That's what encrypted memos are for. You could have winner send email / contact to contact and deliver prizes. However probably easier to do the way you are doing it. Or maybe through NFTs. Think we'll have better tools for these types of things in time.
Hey thanks for replay, I have no clue what encrypted memos are, how do I encrypt the memo, can you show me where I can learn more about it? Thanks
Differences between a Memo and the Memo Key
The Memo key because it is a bit of an outlier. The only thing the Memo Key can do is encrypt and decrypt private messages that are sent through the blockchain. While this could one day be a powerful feature, today it is not commonly used. If you have received a private message that you would like to decrypt, as always you should use the key with the minimum necessary authorities, which in this case would be the Memo Key. source