How does BitLotto do it ?
All tickets are at one address. You can see them at blockexplorer.com. There is no way for me to trick how big the jackpot is. (you only need to look at DEPOSITS not the total. Some was taken out for payment of winner and some to refund overpayment of tickets. But add up the .25 tickets and the 1 BTC minus .75 refund and you'll get jackpot size)
Their payment hash is their ticket. I can't alter or fake that.