Provably fair
A system ("équitable et vérifiable") that lets you check with math that a result was locked in before you bet and never changed after.
Provably fair (équitable et vérifiable) is how crypto casinos show you an outcome was decided ahead of time and couldn't be tweaked once they saw your bet. It runs on three ingredients: the casino's secret server seed, a client seed you pick, and a bet counter called the nonce.
The short version
- Before you play, the casino locks in its secret server seed by showing you the seed's SHA-256 hash.
- You set your own client seed, which the casino can't guess.
- Every bet runs HMAC-SHA256 with the server seed as key, over a message made of your client seed plus the nonce. That output becomes your result.
- When you switch seeds, the casino reveals the old server seed. You hash it, make sure it matches what they showed you, then redo every result yourself.
What it proves, and what it doesn't
It proves that results from games you can verify line up with the seeds the casino committed to. That's it. The house edge stays the same, third-party slots and live dealer tables aren't covered, and it's no guarantee the site will actually pay you. Every casino sets it up a little differently, so check using that site's documented method.