Crack the Code

16 Sep 2021
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United Kingdom
Anyone into cracking codes?
For instance, if I write: "3,18,1,3,11-20,8,5-3,15,4,5"
That's a very simple one, and it replaced the letters of the alphabet with the corresponding numbers of the letters. Thus "crack-the-code"
I suggest keeping it relatively easy by only using well known phrases or sayings.
As usual the winner gets to go next. A relatively easy one to start:

As a clue, that's a mono-alphabetic substitution cipher.
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Too short, really.
By inspection I guess it's
"best foot forward" but I stopped looking after that, there could be other possibilities.

Trouble is with these things, one can dream up a method for which someone else would need some huge multiplier of the time it took to code in the first place, to solve.
And if the target text is too short, it's insoluble. The algorithm becomes as individual as a cipher, you just have to know it.

That's why I've never played a computer game!
Correct. Well done!
And I would also agree with your observation. The more complex the cipher, the longer it takes to solve. Also, as you say, the more text there is the better the chance of finding a key.
That was why I kept it relatively simple with a well known phrase and a simple cipher.
Straight substitution is to use a 26 lettter cipher, you're saying?
I didn't find a cipher or key!
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Straight substitution is to use a 26 lettter cipher, you're saying?
I didn't find a cipher or key!
Hmm, I'm not sure if we're talking about different things or at cross purposes.
The cipher is whatever process is used to turn the sentence into a code. As you've cracked it, you obviously found that I simply used the letter that occurs two letters later in the alphabet. But yes, it was a straight substitution. But you could use any alphabet, or numbers, and you could use a multi-layered substitution.
I didn't provide a 'key'. that's the whole idea, you have to find the key, then apply that key to the rest of the sentence to de-cipher it.
The easiest way to find a key is to look for a distinctive pattern of letters, such as the double 'q' in the middle word.
A double letter can only be a double 'e' or a double 'o'. That is why, for the first one, it was intentionally easy:
A well know saying with ????, 'oo' or 'ee', ???????
OK,, Ciphers aren't quite what I thought. Ta.
No, I didn't find anything. I just looked at it, nothing written.
As you say, central double letters. I assumed the substitution string was a jumbled alphabet.

EE led to things like
...t meet me.....
and no bells ringing.
t seemed a likely terminator.

OO led to
...t #oot #o.....
with all the rest different.

boot - - - - ...t boot bo..... - nah

foot - - - - - ...t foot fo.......

I since tried it with a couple of online codebreakers. None of them got it!

If you used some unforgettable number like 9265358979323846 (from Pi) and selected each number offset forward for even numbers and behind for odds, I'd never solve it.