Provably fair is a cryptographic system that allows any player to independently verify that a game outcome was determined before the round started and was not manipulated by the casino. Duel uses server seeds, client seeds, and nonces — committed before play begins and revealed after — so every result can be audited. No trust in the casino is required.
A system in which game outcomes can be independently verified by players using cryptographic proofs. The casino commits to a hashed server seed before a round, the player provides a client seed, and the combined hash determines the outcome. After the round, the server seed is revealed, allowing verification that the hash was set before play.
Why Provably Fair Matters
Traditional online casinos use Random Number Generators (RNGs) that players cannot verify. You must trust the casino's RNG is fair. Regulators audit RNGs periodically, but between audits, players have no real-time way to confirm fairness.
Provably fair systems eliminate this trust requirement entirely. The mathematics of cryptographic hashing make it computationally impossible for either party to manipulate outcomes after the initial commitment.
How Duel's Provably Fair System Works
Server Seed Generation
Before any game round, Duel's server generates a random server seed — a long random string. This seed is immediately hashed using SHA-256 (a one-way cryptographic function) to create a server seed hash, which is committed to the player before the round begins.
Player Provides Client Seed
The player provides a client seed — either the default random one or a custom seed they choose. The client seed ensures that even if the server wanted to manipulate results, they couldn't know in advance what the player's seed would be.
Nonce Increments
A nonce (number used once) increments with each game round using the same seed pair. This creates unique outcomes for each individual round without requiring new seeds for every bet.
Outcome Determination
The game outcome is determined by combining the server seed, client seed, and nonce through a deterministic algorithm. The result maps to the game outcome (crash multiplier, mine positions, dice result, etc.).
Verification After Round
After you rotate or retire a seed pair, Duel reveals the original unhashed server seed. You can then verify: (a) SHA-256(server seed) = the committed hash; (b) combining server seed + client seed + nonce through the algorithm produces the observed game outcome. If both check out, the round was provably fair.
Why Manipulation is Impossible
The SHA-256 hash function has two critical properties that make manipulation impossible:
- One-way: Given SHA-256(server seed), it is computationally infeasible to determine what the server seed is. The casino cannot choose a hash that corresponds to a specific outcome they want.
- Deterministic: Given the server seed, client seed, and nonce, only one outcome is possible. There is no way to alter the outcome after the seeds are committed.
This means:
- Duel cannot change the server seed after committing the hash (the hash would no longer match)
- Duel cannot know the client seed in advance (you set it)
- The combination of both seeds creates a unique, unmanipulable outcome
How to Verify a Duel Game Result
- In your Duel account, navigate to your game history
- Select any completed round to view its seed information
- Note the server seed (now revealed), client seed, and nonce
- Verify: SHA-256(server seed) = the hash that was committed before the round
- Run the seeds through the game's outcome algorithm (documentation available on Duel) to confirm the result matches what you experienced
Provably Fair vs. Standard Casino Audits
| Feature | Duel Provably Fair | Traditional RNG Audit |
|---|---|---|
| Verification by player | Yes — any round | No |
| Real-time verification | Yes | No (periodic audits only) |
| Trust required | None — mathematically provable | Must trust casino + auditor |
| Manipulation possible | Computationally impossible | Theoretically possible between audits |
| Transparency | Full | Partial |