Fairness
OPDuel Originals
Limbo
Plinko
Keno
Roulette
Mines
Blackjack
Roll
Dice
Provably Fair for OPDuel Originals
Provably fair is the system OPDuel uses to generate outcomes for all Original games. It guarantees that game results have not been tampered with and that your bets are completely fair with the odds and outcomes as advertised.
With this system, the outcome is determined before you place your bet - meaning there's no way to manipulate results based on bet amount or any other factors.
How It Works
The logic behind each game uses publicly visible algorithms with three key elements: server seed, client seed, and nonce.
- Client Seed - A string you can set yourself at any time, giving you control over the fairness
- Server Seed - Generated by the server and shown to you as a hash. The unhashed version is revealed when you rotate your seeds
- Nonce - A counter starting at 0 that increases by 1 for each bet you make with that seed pair
These three values are combined using HMAC-SHA256 cryptographic hashing to produce deterministic random outcomes. The same inputs always produce the same result.
Manage Your Seeds
Our Games
OPDuel offers 7 provably fair original games:| Game | Description |
|---|---|
| Dice | Roll 0.00-100.00, bet over or under your target |
| Keno | 10 numbers drawn from a pool of 40 |
| Mines | Avoid hidden mines on a grid to increase your multiplier |
| Plinko | Ball drops through pegs, landing in multiplier buckets |
| Limbo | Instant crash-style game with 96% RTP |
| Roulette | European roulette with numbers 0-36 |
| Roll | 15-cell wheel with 2x, 7x, and 14x multipliers |
How to Verify Your Bets
Access the Fairness Checker by clicking the "Provably Fair" button in the bottom right corner of any Original game. This opens the verification menu where you can check any bet.
To verify a recent bet:
- While playing any Original game, select the "My Bets" tab at the bottom of the page
- Click on the bet you want to verify
- The verification details will show the seeds and calculation used
To verify older bets:
- Go to your Bet History
- Find and select the bet you want to verify
- View the provably fair breakdown for that bet
Need help finding a bet? Our 24/7 live chat support can help you locate any bet in your history.
The Algorithm
All OPDuel Originals use the same cryptographic foundation:
// Message format: clientSeed:nonce:round
hash = HMAC-SHA256(serverSeed, "clientSeed:nonce:round")
// Extract 4 bytes to create a random float between 0 and 1
float = byte[0]/256 + byte[1]/256² + byte[2]/256³ + byte[3]/256⁴Each game then applies its own formula to convert this float into a game result. See individual game pages for specific algorithms.
Multiplayer Games
Roll uses a different system for fairness since it's a multiplayer game. Instead of individual client seeds, Roll uses EOS blockchain block IDs as a public source of randomness. The block ID and a server secret are combined to determine the outcome, which can be verified after each round.
