Cipher Clock

[Petertompkin]

Solved it now – I was on these lines (Harry has redacted my “order of what wasn’t allowed” in my first post – but as I say, just an elementary error in a spreadsheet and once solved it came straight out 🙂

[Madness]

@f6exb, look under “NOT ENOUGH SUFFERING”

[Madness]

@M_mystery, the point of the first addendum (yes, there will be more) is that the cipher can be broken up into
two stages. In the first stage, a text is encrypted with a cipher clock that has NO KEY. That means that the
outer ring has the unmixed alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ#+. The second stage is a simple substitution
that acts on the output of the first stage. The substitution uses 28 letters, however, so be careful.

The reason that this helps you is that it gives a hint on how to use the crib to crack the ciphertext. I won’t
say any more than that, because I wouldn’t want to deprive you of the joy of epiphany.

Good luck.

[Petertompkin]

Madness – I did in the end (just a matter of a Caesar shift) – but as I say, I had a blunder in a spreadsheet that meant it was looking up the wrong thing. I am still not certain why the crib was necessary!

[Harry]

Our tech support team have posted a report on keys for the cipher clock device. You should be able to find it at
https://2020.cipherchallenge.org/wp-content/uploads/2020/12/standards1.pdf

Hope it helps,

Harry

[Mattyrat2027]

Hi,

I have been working on 7B (haven’t we all ;D ), specifically working out a crib I think is correct, but I came across a slight issue. In ‘moving’ the hands of the cipher clock (I’m working on a paper diagram) I would like to ask if you have to work out how many degrees each hand moves. I was just counting how many letters the first hand moves, then applying my proposed gearing and counting how far the other hand should move.

Please could you tell me if my method would work?

Thank you and have a great Christmas.

[Madness]

To @mattyrat2027, who must be named after a video game, the hands each move the same number of characters, but each
hand counts its characters from its own ring around the circumference. So one takes 26 steps to go all the way
around, and the other takes 28 steps. But at all times both hands move the same number of steps. Hope that’s clear.

If you are mathematically inclined, look at the amendment to the report in the case files. It gives some algorithm
for dealing with the cipher clock.

And…, of course, the burnt piece of text might be a good crib. Just sayin’.

A very naughty elf told me that there might be a video of a working cipher clock coming out, but Harry hasn’t
decided if or how to post it.

[Bubba]

@Mattyrat2027 Your description is ok. You should not need to work out the angle turned (you *could* but why would you?) As you say, counting the number of letters (steps) the first hand moves and applying that number of steps to the other hand (with a different order and number of characters in its alphabet).

[C_brain]

@Mattyrat2027 on the clock cipher, the gearing is set up such that the number of letters advanced in both the inner and outer wheels is the same. So you don’t have to calculate any degrees, but you work out how many spaces the first hand moves and you do the same to the corresponding hand. The only complicating factor is for the inner wheel you subtract 26 and for the outer wheel you subtract 28 if it goes over. Hope this clears it up (I may not have understood your problem correctly)

[F6exb]

#52770:
Do we have to look at 3B ?

[Petertompkin]

The key point is that the hands move in a one-step-for-one-step way – you may find it helpful to think of them as two interlocked gear wheels instead, one with 26 teeth and one with 28 teeth

[Chik2008]

Hi Madness

Thanks for your help but I still haven’t cracked mission 7b. 😔 I still can’t find an effective way of decrypting the message. I am probably going to just call it quits and give up with the cipher clock. Please can somebody tell me how the crib is supposed to help me in this? Thanks everyone! 😊

[Mattyrat2027]

@Madness @C_brain @Bubba thank you for the messages, it was useful.

However, in response to #52758 I have encrypted the (burnt) crib with an unkeyed clock and then looked for patterns of which letters come where, and seeing if any letters echo that in the ciphertext I then would have gone on to substituting in the way I deem to be correct, but I worked through all 28 characters of the alphabet and found nothing. Is there a crucial step I am missing (you do not have to fully reveal what I have done wrong)?

Thanks

[Madness]

@chik2008 and @mattyrat2027, do not give up. Maybe Harry will release the notes on breaking the cipher clock with a crib.
The essence of it is to encrypt the crib with an unkeyed device (with an unmixed ciphertext alphabet), then see if there
is any place in the ciphertext where it would be possible to put that crib. At such a place, the difference between the
encrypted crib and the ciphertext should be a simple substitution cipher. So if it looks like A and B both map to C, then
you’re at the wrong place and have to put the crib somewhere else in the text. Once you find the right position, the key
to the substitution is the key for the cipher clock.

[Bubba]

@chik2008 and @mattyrat2027,if the crib-wrangling isn’t helping, remember that another weakness in this implementation has been identified. With the mis-matched alphabet lengths 26/28 it means that encryption (max steps = 26) cannot result in all cipher alphabet characters. There are 2 characters that cannot follow any given ciphertext character. One such character is the duplicate (i.e. there should be no double/repeat characters in the ciphertext). Also, importantly, the preceding character in the ciphertext alphabet cannot be the following character in the encrypted version of the message (without fractionation or similar). Frequency analysis of bi-grams is helpful.

[Author]

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