Numbered array from 1...
* using 0 as starting point would immediately trigger one's "computer science" instinct, and then it's uncertain which bit is actually bit `0`? the least significant one (as is in most cases), or the most significant one?
* by using 1 as the starting point, I hope would induce most people to just use it as a counter to number things in the "normal" (for westerners) left-to-right top-to-bottom, thus encoding / decoding is more "natural";
I'd do it in my stash of hollerith cards, but I don't have a desk punch. I suppose I could simply take some of the pre-punched ones, and use them as the key phrase!