AffineCipher decryption function value.

[ericbalawejder]

In the AffineCipher README.md, it states the value of y is the numeric value of an encrypted letter, ie. y = E(x). Should y = x, where x is the letter's index from 0 - length of alphabet - 1, in the decryption function?

The README.md states:

the decryption function is:

D(y) = a^-1(y - b) mod m

• where y is the numeric value of an encrypted letter, ie. y = E(x)
• it is important to note that a^-1 is the modular multiplicative inverse of a mod m
• the modular multiplicative inverse of a only exists if a and m are coprime.

If you let y = E(x), I believe this just shows that D(y) is the inverse of E(x).

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[sanderploegsma]

I'm pretty sure this was fixed in the problem-specifications, since it now uses i instead of x in the encryption function. See #2370.