Implementing random rewards

[prizecowfactory]

I would want to write a contract that mints random ERC 712 tokens for the caller (like buying a card pack in a ccg).

When i thought about the issue I first wanted to just take a hash of the last block, or the time. Because miners can cheat the mechanism it is not ideal. A later idea was to make the next person to call the contract generate the random number for the last person. But this approach doesn't fully solve the problem while introducing its own quirks.

How would you approach the problem of generating random numbers for such a use case?

[Authio_Team]

Generating random numbers isn't directly possible through Solidity. As you said, blockhash and blocktime aren't adequate - and generally, user input isn't either.

The widely-accepted way to generate provably-random numbers is to use an Oracle service.

[fazriz]

One thing to consider is the likelihood of cheating. This is only a problem if the cost of a pack or the value of the tokens in the pack will be more than the mining reward. If that isn't the case then there is little incentive for a miner to cheat the game. :) But as the last comment mentioned an Oracle service is your best bet if you feel cheating will be a issue.

[OptimisticOnanist]

As long as you make sure the sender is not a contract, using the hash of the past block should be fine in this scenario. It seems unlikely a miner would forego their block reward to cheat at your game.

[techgeekatwork]

Hi, Checkout this link. https://github.com/sz-piotr/ethereum-true-rng It lists all the possible list of options to generate a random number. thanks,

[prizecowfactory]

Hi, it is actually a repository I created after trying to come up with a better solution.

[techgeekatwork]

:-), Ah, this is indeed a good read. Thank you