I've researched commit reveal schemes, but am not sure the following is possible...
User mints a playing card. The number of card is hidden. At anytime, the user can choose to reveal the card number. (up until this point, the user does not know the card number). If the card number == 7, they win a significant payout.
My instinct is that the user can choose when to reveal and thus can control the outcome.
Most commit reveal schemes involve a period of time when all commits are made and a winning lottery number is chosen. I don't think this would work for the above situation.
Am I missing something?