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Generally the procedure I follow with a cipher is:

Make a function to decrypt it, it should work every time

Find a value to use in hill climbing – for most ciphers this is tetragram fitness, sometimes you can use other values like IOC for vigenere to help.

Make a function to calculate the value – for fitness you need to download a corpus, record ngram frequencies and store the logarithm

Make the hill climbing script – iterate through digram, trigram and tetragram fitness making random swaps. Break the script when the key has reached a stable position.

Once you have one of these, the only thing that really changes between them is the decrypt function. Just try to work through it bit by bit until it works.

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