Provably Fair Mines, Plinko and Coinflip: Verify Your Own Game

Crash is one round shared by everyone, so it proves fairness with one public seed per round, covered in Provably Fair, Explained. Mines, Plinko and Coinflip against the house are different: each game is yours alone, so each player gets their own seeds. Here's how that works and how to check a game you played.

The three ingredients

• Server seed: a secret random value chosen by Solacrash. You see its SHA-256 hash before you play, which locks it in without revealing it.
• Client seed: a value you control. You can change it to anything you like at any time.
• Nonce: a counter that goes up by one with every game you play on the same seed pair, so each game gets a different result.

Every result, where the mines are, which way the ball bounces at each peg, which side the coin lands, is computed from those three values with HMAC-SHA256. Because the server seed was locked in by its hash before you chose your client seed and played, neither side can steer the outcome.

Why you can't check it straight away

If you could see the server seed while you played, you could compute your next Mines board before choosing tiles. So the server seed stays secret while you're using it. When you rotate your seed pair, Solacrash reveals the old server seed and starts a new one, and from that moment every game played on the old pair can be checked.

Verifying a game, step by step

1. Open the game and find the Provably fair panel under the board. Note the hashed server seed and your client seed.
2. Play as many games as you like. Each one uses the next nonce.
3. Press Save & rotate seed. The previous server seed is revealed.
4. Check that the SHA-256 hash of the revealed seed matches the hash you saw before playing. If it does, the seed wasn't changed.
5. Open the fairness page, enter the server seed, client seed and nonce of any game, and the verifier recomputes the board, drop or flip in your browser.

Coinflip duels work slightly differently

A duel is between two players, so neither should be able to decide it. The server seed for each duel is committed (its hash is shown) when the duel is created, and the joining player's browser adds its own random seed when they join. The result needs both, so neither the creator nor the house can choose it. Seeds are published once the duel settles. The Coinflip guide covers duels in full.

What provably fair does and doesn't promise

It proves the result was fixed before you played and computed the way the site says. It does not mean you'll win: the multipliers still carry the house edge, 1% on Mines and about 1% on Plinko. The Mines calculator and Plinko odds show exactly what that edge looks like for any setting.

Fair doesn't mean favourable. It means nobody, including us, can change the result after you bet.