hard20 pts · first answer countssmart-contract-securitycryptography

Commit-reveal that can be copied

In a sealed-bid game, players commit keccak256(abi.encode(choice, salt)) and reveal later. An attacker copies a winner's commit hash and reveals the same values after seeing them in the mempool. What is the fix?

A.Use sha256 instead of keccak256B.Make the salt shorterC.Allow reveals only from EOAsD.Include msg.sender (and the contract and round) in the committed hash, so a copied commitment cannot be revealed by anyone else

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