This select the type of cipher used to encrypt the data. The
first choice is "Caesar". This is a simple cipher where each
character is shifted some number of characters within the
alphabet. See !!!! for additional information. You get to
specify how far each character is shifted. The next choice is
"Substitution". This is where each character of the alphabet is
mapped onto another character within the alphabet. In both cases
you can choose to have multiple keys. If you have (for example)
three keys, than the first one is used for the first character
of the puzzle, the second for the second letter, etc. Once you
run out of keys, the first one is used again. This makes the
first challange of cipher constructed in this way to find out
how many keys are in use, and then figuring out what the
patterns are.