Affine Cipher

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.

a: -

b:

This is your encoded or decoded text:

The postage stamp was first issued in England in 1840. Tyler Akins! <>
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