mailto:Emmanuel.Lazard at dauphine.psl.eu>> wrote:
> Ok, I’ve figured it out…
> 
> Remember that the Baudot code encodes 26 letters and 6 control characters. Now when giving a list of characters (message, key, ciphertext…), one must find a way to express these characters by a symbol, so Bletchley Park had their well-known convention. It is NOT the one used in all examples of the Tiltman break… So the 5 in the first ciphertext is in fact NOT the 5 used at Bletchley Park (which had the meaning of shifting into figures mode). So what could it means? It’s one of the ITA2 naming…
> 
>  bits  name        ITA2   BP
> 00000 NULL           0    /
> 00010 Carriage Ret.  4    3
> 00100 Space          2    9
> 01000 Line Feed      5    4
> 11011 figures        3    5 or +
> 11111 letters        1    8 or - 
> 
> Now, what’s very confusing is that the addition table given on page 351 of the Copeland book uses the Bletchley Park convention.
> 
> So either use the ITA2 naming but then you must use the ITA2 addition rules, or use the Bletchley Park naming for both, but do not mix them!
> 
> Emmanuel
> 
> 
> 
> 
>> Le 24 mai 2021 à 16:27, Mark Priestley <m.priestley at gmail.com <mailto:m.priestley at gmail.com>> a écrit :
>> 
>> Emmanuel - 
>> 
>> I don't know if the cyphertexts have been wrongly transcribed or not, but for sure Friedrich Bauer made a slip when he added them together, as I described in my earlier post (did you see that?).
>> 
>> If the originals exists, they might be in the Bletchley Park archives. Their website https://bletchleypark.org.uk/ <https://bletchleypark.org.uk/> has some information about their collections and archives, and contact details.
>> 
>> Best
>> Mark
>> 
>> 
>> On Mon, 24 May 2021 at 14:41, E. Lazard <Emmanuel.Lazard at dauphine.psl.eu <mailto:Emmanuel.Lazard at dauphine.psl.eu>> wrote:
>> Many thanks for your answers.
>> 
>>> Le 24 mai 2021 à 04:38, thomas.haigh at gmail.com <mailto:thomas.haigh at gmail.com> a écrit :
>>> 
>>> I wonder if the problem is in part that Copeland got the teleprinter character set wrong. Some years ago I was working from the version given in his appendix when trying to understand the quirks in the interaction of German and the teleprinter code that explained why the deltas between the bit patterns for successive characters were both much more likely to be 0 than 1. That is what underpinned Tutte's method, used by Colossus, which exploited the fact that the deltas between successive characters were not fully scrambled by the Lorenz equipment. So there was a clear statistical signature that marked the correct positions for the first two "Chi wheels." (That analysis underpinned my attempt to give an accurate but non-mathematical account of the process in https://cacm.acm.org/magazines/2017/1/211102-colossal-genius/fulltext <https://cacm.acm.org/magazines/2017/1/211102-colossal-genius/fulltext>).
>>>  
>>> I was having some difficulty in squaring tables in archival reports giving the most common two letter sequences in the encoded messages with the bit patterns for the deltas between them. Then I realized, or my collaborator Mark Priestley pointed out, that the discrepancies were caused by errors in the teleprinter alphabet Copeland included as appendix 2 on pages 248-9. Five years on I can’t remember if there was just one error or several. But I do remember that the frequency of EI in the plaintext was very high so I just  rechecked that his entries for those letters. I see that the code Copeland gives for I (oxxox) does not match the one given at https://en.wikipedia.org/wiki/Baudot_code <https://en.wikipedia.org/wiki/Baudot_code>. The other clue is that Copeland has the same bit pattern in successive lines, identified first as coding P and then as coding I. They can't both be right. 
>>>  
>>> Looking at the https://billtuttememorial.org.uk/codebreaking/teleprinter-code/ <https://billtuttememorial.org.uk/codebreaking/teleprinter-code/> page that Emmanuel mentions, I notice a similarly blatant error: the page identifies both M and N as being coded by (ooxxx). Which doesn't match Copeland or Wikipedia. So it appears that both the Tutte fan site and the Copeland book present incorrect teleprinter alphabets.
>> 
>> I’ve checked in my copy of the Copeland book and indeed, the I code isn’t correct:  it’s given as •xx•x (same as P) but it should be •xx••. 
>> It’s the only mistake in the book (concerning the Baudot code) and it doesn’t solve my issue where I isn’t involved…
>> 
>> 
>>>  Hence Emanuel shouldn't discount the possibility that the cyphertexts are correct but the teleprinter code to bit conversions are wrongly given in both the sources he is relying on. Having said that, given the rather low standards of proofreading we're seeing here it wouldn't shock me if the cypher text sequences were also given wrongly in Copeland and copied from one website to another with errors included. I don't have time to check back to primary sources, but if I was doing serious work on the technicalities of this, I'd either dig into the archival sources or at least work as much as possible from Reeds, James A., Whitfield Diffie, and J V Field. Breaking Teleprinter Ciphers at Bletchley Park. An Edition of General Report on Tunny With Emphasis on Statistical Methods (1945). Piscataway, NJ: IEEE Press/Wiley, 2015  (https://www.amazon.com/Breaking-Teleprinter-Ciphers-Bletchley-Park/dp/0470465891 <https://www.amazon.com/Breaking-Teleprinter-Ciphers-Bletchley-Park/dp/0470465891>). This is a heavily annotated and supplemented reprint of a formerly secret report written as the operation was being wound down at the end of the war. Chapter 41-44 give a thorough description of the original methods used prior to mechanization. (Though not, as far as I can see on a quick look, the full text of the messages in question).
>>>  
>>> Regarding one of Brian's comments, IIRC "addition" was simply what the BP staff called the operation we're more used to thinking of as XOR. So that might not be a source of error. They also spoke of dots and crosses rather than 1 and 0. It’s just more natural for us today to XOR 1s and 0s than to add dots and crosses. Brian is right about the shift codes, which helped to create some of the regularities in the deltas exploited by the codebreakers. IIRC, however, the shift codes get encrypted just like the other characters, rather than being stripped out by the Lorenz equipment prior to encryption as he suggests.
>> 
>> Brian’s code is just a NOT-XOR, which is just symmetrical. For the operations, exchanging 1’s and 0’s is completely irrelevant, so using XOR or its opposite doesn’t change anything.
>> 
>> So I’m more and more convinced that the ciphertexts have been wrongly given and copied from one website to the other… I’ve of course read the "general report on Tunny" but unfortunately, the ciphertexts are not given in it. So I guess I would have to dig through the archives… Any idea whom I may contact?
>> 
>> Regards
>> Emmanuel
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>>  
>>> -----Original Message-----
>>> From: Members <members-bounces at lists.sigcis.org <mailto:members-bounces at lists.sigcis.org>> On Behalf Of Brian E Carpenter
>>> Sent: Sunday, May 23, 2021 6:52 PM
>>> To: E. Lazard <Emmanuel.Lazard at dauphine.psl.eu <mailto:Emmanuel.Lazard at dauphine.psl.eu>>; members at sigcis.org <mailto:members at sigcis.org>
>>> Subject: Re: [SIGCIS-Members] Question about the Tiltman break in Lorenz cypher (1941)
>>>  
>>> Emmanuel,
>>>  
>>> On 24-May-21 09:47, E. Lazard wrote:
>>> > Dear all,
>>> > 
>>> > I’m looking for some original information on the famous "Tiltman break" which led to the cryptanalysis of the Lorenz cipher en 1941.
>>> > (https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher <https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher>
>>> > <https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher <https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher>>)
>>> > (http://www.eprg.org/computerphile/lorenz-combined.pdf <http://www.eprg.org/computerphile/lorenz-combined.pdf>
>>> > <http://www.eprg.org/computerphile/lorenz-combined.pdf <http://www.eprg.org/computerphile/lorenz-combined.pdf>>)
>>> > 
>>> > The story is: the British intercepted two messages sent with the same key (HQIBPEXEZMUG) also called a "depth".
>>> > When adding the two cipher texts with the exclusive-or function, the key cancels out and what is left is the exclusive-or of the two plain texts.
>>> > From there, brigadier John Tiltman found the two messages by trying various likely pieces of plaintext and found that the first message started with the word SPRUCHNUMMER (message number) and that the second message also used the same word but shortened out as SPRUCHNR.
>>> > 
>>> > EVERY SINGLE WEBSITE and the Copeland book "Colossus" list the two intercepted cypher texts as:
>>> > 
>>> > C1 = JSH5N ZYMFS 01151 VKU1Y U4NCE JEGPB
>>> > C2 = JSH5N ZYZY5 GLFRG XO5SQ 5DA1J JHD5O
>>> > 
>>> > and their exclusive-or as:
>>> > 
>>> > D  = ///// //FOU GF14M AQSG5 SEKZR /YWHE
>>>  
>>> Indeed,  S and 5 combine to give V according to https://billtuttememorial.org.uk/codebreaking/teleprinter-code/ <https://billtuttememorial.org.uk/codebreaking/teleprinter-code/>
>>> > My problem is that IT DOES NOT ADD UP!
>>> > The U in 10th position is not the correct result, it should be a V.
>>> > (S is 10100, 5 is 11011, so their exclusive-or is 01111 which is V)
>>>  
>>> However, there are two problems with your comment:
>>>  
>>> 1) The code for 5 is actually 11110, the same as the code for T, but in figure shift. I assume that the Lorentz system removed the figure shift and letter shift codes before starting the crypto work.
>>> 11011 is indeed the figure shift code, so the actual bit stream would have contained 11011 11110 11111.
>>>  
>>> 2) The appropriate operation is not XOR. It's what Bletchley Park called "addition", as described at the above web site. While that doesn't explain this U/V error, which I suppose started as a transcription error, it probably explains the other errors you mention.
>>>  
>>> Regards
>>>    Brian Carpenter
>>>  
>>> > And I found other issues with all examples using the cypher text, the messages, the key… I always have several letters which are wrong.
>>> > 
>>> > So I’m wondering if I’ve misunderstood something or have the cypher texts been incorrectly written down once and everybody just copied them without checking?
>>> > 
>>> > Anybody has genuine information or can point me to some source?
>>> > 
>>> > Regards
>>> > Emmanuel Lazard
>>> > 
>>> > 
>>> > 
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> _______________________________________________
> This email is relayed from members at sigcis.org <http://sigcis.org/>, the email discussion list of SHOT SIGCIS. Opinions expressed here are those of the member posting and are not reviewed, edited, or endorsed by SIGCIS. The list archives are at http://lists.sigcis.org/pipermail/members-sigcis.org/ <http://lists.sigcis.org/pipermail/members-sigcis.org/> and you can change your subscription options at http://lists.sigcis.org/listinfo.cgi/members-sigcis.org <http://lists.sigcis.org/listinfo.cgi/members-sigcis.org>_______________________________________________
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