Fairness, Proven. Gambling Without the Nonsense.

How Duel's Provably Fair System Works

Provably fair is a cryptographic method that lets you confirm a casino never manipulated the outcome of a bet. Instead of trusting Duel's word, you can recalculate every result yourself. Every provably fair round on Duel is built from three ingredients:

• Server seed — a secret random string generated by Duel. Before you bet, you only see its SHA-256 hash, which commits the casino to a value it can no longer change.
• Client seed — a string from your own browser that you can edit. Because you control it, Duel cannot predict the combined result in advance.
• Nonce — a counter that goes up by one with every bet, so each round produces a unique outcome from the same seed pair.

These three values are combined with HMAC-SHA256 to produce a number that maps to your dice roll, crash point, mine layout, Plinko path or card order. Because the server seed was committed before the bet, the result is locked the moment you play.

Verify a Bet in 5 Steps

1. Note the hashed server seed shown before you bet.
2. Set (or note) your client seed and play your rounds.
3. Rotate your server seed — Duel then reveals the original, unhashed seed.
4. Check that the SHA-256 hash of the revealed seed matches the hash you saw earlier.
5. Enter the server seed, client seed and nonce into the verifier above (or any third-party tool) and confirm the output matches your in-game result.

If everything matches, the round was provably fair — proof that the outcome could not have been changed after you placed your bet.

Provably Fair Across Duel Originals

Every in-house game at Duel uses this system. Here is how it applies to each one:

• Duel Dice — the seed pair maps to a number from 0.00 to 99.99.
• Duel Crash — the seeds determine the exact crash multiplier.
• Duel Mines — the mine layout is locked before your first pick.
• Duel Plinko — every left and right bounce of the ball is fully deterministic.
• Duel Blackjack — the deck is shuffled with a seeded Fisher–Yates algorithm.

Why Provably Fair Matters

Ordinary online casinos ask you to trust a random number generator that a third party audits only from time to time. Provably fair turns that model around: fairness is public, permanent and checkable by anyone on every single bet. Combined with Duel's up to 0% house edge and 50% rakeback with code DUELFREE, it is one of the most transparent ways to gamble with crypto today.