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Cool paper+pencil crypto problems each from a diffent type of cipher.
The specs are HERE
For each cipher students will either be asked to CRACK something or simple DECODE something.
If it says Cryptanalysis that means crack without the key.
Decoding simply means to go through the process of decrypting with the key.
Participants are given a resource sheet like this (varies year to year)
The most important skill to work on for this is a particular flavor of substitution cipher, the aristocrat...
We made a cool online tool for training and getting fast at these:
AWESOME ARISTOCRAT PRACTICE SITE
The mechanical parts:
This cipher is steganographic, that is, hiding in plain sight. We pick some feature to allow us to distinguish As from Bs.
In a codebusters test the difficulty of this problem is going to be how many possible As and Bs might be picked up on.
So in the following example there are a few possible candidates for As and Bs:
So just start decoding for one of the candidates and see if it is consistent and makes sense.
This one got cute.