Atbash is a simple substitution cipher possible with any known alphabet. It emerged around 500-600 BCE. It works by substituting the letters of an alphabet with another.
English alphabets in order is the constant.
CONSTANT = 'abcdefghijklmnopqrstuvwxyz'
A random shuffle of the constant is the ciper.
Example cipher: zyxwvutsrqponmlkjihgfedcba