UA
RU
ENHow it works
- Before the bet, the casino generates a server seed and shows the player its hash, for example SHA-256. The seed cannot be worked out from the hash, and it cannot be swapped unnoticed: a different seed has a different hash.
- The player sets a client seed or takes the one issued. A bet number (nonce) is added to the seeds, and it goes up with every round.
- The outcome is calculated with a public formula from the two seeds and the bet number.
- Verification: when the player changes the seed pair, the casino reveals the old server seed. The player checks its hash against the published one and recalculates their rounds.
Round outcome = formula (server seed, client seed, bet number)For example, a player placed 1,000 bets on one seed pair and then changed the pair. The casino revealed the server seed, and all 1,000 outcomes can be recalculated and compared with the betting history.
In crash games the round is shared by everyone, so instead of one player's seed they use shared values that the casino cannot choose in advance.
Where it is used
It is used most often at casinos with crypto payments and in their in-house games: crash, dice, mines and similar fast games. Slots from major providers usually do not have it: there, fairness is confirmed by a lab certificate for the game and its RNG.
Provably fair vs certified RNG
| Provably fair | Certified RNG | |
|---|---|---|
| Who verifies | the player, any of their own rounds | an accredited lab |
| What it proves | the outcome was not swapped after the bet | the generator is random and RTP matches the declared figure |
| Limitation | does not show what RTP is built into the formula | the player cannot verify their own round |
The house edge is built into the formula that turns the seeds into an outcome, so RTP is checked separately. A hash check does not replace an RNG certificate if the licence requires one.
Common mistakes
- A hash, but no way to verify. Without a public formula and a verification tool, provably fair is just a marketing label.
- The player cannot change the seed. If the casino knows the client seed in advance, the server seed can be picked to match it. The player must set their own seed after seeing the hash.
- Promising more than is proven. The hash proves that the round was not swapped, but says nothing about the level of RTP. Do not claim that such a game is a better deal than a regular one.