Provably fair unknown event time for Bitcoin gambling I have a bitcoin lottery that is still in the prototype stage (bitsplit.it).

I believe that the game will be much more appealing, for certain reasons, if players (and the house) both don't know when the next winner will be chosen.

However, I am having a hard time with coming up with a (feasible) way to prove that the house doesn't know when the pot will split.

Any ideas are greatly appreciated.
You could leverage the blockchain itself and use something based on the hash of the current block. For example, the block hash will end in a 0 bit roughly half the time. It will end in 00 bits roughly 25% of the time, etc. This is exactly the same idea as the bitcoin "difficulty" parameter, you would be using the hashes as a roughly constant rate stream of unpredictable random bits.

I think everybody who participates would agree that the block hashes are not predictable in advance.