Provably fair is a system where a casino proves — using math, not promises — that every game outcome is genuinely random and was not manipulated. Instead of trusting the casino, players can independently verify each result using cryptographic tools. The "provably" part means it is mathematically provable, not just claimed.

Before you place a bet, the casino generates the game result and creates a cryptographic hash of it (called a "commitment"). This hash is like a sealed envelope — it locks the result in place without revealing it. After you bet and the game plays out, the casino reveals the original data. You can then hash it yourself and check that it matches the commitment. If it matches, the result was predetermined and fair. This is called a commitment-reveal scheme, and it is mathematically impossible for the casino to change the result after committing to it.

Most provably fair systems (including AlgoRoll) use HMAC-SHA256 — a cryptographic hash function that combines a server seed and client seed to produce a deterministic result. The server seed is committed before the game, and the client seed adds player-side randomness. Neither party can control the outcome alone. SHA-256 is the same algorithm that secures Bitcoin and is considered computationally unbreakable with current technology.

A provably fair system on a traditional server still requires you to trust that the commitment was actually made before your bet. Blockchain eliminates this by recording the commitment on a public, immutable ledger with a timestamp. AlgoRoll commits game results to the Algorand blockchain — you can see the commitment transaction on-chain before any bets are placed. This removes the last element of trust from the equation.

After any game on AlgoRoll, go to the Provably Fair page. Enter your game's server seed, client seed, and nonce. The verification tool recalculates the result using HMAC-SHA256. If the calculated result matches your actual game outcome, the result was fair. AlgoRoll provides code examples in JavaScript, Python, and CLI so you can verify using your own tools, not just ours.