Hi
We launched a new community dice game, Social Dice, at
https://betking.io a couple weeks ago and it was pointed out by RHarver that it wasn't actually provably fair.
He kindly said we could use the same method he uses at Bustabit to ensure our multiplayer game is provably fair. We only changed it a little.
You can read more about it in his thread
https://bitcointalk.org/index.php?topic=922898.0It works like so:
1) We generated a chain of 5 million sha512 hashes starting with a server seed that we randomly generated. So we take the sha512 of our server seed and then we take the sha512 of this hash and so on 5 million times.
The sha512 of the final hash is:
A86FE6011E456DDEF66FCAD16A16EA063746A718D7542B5C50C362D1D9792F4C458E4C71DD8F87D
F5F8BB4679304671AC9B1E60FC089F4CA745437AEB897646F
Posting it here means we can't pick a different chain in the future.
2) The final hash will be the hash of the first server seed used to generate a roll in the Social Dice game. We will then use the previous hash in the chain for the next round and keep playing through these hashes in reverse order.
3) So far we have only generated a chain of server seeds and that could allow us to choose a chain that favours a certain outcome so to make sure we can't do that we also add a client seed that we don't have any control over. The client seed will be the block hash of a Bitcoin block that is not yet mined, block 420731.
This server seed and client seed are fed into the exact same roll calculation method that the regular dice game uses.
I will update the provably fair help page on BetKing to detail this change and give code you can use to verify your results.
Thanks again to RHarver for giving permission to use and to Dooglus, Eric and Steve for their work developing the method which is detailed here
https://bitcointalk.org/index.php?topic=709185.msg8528454#msg8528454Quoted.
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