Character frequency graph for cipher text I have studied about the mono-alphabetic substitution cipher. With Character frequency graph, the encrypted text can be decoded. I am wondering how can be happen?
In each language there is an expected distribution of characters so you can use this to make reasonable estimate as to characters.
For example, E is by far the most common letter in English words, followed by T, then A then O etc. So in your substitution ciphertext, the most common letter is probably E.
From pi.math.cornell.edu: