What Is a Provably Fair Casino?

In a traditional online casino, you have to trust that game outcomes are fair. But how much is that trust justified? Provably fair technology solves this problem — it lets you mathematically verify game results yourself, eliminating the need for blind trust entirely.

How Provably Fair Works — Simple Version

Imagine you're making a bet with a friend on a coin flip. Your friend thinks of heads or tails in advance — but how do you know they won't change their answer after seeing yours? Provably fair is the solution: your friend seals their answer in an envelope before you guess. After the result, the envelope is opened. You can verify the answer was fixed before your guess.

Cryptographic provably fair works identically — the "sealed envelope" is a SHA-256 hash of the server seed.

The Dual-Seed System — Technical Detail

Duel Casino uses a dual-seed cryptographic system:

Server Seed

Before each round, Duel generates a random server seed. You're given a SHA-256 hash of this seed (not the seed itself). From a hash alone, it's computationally impossible to reverse-engineer the original seed — but after the round, you can verify the revealed seed produces the same hash.

Client Seed

You provide your own seed — the client seed — which influences the game outcome. You can change this at any time. This means even if Duel wanted to manipulate the outcome, your unknown client seed makes it impossible.

Nonce

Each bet has a sequential number (nonce). The combination of server seed + client seed + nonce determines the outcome through a deterministic algorithm.

Verification Process

After a round, the server seed is revealed. You can then:

• Confirm the revealed seed matches the previously shown hash
• Feed all three inputs into the same algorithm yourself and recalculate the outcome
• Confirm your calculated result matches what the game showed

Which Games Are Provably Fair at Duel?

All Duel Originals are provably fair:

• Dice — every roll verifiable
• Crash — where the multiplier crashes is predetermined and verifiable before the round ends
• Plinko — ball path is deterministic and verifiable
• Mines — mine positions are verifiable
• Keno — number draws verifiable
• Blackjack — card deals verifiable

Third-party slots (Pragmatic Play, Hacksaw, etc.) are not provably fair in this sense — they use RNG systems certified by independent auditors like eCOGRA or iTech Labs.

Provably Fair vs RNG Certified — The Difference

How to Verify a Duel Casino Game

• Play any Duel Originals game (Dice, Crash, Plinko, etc.)
• Go to your game history → find the round you want to verify
• Click the "Verify" button on that round
• You'll see the server seed, client seed, and nonce
• Use Duel's verification page or any SHA-256 HMAC calculator to recalculate the result yourself