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 Lights Out Uses Provably Fair
The entire elimination order is a Fisher-Yates shuffle of all tile indices, seeded by HMAC-SHA256(server_seed, client_seed:nonce). The shuffle determines the exact order tiles go dark — but they're revealed one at a time. You can verify the full order after rotating seeds.
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 elimination order.
- 3
When you play, the result is computed as: HMAC-SHA256(server_seed, client_seed:nonce). The entire elimination order is a Fisher-Yates shuffle of all tile indices, seeded by HMAC-SHA256(server_seed, client_seed:nonce). The shuffle determines the exact order tiles go dark — but they're revealed one at a time. You can verify the full order after rotating seeds.
- 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 Lights Out 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.