Your response is puzzling.  I directly answered your question and no I'm not on drugs.  The alphabet string can't be anything.  The alphabet is required to 1) know what shift value to assign each character of the shifting key and 2) what value to assign each character of the input string.  From there it is a bunch of addition operations modulo 62, and using that value as the index into the same alphabet to get the output.  You need some natural ordering of the characters in order to go from characters to numbers and then back to characters.  The 0=0A=10BABYA=36' clue was simply telling you the correct ordering to use. Get it now?  The clue has no other meaning than that. (And yes, I read the post. ) Glad I can help clear that up for you.