The affine cipher is a type of monoalphabetic substitution cipher where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that each letter encrypts to one other letter, and back again, meaning the affine cipher is essentially a standard substitution cipher with a formula governing which letter goes to which. The cipher has the weaknesses of all substitution ciphers. Each letter is encrypted with the function (ax + b) mod 26, where b is the magnitude of the shift.
Use the above affine cipher decoder and encoder to encrypt/decrypt simple messages.