Provably Fair means the outcome of every round is committed to before you bet, by math you can check yourself — not by “trust us”.
The server generates a secret seed and publishes its SHA-256 hash before any round uses it. You set your own client seed. Every bet consumes an incrementing nonce.
When the server seed is revealed — after rotation — you can check the hash matches what was published, then recompute the outcome with the same HMAC-SHA256 construction and the same rejection sampling. If it does not match, something is very wrong and you should contact us immediately.
Ruble originals use this end to end — blackjack, baccarat, roulette, dice, mines, keno, dragon towers and slots. Provider games and the sportsbook settle under their provider’s rules, not this scheme.