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Breaking the Mono-alphabetic Substitution Cipher

We are able to break the shift cipher because of it's small key space. In general, we learnt that the large key space is necesary for secrecy. However, we will now see that large key space is not always sufficient either.

About the experiment:

In this experiment, we work with another well-known historical encryption scheme, namely the mono-alphabetic substitution cipher, that has a very large key space. However, it is quite easily broken using "Frequency analysis" methods. Your task is to break this cipher. Specifically, given (only) the ciphertext in some instance of a mono alphabetic substitution cipher, you need to find the plaintext and the secret key.