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Challenge "The T52 Sturgeon Challenge — Part 1"

Challenge "The T52 Sturgeon Challenge — Part 1"  

  By: admin on July 13, 2019, 11:11 p.m.

The Siemens and Halske T52 was a family of German teleprinter encryption devices used during WW2. This challenge is part of a series of challenges with T52. In this challenge, you need to recover the plaintext only from a T52ab ciphertext. The key is partially known.
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Re: Challenge  

  By: D3d4lu5 on July 15, 2019, 6:41 a.m.

Something seems to be wrong.

I can't completely recover the plaintext.

Could you please check if the ciphertext can be translated correctly with the java implementation and the specified wheel parameters?

Thank you.

Re: Challenge  

  By: george4096 on July 15, 2019, 9:18 p.m.

I double checked, and with the full key including the correct wheel positions (those that are unknown), the cipher decrypts correctly with the provided simulator.

Make sure the ciphertext and the known elements of the key are properly copied from the challenge PDF. The ciphertext has exactly 112 symbols.

Also, pay attention to the Baudot notation for the ciphertext (British), and if you are using the simulator Java code, make sure to use the correct parsing method (Baudot.fromBritishNotation()).

Good luck,

George

Re: Challenge  

  By: D3d4lu5 on July 15, 2019, 10:50 p.m.

Hello George,

thanks for your reply. I did a mistake with the wheel sizes and can now decode the complete ciphertext.

But I already tried the correct 6-digit code and it was (and is) rejected by the system.

It seems there is a problem with the verificaton process.

Re: Challenge  

  By: george4096 on July 15, 2019, 11:36 p.m.

Make sure the plaintext is clean and correct.

As mentioned in the challenge PDF, all the original plaintexts are from Shakespeare, and if you have an approximate decryption, it should be easy to find the original quote and the precise punctuation, which you should expect in the decryption (with Figure Shift and Letter Shift as needed).

Re: Challenge  

  By: D3d4lu5 on July 16, 2019, 12:17 a.m.

As I said, meanwhile I have fully recovered the plaintext, but the system does not accept my solution.

And if I understand "You should enter only the 6 digits" correctly, the Shakespeare quotes including the punctuation are completely irrelevant.

Re: Challenge  

  By: george4096 on July 16, 2019, 8:10 a.m.

It is relevant in order to make sure that you have the correct key, by checking that the decrypted text is fully correct, and this is not a nearby key, that would cause errors in both the quote and more importantly, in the numerical code.

Re: Challenge  

  By: D3d4lu5 on July 16, 2019, 5:54 p.m.

It was an encoding issue due to the import in eclipse.

That's why the Baudot translation did not work properly with a slightly different translation of the punctuation symbols and the numbers only. Although I got the right key, the encoding issue led to an incorrect 6-digit number.

Sorry for the inconvenience.


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