What is provably fair?
Provably fair means the house commits to a result’s inputs before you bet and lets you recompute it afterwards. You see the SHA-256 hash of a secret server seed before play, and a seed swapped after your bet would no longer match that hash.
That is the whole provably fair meaning: a result you can check, not one tilted your way. Provably fair gambling still carries a house edge, and Dice keeps its theoretical RTP of 97% either way.
How provably fair crypto casino games work
Knowing how provably fair crypto casino games work comes down to one loop: commit, bet, reveal, recompute. The same provably fair system runs every round under three rulesets.
Server seed hash, client seed and nonce
The server seed is 64 random hex characters, shown only as its SHA-256 hash until the pair rotates. The client seed is yours to set or change, and the nonce counts bets on the current pair, so each bet draws a fresh result. Rotating a pair that holds a bet reveals the old server seed and promotes the next hashed one.
The provably fair algorithm: HMAC-SHA256
The provably fair algorithm for Limbo, Plinko, Roulette, Reels, Mines and Chicken is HMAC-SHA256, keyed with the server seed over your client seed, nonce and round number. Each 4 bytes of output become one float between 0 and 1. Real-money Dice has its own ruleset: the first 32-bit word below the largest multiple of ten thousand that fits, modulo ten thousand, is the roll, so no roll is favoured.
Crash: hash chain and salt
Crash uses a hash chain instead of a seed pair: each hash is the SHA-256 of the next, and the final hash is committed before the first round. Each crash point comes from HMAC-SHA256 of the round hash with a salt fixed before play, so neither the chain nor the salt can be changed once rounds start. Crash keeps a theoretical RTP of 95%.
Provably fair bitcoin games and the inputs each needs
All the provably fair games in the lobby can be checked above if the extra settings match the ones you used. They work as provably fair bitcoin games because a BTC deposit converts to a dollar balance you move into your casino balance, and the coin never touches a result. Mines and Chicken place every mine or car from one nonce.
| Game | Inputs | How the result is read |
|---|
| Dice (real money) | Server seed, client seed, nonce | First accepted 32-bit word, modulo ten thousand, gives the roll |
| Limbo | Server seed, client seed, nonce | 97 divided by one float, rounded down, gives the multiplier in hundredths, never below 1x |
| Roulette | Server seed, client seed, nonce | One float times 37, rounded down, gives the pocket from 0 to 36 on a single-zero wheel |
| Plinko | Seeds, nonce, rows (8 to 16), risk (low, medium, high) | One float per row; the ball goes right on one half or more, and the number of rights picks the bucket |
| Mines | Seeds, nonce, mine count (1 to 24) | One float per mine, placed among the tiles still free on the 25-tile grid |
| Chicken | Seeds, nonce, cars (1, 3, 5 or 10) | One float per car, placed among the lanes still free from 1 to 20 |
| Reels | Server seed, client seed, nonce | Floats 1 to 3 stop the 32-stop strips, float 4 decides the respin, then one float per free cell for up to 12 respins |
| Crash | Round hash, salt | First 52 bits of HMAC-SHA256 set the crash point, capped at one million times |
How to use the provably fair checker
The provably fair checker above has two modes, Seed-pair games and Saved Dice bet, while Crash takes a round hash and salt. For a saved real-money Dice bet, the provably fair verifier compares the copied record with the revealed seed. If a result differs, recheck the game, nonce and settings, and never paste a wallet recovery phrase.
- Save the hashed server seed and set your client seed before play.
- Play, then rotate the seed pair to reveal the server seed.
- Choose Seed-pair games and your game, or the real-money Dice option.
- Paste the server seed, client seed, nonce, game settings and saved hash.
- Press Calculate and compare the result and seed hash with your records.
What provably fair verification proves
Provably fair verification proves that a result was calculated from seeds committed before your bet. It does not prove a bet was accepted or paid, and no laboratory certifies the scheme. Before winnings leave your casino balance, their bets are re-checked against this record once a seed pair holding settled bets is rotated; the bitcoin casino lobby covers the rest.