Provably Fair Explained
How cryptographic verification proves casino game results are legitimate. No trust required — just math.
What is Provably Fair?
A cryptographic system that lets you verify casino game results weren't manipulated after you bet. The casino commits to an outcome before the round starts — you can check that commitment after the round ends.
If the math checks out, the result was fair. If it doesn't, the casino cheated. No auditor needed. No trust needed. Just cryptography.
How Seeds Work
Three components determine every result:
- Server seed — generated by the casino before your bet. You see a SHA-256 hash of it upfront. After the round, the actual seed is revealed. You verify the hash matches.
- Client seed — you set this yourself. It's mixed into the result calculation, so the casino can't predict the outcome alone.
- Nonce — a counter that increments with each bet. Ensures each round produces a different result even with the same seeds.
The result is computed as: HMAC-SHA256(server_seed, client_seed:nonce) — this hash is converted into the game result (a number, a card, a multiplier, etc.) using the game's specific algorithm.
The Verification Process
- Before betting: casino shows you the server seed hash (commitment)
- You set your client seed (or use the default)
- You place bets — nonce increments each round
- When ready to verify: rotate your server seed (this reveals the previous one)
- Take the revealed server seed + your client seed + nonce
- Compute HMAC-SHA256 yourself
- Convert the hash to a game result using the game's algorithm
- Compare to what the casino showed you
If they match: the result was determined by the committed seed. The casino couldn't have changed it after seeing your bet. The hash commitment locks them in before you play.
Which Games Support It?
On Rainbet: Dice, Limbo, Hilo, Keno, Tower, Blackjack, RPS, Plinko, Wheel, and Chicken Cross. Stake uses the same HMAC-SHA256 algorithm — the WITS.GG verifier supports Stake's format for compatible games.
Not all casino games are provably fair. Table games with live dealers, slots from third-party providers (Pragmatic, NetEnt, etc.) — these use RNG certified by testing labs, not provably fair cryptography. The distinction matters: certified RNG means an auditor checked the system. Provably fair means you can check every individual round yourself.
Verify on WITS.GG
The WITS.GG verifier runs 100% in your browser. Seeds never leave your device. Enter your server seed, client seed, and nonce — the verifier computes the result and compares it to what the casino showed.
Supports single-round verification and multi-round scan — verify 100+ rounds at once to check an entire session. If any round doesn't match, you'll know exactly which one.