The Affine cipher is a monoalphabetic substitution cipher and it can be
the exact same as a standard Caesarian shift when
"a" is 1. Mathematically, it is represented as e(x) = (ax + b) mod
m. Decryption is a slightly different formula, d(x) =
a-1(x - b) mod m.
To encode something, you need to pick the "a" and it must be coprime with
the length of the alphabet. To make this easier, I have the (+) and (-)
buttons to change the A to the next higher or lower coprime number.
This is your encoded or decoded text: