What Does "Provably Fair" Mean?
Provably fair means you don't have to trust the casino. Every game outcome is generated using cryptographic functions (HMAC-SHA256) with inputs that both the server and the player control. The result is mathematically predetermined before you play — and you can verify it after.
Traditional online casinos use proprietary RNG (Random Number Generators) audited by third parties. You trust the auditor. With provably fair, you trust the math — because you can do the verification yourself.
How Roulette Uses Provably Fair
The winning number is a single integer 0–36, derived from HMAC-SHA256(server_seed, client_seed:nonce). The first 4 bytes are converted to uint32, then modulo 37 gives the result. Uniform distribution across all 37 pockets is verified mathematically.
Verification Process
- 1
Before each round, the server commits to a seed by showing you its SHA-256 hash. This hash is your proof that the seed existed before you played.
- 2
You provide your own client seed (or use the default). Combined with a nonce (incrementing counter), these three values determine the winning number.
- 3
When you spin, the result is computed as: HMAC-SHA256(server_seed, client_seed:nonce). The winning number is a single integer 0–36, derived from HMAC-SHA256(server_seed, client_seed:nonce). The first 4 bytes are converted to uint32, then modulo 37 gives the result. Uniform distribution across all 37 pockets is verified mathematically.
- 4
After rotating your server seed, the raw seed is revealed. You can now recompute every past result and verify they match what was shown to you.
- 5
Visit Rookie's Fairness page to paste any server seed, client seed, and nonce to independently verify results.
The Three Seeds
- Server Seed — Generated by Rookie. Its SHA-256 hash is shown to you before each round. The raw seed is revealed when you rotate to a new seed.
- Client Seed — Set by you. You can change it at any time. This ensures Rookie can't predict the combined output because it includes your input.
- Nonce — An incrementing counter that changes with each round. Prevents the same server + client seed combination from producing identical results.
FAQ
Is Roulette rigged?
No. The provably fair system makes rigging mathematically impossible without detection. If Rookie changed the server seed after commitment, the hash wouldn't match — and you'd see it immediately.
Can I verify old results?
Yes. After rotating your server seed, you can verify every round played with that seed. The nonce tells you which round it was.
How is this different from regular online casinos?
Regular casinos use opaque RNG systems audited by third parties. You trust the auditor. With provably fair, the cryptographic proof is available to anyone — no trust required.