You guys could point me a better option though.. The idea behind this game is to select a winner (or more) from a list of particpants. The game would announce something like: "we are at block 568903 - result at 569000 (using nonces as seeds from block 568996 to 569000)"
Using multiple blocks would avoid nonces comming from only a miner, right?
This was
answered above I'm not sure whether including multiple nonces would up the security level that much (ie. since an attacker would know the other nonces, they could adjust their nonce-"space" accordingly).
The miner of block 569000 (in your example) could mine trying to use a nonce that results in an outcome in its favor.
If you published the hash of the
block numbers, plus extra "random text" you could avoid this attack vector because only you will know which blocks will be used until you disclose the result. You must include the additional text otherwise someone could brute force the block numbers.