10B

[Olive-Tree3]

Hi Mrs-Robot,

I understand what you mean by the message you sent above; however, how does this relate to the cypher? I would be very grateful for another hint, thank you.

[Mrs-Robot]

Hi Olive-Tree3,

Think of the 3 needles and that night’s divisors.
If you analyse the text in that way, what stays the same, and what stays different?

[Olive-Tree3]

OH OHOHOHOH
OH
I SEE IT!! I UNDERSTAND IT!!
Thank you so much mrs robot, that was very helpful!!
It will take a lot of time of rearranging tho… wish I could write python

You can get a long way rearranging text using a text processor (like BBEDIT on a Mac) and/or a spreadsheet. Harry

[NoeSC]

Thanks Harry for such a brutal cipher ! thats some hours i’m never getting back. Happy we got it in the end tho.

[Japaninja]

Thanks for the challenge, Harry!

We got 10b down to what we believe to be an ADFGVX cipher (painfully quickly) but did not manage to crack it from there. Now the challenge is over can you tell us what we missed?

Thanks again.

Well done on spotting that! The key weakness in the cipher was the use of the 3-needle code to encipher the letters ADFGX. You really only need two of the needles as any two determine the third. In a sense that was a strength in that it disguised any variation in the frequencies, but once you have worked out that it is a 3-needle code it is a big weakness, as the needle distribution really helps to narrow the possibilities for the length of the transposition keyword, and, as outlined in the hints published in the news over the last week or so of the challenge, it also helps to work out which transposition has been used! Hope to see you back next year! Harry

[Author]

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