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Puzzle Image

WMJS LX BN HCBMSQF MHXTAJJ UO GJNOQXURDYF HRB UHH HJPKJS PUT (UM) VTGTZFSE ZTSKV

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The ciphertext WMJS LX BN HCBMSQF MHXTAJJ UO GJNOQXURDYF HRB UHH HJPKJS PUT (UM) VTGTZFSE ZTSKV. decrypted reads:

THIS IS AN EXAMPLE MESSAGE TO DEMONSTRATE HOW THE CIPHER PRO (TM) SOFTWARE WORKS.

I found this by

Assuming it's a Vigenere cipher and performing Kasiski's examination on the ciphertext.

This tells us that the key is either 44, 22, 11, 4 or 2 characters long. If we assume 4 is the correct length, and then analyzing the letter frequency of each "row" (i.e. groups of letters that are 4 characters away from each other), we eventually arrive at the key dfba.

Edit: Turns out the only repeating substring has actually a distance of 43, not 44. So I basically found the solution by mistake :).


This of course is a very unsatisfying answer, and even with known plaintext & key I still don't know how to get the key from the image (assuming nothing else is hidden in the image!). I'll try again later, and maybe someone else figures it out faster with known key now.

By the way, "Cipher Pro (TM)" isn't a real software as far as I googled... Probably just a story-related fabricated name.
P.S.: Maybe another plaintext is hidden in the image? I somehow have the feeling the shown ciphertext isn't everything to solve...

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  • $\begingroup$ The image almost looks like morse code to me. Also it has 5s. $\endgroup$ – dcfyj Nov 3 '16 at 15:28
  • $\begingroup$ Seems right to me, but maybe he's hiding the REAL cipher in morse code. $\endgroup$ – hannah Nov 3 '16 at 15:32
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    $\begingroup$ To me, the image looks like black letters written in a blocky system font and then flood-filled with black from the outside, so that only the counters appear in white as in this example image. The S's are the inner part of a zero. B, D and 8 have unique shapes. A, P and R form a group, O and Q another. Most letters just vanish. $\endgroup$ – M Oehm Nov 3 '16 at 16:22
  • $\begingroup$ @CipherRiddle I'm honestly just too unmotivated to match all possible letters to the white shapes ATM. And considering the way you ask: No, I don't think I solved the entire cipher. $\endgroup$ – user14478 Nov 5 '16 at 14:18

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