Cipher Clock

[Teymour_aldridge]

When solving problems, I find it really helpful to think about what I currently know and what I’d like to work out.

Things currently known:
=> the crib
=> the ciphertext
=> the ciphertext is *probably* in English

Things to work out:
=> the plaintext

I suggest using the crib to solve the problem – of course you can do it without, but it might be easier with.

If you think about how the clock works can you match up the ciphertext to the position in the text it came from? [Let’s keep this interesting – edited by Harry]

Note that you do know the starting state of the little hand (first letter in the crib) [Edited by Harry]

Harry might (probably will) [did] edit this liberally – I promise that it started as an attempt to provide a hint, but degenerated to a full solution pretty quickly.

[Xmask]

[Sorry, Harry]

(digram frequency table)
It looks better in excel, with color. And sudoku on zeroes
this will possibly also be redacted i suppose.

something i’ve used for years now is conditional formatting, 2-color scale, white to blue (because it looks the nicest), shows patterns really nicely

[67105112104101114]

@Philthy, the trick is to think about what the cipher can and can’t do, like how a major weakness of Enigma was that it can’t encrypt a letter as itself. This cipher doesn’t have that weakness but it does have another probably more major weakness, based on the fact that there are 2 extra letters in the ciphertext (interestingly this weakness doesn’t work if there is only one extra character). The most notches we can rotate the hands at a time when encrypting is 26 which is going from a letter to itself, this means that [Edited by Harry, muhaha] is completely impossible and allows us to discount a lot of pairings from the key and eventually find the solution.

[Teymour_aldridge]

One possible conclusion is that Uncle Wilhelm is not involved.
[Possible, but not entirely true perhaps? Harry]

[Teymour_aldridge]

Ok, Uncle Wilhelm could be involved, but the letter might not be addressed as “Dear Uncle Wilhelm”

[F6exb]

@Teymour alridge
In #52632 I wanted to speak about this paper. And I think this made Madness laugh in 52573.

[Philthy]

@67105112104101114, Thanks, I now see how it’s done.

[Loujj97]

I’m trying to do it by hand but do I need a keyword?

[Petertompkin]

Made some progress (I think) but now wondering if I have made a fundamental error of understanding or just a mistake in the calculations. I’m not a computer programmer – just working with spreadsheets to do the donkey work – but (prior to Harry redacting almost all of this!) I have managed the following

1. Clearly if there are 28 letters on the cipher wheel then wherever you are, this makes it impossible for the next cipher letter to be the one before it; almost an Enigma-like weakness; perhaps not surprising as this appears to be in effect a one-rotor cipher with the prospect of a plugboard in the form of re-ordering the letters by substitution
2. This shows up in the bigrams – every cipher text letter cannot be followed by itself (would require 28 steps) which explains the lack or repeated letters in the cipher text, and by at least one other, which suggests the order [… Edited by Harry] but I think I may have an error here, since…
3. … using this key (or a circular permutation of it) – which matches the 28 keys of a previous contributor – to encipher the given crib produces the corresponding number of possible ciphertext fragments, but regrettably none seems to appear in the cipher text!

🙁

[Madness]

@Petertimpkin, why not try to decrypt with the 28 possibilities, rather than worry about the crib?

@Chik2008, the point is that the cipher can be split into two stages: one stage is like a cipher clock without a key
and the other is like a simple substitution.

@Everyone, someone please go look at “Not Enough Suffering” for a cribless challenge.

[M_mystery]

Hi everyone.My team, a group of first timers are really struggling on 7b. We have looked through all of the case files and we have found no help. None of us know how to program properly either. We found this https://2020.cipherchallenge.org/wp-content/uploads/2020/12/TECHNICAL-REPORT-1937-213A-addendum.pdf in the case files but we are y7 and have no clue of what it means. Is there any way to simplify technical report part 4? Thanks

[Petertompkin]

🙂 elementary error in spreadsheet!!

Cracked it now; made no use of the crib in the end, just relying on the identified fundamental weakness in the cipher.

[67105112104101114]

If Harry lets this through @Petertompkin, think about the ordering of what isn’t allowed

[18goyaan]

Well if its to Karl it starts Karl ‘e’. I thought maybe Karl evacuate but no. Karl escape? No. Why is this cipher punishing me!

[F6exb]

I can’t find the cryptograph cipher that Madness put on the Forum a few days ago. I need to check the original cipher text with my copy because in my plain text I have 5 sentences with garbage around them. Each of these sentences has about 80 letters.

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