Well, there is something we can try ^^

To be as most random possible, maybe we can check on Bitcoin ^^

Check a block, we can consider :

- number of transaction

- nonce

- size (bytes)

- total spend

- total fees

As example the block 873 240

So with consideration:

- number of transaction = 2477 = 2+4+7+7 = 20

- nonce = 3,616,984,066 = 3+6+1+6+9+8+4+0+6+6 = 49

- size (bytes) = 386,053,475 = 3+8+6+0+5+3+4+7+5 = 41

- total spend = 8 144 = 8+1+4+4 = 17

- total fees = 0.09

So the formula can be something like: (tx + nonce + size + spend) / fees

In that scenario : (20 + 49 + 41 +17) / 0.09 = 1411

1411 will be the number to found.

For example, you can say We are on the block 873 240, Let's go bet the result of the block 873 340, it's 100 blocks forward, around 16 hours later from now, you have 14 hours to bet from now.

And because your message is timestamped on nostr, we can verify you post the message before the block 873 340, by that we can be sure there is no cheat possible by you.

And you can't use someone to cheat, because of course we can check the reply timestamp.

So there is 100% guarantee of the legit lottery here 😉

Maybe something like that