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Challenge "Weakened Granit — Part 2"

Challenge "Weakened Granit — Part 2"  

  By: admin on Sept. 24, 2015, 7:34 a.m.

The challenges for the simplified GRANIT cipher, a method that can be done manually, serve as an exercise and use an intentionally simplified version of GRANIT.

Part 2 is a ciphertext-only challenge for which the first permutation key is known.
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 Last edited by: admin on Oct. 31, 2021, 2:55 a.m., edited 1 time in total.

Re: Challenge  

  By: Integral on Oct. 12, 2015, 12:07 p.m.

Hello,

In the description of the Granit encryption in the Granit-Part1 .PDF, you mention DCT and you specify on page 9 two conditions to be satisfied by KL1 and KL2 (lengths of R1 and R2):

  • KL1 <> KL2
  • KL1 >=15 and KL2 >= 15

These two conditions are weaker than the ones used in the standard DCT, where in addition one must have:
KL1 and KL2 are co-prime
KL1 and KL2 may not divide the length of the ciphertext

So my question is simply:
Are the 2 conditions specified on page 9 the only ones to be used in Granit, or should we add the 2 ones of the standard DCT ?

(my question stands for Weakened-Granit parts 2 and 3 as well as for Granit-Part1)

Thank you,
Integral

Re: Challenge  

  By: Scatha on Oct. 13, 2015, 12:22 a.m.

Hello Integral,

as I wrote in another post, I'll ask the author your questions. But there is one thing I can tell you right now:

On page 12 of the template for part 1 of Granit there is also stated that R2 is not allowed to have a full last row, which is equal to following rule:

  • KL2 may not divide the length of the ciphertext

If that rules should apply to KL1 also, and if KL1 and KL2 have to be coprime I will tell you as soon as I spoke to the author.

Best regards,
Scatha

Re: Challenge  

  By: Scatha on Oct. 13, 2015, 9:03 p.m.

Hello,

for the challenge series on the subject of GRANIT, please use only the rules given in the templates:

  • KL1 <> KL2 (part 1 page 9)
  • KL1 >=15 and KL2 >= 15 (part 1 page 9)
  • KL2 may not divide the length of the ciphertext (part 1 page 12)

These rules also apply for the weakened GRANIT, since the method is the same.

Thank you for your interest in these challenges. :)

Best regards,
Scatha

Re: Challenge  

  By: vexilla72 on Oct. 20, 2016, 7:11 a.m.

Hello,

For the challenges Weakened Granit Part 2 & 3, is the matrix found in the Part 1 the same one for the next challenges ?

Thanks you
vexilla72

Re: Challenge , solving methods  

  By: amateur on Oct. 17, 2017, 6:10 a.m.

Can we solve WG02 with only pencil, paper, n-gram stats and maybe a google search for R2 text?


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