New (Provably Fair) Experimental Blockchain Game

[Cyphase]

My OTC Rating

I'm running a new game as an experiment. If it works out I might turn it into a regular thing. Here's how it works.

I'll generate an address, a secret number between 0 and 0.01 (rounded to 8 decimal places so that it could be a valid amount of bitcoins), and a pseudo-random 256-bit nonce to use as salt. I'll post the address and the hash of a string of the form "<secret>|<nonce_hex>" (for provable fairness). You enter by sending some number of bitcoins to the address that I post. The winner is the person who sends the amount closest to the secret number.

Here's an example round of the game.

I would generate the following:

Address: 1Lcd4bmrSytyDzHYdz7pyx11vrswcERM5k
Secret: 0.00423374
Nonce/Salt: f0f93fee6b5f1ff588369e99eda3b310bc46eb47ea3e9a36702a7bdff1ae0224
Hashed Secret: SHA256("0.00423374|f0f93fee6b5f1ff588369e99eda3b310bc46eb47ea3e9a36702a7bdff1ae0224") == 4ca7bee7e2c6962c73d6dd7f9e841c80b7bf8f279d5b7fc37f72723c2858a0c6

I would then post the address and the hashed secret, and people could start sending in entries. Once the round is over, I would determine the winner and send the bitcoins to the address that sent the winning entry, after taking my cut. I would of course also publish the secret number and nonce as proof of fairness.

When is the round over?

I'll specify a block in the future; your transaction must be in this block or earlier. The block will be ~144 blocks from the current block at time of posting; at a rate of 6 blocks per hour, that works out to about 24 hours to send entries. Take into account that it's possible for your transaction to not make it into the next block generated after you broadcast it. Any late entries will be forfeited at my discretion.

How do you determine the winner?

The winner is the person who sends the amount closest to the secret number. If there are entries the same distance above and below the secret number, the greater amount wins. If there are multiple entries of the same amount, the one in the earliest block wins. If there's more than one in the same block, the winner is the sending address which, when hashed with the nonce in the form "<address>|<nonce>", yields the lowest hash value. And if multiple addresses hash to the same value, I'll waive my fee, they'll split the pot and we'll be on all the tech news websites for finding a SHA256 collision .

What's your cut?

For this first round I'll take 5% (or less if I'm convinced that's too much); let me know what you think about that percentage. I'll also guarantee that the winner(s) will get back at least what they put in, in case of a situation where they otherwise wouldn't. In fact, I'll likely keep that guarantee in place if I run this game in the future.

Good Luck!


Round 1

Address: 15STJxuU5gwTbNyPZXTqXgdph1KSfdpgR9
Hashed Secret: 9aa3d28b342c12fba4b38e0b499ce46dc8d498369ac0abc42affd6860f3579a3
Final Block: 230192

[Cyphase]

Well, no one has sent anything, so I guess I'll just extend the game another 144 blocks. Block 230336 will now be the last block. I'll also waive my fee for this round.

[Matthew N. Wright]

"Provably fair" seems to be missing from your thread.

[Cyphase]

I assume you mean from the thread title, because I do mention it in the post. Thanks for pointing that out.

[Matthew N. Wright]

I assume you mean from the thread title, because I do mention it in the post. Thanks for pointing that out.

Yep! Now you might get some attention! 

[Cyphase]

I might post this again in the "Games and rounds" sub-forum.