Each player picks a digit 0 through 9 when they buy their ticket. Publish each player's number alongside their entry.
Doesn't sound like it would be too hard to implement, also when a player buys a ticket that number is locked in, I can't pick that number. If someone has ticket #5 I can't also buy ticket #5.
Note that the digit they pick can be different than the ticket number.
"I'm buying ticket #5 and my 'lucky digit' is 8. The idea is that you as site operator don't know which 'lucky digit' each player is going to pick, so you can't predict in advance which ticket will win. The result depends on the individual choice made by every player.
The problem is that the
last player decides who wins - and if he also knows the 64 digit secret he can probably chose a 'lucky digit' such that he himself wins.