Affine

Similar to a Caesarian shift, but also adds in a multiplier to further scramble letters.

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) \bmod m. Decryption is a slightly different formula, d(x) = a^{-1} (x - b) \bmod m.

To encode something, you need to pick the a and it must be coprime with the length of the alphabet, which is the m value. To make this easier, I have the (+) and (-) buttons to change the A to the next higher or lower coprime number.