Provably fair verifier

How provably fair works

Before you bet, the casino picks a secret server seed and shows you only its SHA-256 hash. You pick (or accept) a client seed. Every bet uses a nonce, a counter that starts at 0 or 1 and goes up by one per bet. Because the hash is published first, the casino cannot change the server seed after seeing your bets, and because you choose the client seed, it cannot pre-compute results that hurt you.

When you rotate to a new seed pair, the old server seed is revealed. Hash it yourself: if SHA-256(server seed) equals the hash you were shown, the seed is genuine and every result made with it can be recomputed.

From seeds to a random number

This verifier uses the scheme Stake documents for its originals. It computes HMAC-SHA256 with the server seed as key and the message clientSeed:nonce:round. That produces 32 bytes. Each group of 4 bytes becomes one float between 0 and 1:

• float = b0/256 + b1/256² + b2/256³ + b3/256⁴
• One HMAC gives 8 floats. Games that need more (Plinko rows, Mines tiles) increase the round number to 1, 2… and hash again.
• Floats are used in order, so the same seeds and nonce always give the same result.

Game formulas used here

Dice: roll = floor(float × 10001) / 100, giving 0.00 to 100.00. Limbo: max(1, floor(1e8 / (float × 1e8) × 0.99 × 100) / 100), which gives a 1% house edge because the chance of reaching multiplier x is 0.99 / x. Plinko: each row uses one float; floor(float × 2) is 0 for left and 1 for right, and the landing slot is the number of rights. Mines: tiles 0–24 are drawn one by one, each float picking index floor(float × remaining tiles) from what is left; the first picks are the mines.

The crash-style option uses a generic per-bet formula, max(1, floor(99 / (1 − float)) / 100). Stake's multiplayer Crash and Slide do not use your client seed; they come from a pre-generated hash chain salted with a public value, so they need a different checker.

What verification proves, and what it does not

A matching result proves the outcome was fixed by seeds the casino committed to before your bet. It does not prove the payout table or house edge are what you expect, and it cannot cover games that are not provably fair, such as third-party slots and live tables. Check results in batches after rotating your seed, and keep the client seed one you set yourself.