Provably Fair: A Definition
One of the differences between your traditional online casino and one that accepts bitcoin is how they’re tested for fairness.
Non-bitcoin casinos are tested by companies like Technical Systems Testing. They run tests on the casino’s random number generator to see just how random the results are. So long as the games’ results are 100% random, they’re 100% fair.
What the heck does provably fair mean? Google gives us a few definitions:
1) Provably fair means the player can prove the operator didn’t cheat.
2) Provably fair means the shuffle and order of the cards are verifiably random and also that they can’t be changed once the game has started.
3) Provably fair means you know exactly what you are dealing with before you start. Game payout odds are clearly displayed in the payout table.
The bottom line – you can use a string of numbers (called a hash) to ensure the casino is dealing you a fair game.
Need An Example?
Here’s an example of how a provably fair game works.
Say, for example, I give you a tough math problem to solve. I state that I already solved it.
But you’re not so sure. So you have me write the answer down, compute its hash and give you the hash value. The solution is (still) a secret.
When you come up with the answer yourself, you can hash it and compare it to the hash I gave you. If the two hashes match, you know I wasn’t lying. I had the answer all along.
Does that make sense? To explain this in another (more technical and realistic) way:
A hash function is created using a (very strong, all but unbreakable) SHA256 algorithm. The purpose of this function is to take data (the cards that will be dealt) and turn it into a string called a hash. The point of the SHA256 system is to:
- Easily create hash values for any message.
- Make it infeasible to generate a message with any given hash.
- Make it infeasible to modify a message without changing the hash.
- Make it infeasible to find two different messages with the same hash.
The first hash (SHA) is called the Initial Deck. It’s like when the dealer starts to shuffle a deck of cards before the start of a hand, but before they have you cut it.
Then there’s the Player Seed. This is populated with a random string of letters and numbers generated by your browser.
What’s unique about the Player Seed is that you can edit it. You can enter anything you want here:
Enter it into the Player Seed field. Then hit deal, spin or play. The Player Seed will shuffle the deck again.
When the hand is over you’ll be shown the Initial Deck, Dealer Seed and Final Deck. You can verify the legitimacy of the hand by taking the Initial Deck and Dealer Seed, converting them to a hash, and making sure they match the SHA (Initial Deck). Then shuffle that with the Player Seed and your final result should match the Final Deck.
If you’re a visual learner like I am, that might confuse you. So the next best thing you can do is head over to Coin Royale, bitZino or SatoshiBet, and play their games and/or use their calculators. You’ll get to see how it works in real time.
Each site does this in a slightly different way. So you understand the basics work and know how to run a test. That way you can test sites before you sign up.
But I want to be very clear – just because a casino is ‘provably fair’ doesn’t mean it’s a legit and safe casino to join. It’s possible for a casino to deal you fair games, but then cheat you out of your money. For example, they don’t have to pay you your winnings. So bear in mind that testing for provably fairness is only one piece of the puzzle. It won’t replace common sense or doing your due diligence.
Want To Learn More?
Here are some links to websites that further explain provably fairness and have calculators for you to play with.
 You can use this page to verify the hashes for different casinos. http://bitcoincasinopro.com/provably-fair-verification/
 This is a list of verified provably fair sites. https://bitcointalk.org/index.php?topic=481137.0