3.3 Substitution Cipher
With the Substitution Cipher for each character of the alphabet
another character must be spcified on which it is to be mapped.
To receive a bijection, every character must occur exactly once in the
cipher.
For instance, this corresponds to using the neighbour key
on a typewriter or keyboard.
source
The applet only shifts characters and numbers and leaves all other symbols
unchanged.
(Keys for testing:
SNVFRGHJOKLAZMPQWTDYIBECUX ,
LVXSWDFGUHJKNBIOPEARYCQZTM)
