Provably Fair

How Commit-Reveal Works

Step-by-Step Verification Guide

1. 1

   Find your Round ID

   After placing a bet, the Round ID is shown in the Provably Fair sidebar on the CoinFlip page. You can also find it in the BetPlaced event emitted by your bet transaction.

2. 2

   Read the round data on BscScan

   0x3c4d853F...0B4a1F18

   Go to Read Contract → getRound(roundId) and enter your Round ID. Note these fields:

   • commitment — the locked hash
   • revealedSeed — the secret seed (visible after settlement)
   • player — your wallet address
   • betAmount — your bet in wei (18 decimals)
   • resultSide — 0 = Heads, 1 = Tails
3. 3

   Verify the commitment matches the seed

   Run in your browser console (with ethers.js v6) or any Solidity tool:

   // Verify commitment
   const { ethers } = require("ethers");
   const abiCoder = ethers.AbiCoder.defaultAbiCoder();
   
   const encoded = abiCoder.encode(
     ["bytes32", "uint256"],
     [revealedSeed, roundId]
   );
   const computedCommitment = ethers.keccak256(encoded);
   
   console.log("Stored commitment:", commitment);
   console.log("Computed commitment:", computedCommitment);
   console.log("Match:", commitment === computedCommitment);
   // Must be true!

4. 4

   Reproduce the result yourself

   Compute the result using the same formula as the smart contract:

   // Derive resultSide (same as Solidity contract)
   const packed = ethers.solidityPacked(
     ["bytes32", "uint256", "address", "uint256"],
     [revealedSeed, roundId, player, betAmount]
   );
   const hash = ethers.keccak256(packed);
   const computedResultSide = Number(BigInt(hash) % 2n);
   
   console.log("Computed resultSide:", computedResultSide);
   // 0 → Heads  |  1 → Tails
   console.log("On-chain resultSide:", resultSide);
   console.log("Match:", computedResultSide === resultSide);
   // Must be true!

   If both checks pass, the game was provably fair.

5. 5

   Verify the settler's signature (optional)

   The settler address is stored on-chain. Call settlerSigner() on the contract. Verify the signature from the BetPlaced transaction:

   // The settler signs: keccak256(abi.encode(commitment, roundId))
   const sigMessage = ethers.keccak256(
     abiCoder.encode(
       ["bytes32", "uint256"],
       [commitment, roundId]
     )
   );
   const recovered = ethers.verifyMessage(
     ethers.getBytes(sigMessage),
     signature
   );
   console.log("Recovered signer:", recovered);
   console.log("On-chain settlerSigner:", settlerSigner);
   console.log("Match:", recovered === settlerSigner);

Cryptographic Formulas

Security Model

Contract Address

Frequently Asked Questions