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Challenge "Weakened Handycipher — Part 1"

Challenge "Weakened Handycipher — Part 1"  

  By: admin on May 12, 2015, 10:32 p.m.

The challenges for the weakened Handycipher serve as an exercise and use an intentionally weakened version of Handycipher. Part 1 is a partially-known-plaintext challenge with a helping additional information.

Handycipher is a newly designed cipher to permit pen-and-paper encrypting and decrypting, while providing a significantly high level of security.
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 Last edited by: admin on Oct. 31, 2021, 2:55 a.m., edited 2 times in total.

Re: Challenge  

  By: bgr on May 19, 2015, 4:55 p.m.

Hello,
I understood that the core cipher consists of the 31-character alphabet (A-Z and in addition the strings ,.-?^). This 31-character alphabet is enhanced by the digits from 0 to 9, then a permutation of these 41 characters generates a secret key. The secret key has the length 41, too.
Afterwards these 41 characters are displayed as a 5x8 matrix. The character '^' was surpressed (hopefully this is the right word). Then a 31-character subkey is generated from the shared key by deleting the digits 0-9 again, which is used to create a substitution table. Suddenly the '^' is in again (same position as in the secret key).

My question:
Was the character '^' surpressed only in this example, or is it always the '^'?

Bernhard

Re: Challenge  

  By: curmudgeon on May 19, 2015, 10:51 p.m.

The 40 non-space characters of K are always displayed as a 5 x 8 table, T-subK.
The 31-plaintext-character subkey P is always derived from K by omitting the decimal digits.
Therefore the table never contains the space, but the subkey always contains the space. (I.e., not just in this example.)

Hope this helps. [HTML_REMOVED]

Re: Challenge  

  By: bgr on May 20, 2015, 1:14 p.m.

Thank you for the explanation. I completely misunderstood one expression in the document.

As it was written "The 40 non-space characters of K …", and the example for K was "O N 2 T P 3 F L …", I thought that the spaces between the single characters are meant and I was wondering why they explained this.
Thanks!

Bernhard

Re: Challenge  

  By: günter on March 6, 2016, 10:22 p.m.

This is probably a fairly stupid question, but I need help counting the dogs. [HTML_REMOVED]

The solution shall consist of ten names, but I find eleven! There are three dogs mentioned in the known part of the plain text, and there are eight more once the remaining text is decrypted.

Well, one of the dogs gets renamed… so am I supposed to drop the old name, and only use the new name?

Re: Challenge  

  By: curmudgeon on March 7, 2016, 12:05 a.m.

…Well, one of the dogs gets renamed… so am I supposed to drop the old name, and only use the new name?

Yes, just so.

Re: Challenge  

  By: günter on March 7, 2016, 5:24 a.m.

Works! [HTML_REMOVED] Thank you!

Re: Challenge  

  By: Greko on May 17, 2016, 10:59 a.m.

I believe I have found the plaintext and the names of the dogs but my solution is not accepted. Would it be possible any of the solvers or a mtc3 team member to verify my solution?

Also it is not mentioned in the challenge pdf if we have to enter the solution in capital letters or in a different format (for example only the first letter to be capital).

Thank you,
Greko

Re: Challenge  

  By: Scatha on May 17, 2016, 3:51 p.m.

Hello Greko,

I'll give you an example for how to enter the solution.

If the names you found would be John,Harrison,Martha, and Jane, you would have to enter them like this:

John,Harrison,Martha,Jane

Please try to enter your solution again. If it doesn't work, feel free to contact me with your solution and we'll try to figure out why.

Best regards,

Scatha

Re: Challenge  

  By: Veselovský on Feb. 22, 2019, 3 a.m.

If I count the dogs correctly, then plaintext speaks about 9 different dogs. Two of the dogs have two different names. So there are 11 different names. One of the names consist of three words. Some of the names are mentioned several times. Names appear both in know plaintext and unknown plaintext. Should be names from known plaintext also be included in solution? What is point of doing so, if we already know them without any decryption?

So if I read "The solution consists of the names of the ten dogs mentioned in M7. Please enter the names in the order in which they appear in the text, separated by commas." it tells me nothing what solution to submit.

Re: Challenge  

  By: AnLeRo on Feb. 22, 2019, 3:59 p.m.

If I count the dogs correctly, then plaintext speaks about 9 different dogs. Two of the dogs have two different names. So there are 11 different names. One of the names consist of three words. Some of the names are mentioned several times. Names appear both in know plaintext and unknown plaintext. Should be names from known plaintext also be included in solution? What is point of doing so, if we already know them without any decryption?

So if I read "The solution consists of the names of the ten dogs mentioned in M7. Please enter the names in the order in which they appear in the text, separated by commas." it tells me nothing what solution to submit.

The known plaintext is part of the whole plaintext M7 and all ten names of the whole plaintext should be included. If names appear more than once, the first appearance is important for the solution.

Please send me a PM if you want me to check your solution. Maybe I can give you a hint for the tenth dog.


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