This is basically what I want to do with monero:
- Alice holds a contest and the winner will get some XMR as bonus.
- Alice deposits some XMR on blockchain and others can verify the existance of such bonus.
- After a winner is decided, he is given other information that enables him to get the bonus.
This can be quite easy using Ethereum and smart contract. But is it possible in Monero? At first I think Alice can just deposit bonus in a new Monero address. By revealing view key, people can confirm the existance of bonus. By sending the winner spend key, the winnier can spend it. But it seems there is no guarantee that Alice will give a winner the real spend key honestly. Also it cannot prevent Alice from spending the XMR in advance since she also knows the private key.