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Challenge "Spanish Strip Cipher — Part 2"

Challenge "Spanish Strip Cipher — Part 2"  

  By: admin on March 27, 2014, 2:44 p.m.

An English telegram was encrypted using the Spanish Strip Cipher, a popular algorithm during the Spanish Civil War. It is your task to find the plaintext.
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Re: Challenge  

  By: george4096 on March 30, 2014, 10:08 p.m.

This is a message for the author.

I just want to make sure I fully understand the challenge:

1) Is the homophone table known or unknown?
2) Is the homophone table is unknown, then basically knowing the alphabet order is not really useful, right?

I read your master thesis, which is based on sequential use of homophones. And also a work by Campos, F.A.; Gascon, A.; Latorre, J.M.; Soler, J. R, which relies on a known homophone table. So if I understand well, none of these weaknesses is available and there is a need for a powerful generic case (all unknown) algorithm to solve the challenges, or did I misunderstand the wording of the challenge.

Many thanks
George

Re: Challenge  

  By: lbenthins on March 31, 2014, 10:10 a.m.

This is a message for the author.

I just want to make sure I fully understand the challenge:

1) Is the homophone table known or unknown?
2) Is the homophone table is unknown, then basically knowing the alphabet order is not really useful, right?

I read your master thesis, which is based on sequential use of homophones. And also a work by Campos, F.A.; Gascon, A.; Latorre, J.M.; Soler, J. R, which relies on a known homophone table. So if I understand well, none of these weaknesses is available and there is a need for a powerful generic case (all unknown) algorithm to solve the challenges, or did I misunderstand the wording of the challenge.

Many thanks
George

Hi George,

Thanks for the questions and your interest in the challenges.

1) Is the homophone table known or unknown?
Yes, in both challenges (part 1 and part 2), the homophones table is unknown.

2) Is the homophone table is unknown, then basically knowing the alphabet order is not really useful, right?
Yes, exactly.

For the first challenge (part 1) the homophones were selected sequentially, then you can use the method proposed in my thesis to reconstruct some of the columns of the homophones table (Phase 1). Beyond this point, it can be used a generic tool for solving monoalphabetic ciphers.

For the second challenge (part 2), the homophones were randomly selected. Then, the weakness presented in the first challenge is no longer there. Thus, in this case you need a generic algorithm for solving homophonic ciphers. However, note that it can be useful to know that each column of the table contains either 3 or 4 homophones. This makes the attack easier.

Any ideas for solving the third challenge are very welcome. It would be really good for the historians to decrypt this telegram.

Good luck by solving the challenges :)
Best regards
Luis

Re: Challenge  

  By: george4096 on March 31, 2014, 5:37 p.m.

Hi Luis

Many thanks for your exciting challenges and your kind clarifications.

In fact I already solved #2 by chance, partially manually.
I can tell you more on a private message. I want to develop this manual method into a programs.

I will definitively use your thesis idea to work on #2.

Regards
George

Re: Challenge  

  By: lbenthins on April 1, 2014, 10:43 a.m.

Hi George,

congrats, I am glad you solved challenge 2 !! I am really interested about how you did it. Could you please write me to my email ([HTML_REMOVED]Luis.BenthinSanguino@rub.de[HTML_REMOVED]) and tell me about your method?

Best regards
Luis

Re: Challenge  

  By: sir5 on May 6, 2021, 1:53 p.m.

quite a while [HTML_REMOVED] but can anyone check my solution, please? there is a little bit unknown, but when changing it, the remaining makes no sense … [HTML_REMOVED]

thx and greetz

Re: Challenge  

  By: tryone144 on May 7, 2021, 4:04 p.m.

Hi sir5,

you can send me a PM with your solution and I will take a look.


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