Provably Fair Crash Verifier (HMAC-SHA256)

Provably fair hash verifier

SHA-256 of server seed (compare with the pre-round hash)

4a05c8488ceda7f58944da860f399b7a868944aacc16db1068097f582332d9c2

HMAC-SHA256 (key = server seed, message = client:nonce)

c3de1dff4b69246ddfa98d67d6a9c0609baa340b66ed2f64b7347c0ff5cb9b18

Derived crash point

4.21x

Algorithms differ by game and provider. The generic mode shows the standard method; it will only match a casino's result when that casino uses the same formula.

How verification works

Before a round, the game shows you a hash of its secret server seed. This commits the game to the seed without revealing it.
You (or your browser) supply a client seed, and each round has a nonce counter.
After the round, the game reveals the server seed. You check that its SHA-256 hash matches the commitment, then recompute the result.

The generic method

In generic mode we compute HMAC-SHA256 with the server seed as the key and client_seed:nonce as the message. We take the first 52 bits of the result as a number U between 0 and 1, then apply the standard crash formula with the house edge you enter.

We add a provider preset only when the provider publishes its algorithm and we have checked it against real rounds. Read more in Provably Fair Explained.

Frequently asked questions

Why doesn't my result match the casino?

Each game uses its own formula: different message formats, hash functions, house-edge handling or seed chains. Our generic mode shows the common HMAC-SHA256 method. It matches only games that use that exact method.

Is it safe to paste my seeds here?

Yes. Everything runs in your browser with the Web Crypto API and nothing is sent to our servers. Only paste server seeds that have already been revealed, which means the rounds are over.