medium10 pts · first answer countssmart-contract-security

Random winners on chain

A lottery picks a winner with uint256(keccak256(abi.encode(block.prevrandao, block.timestamp))) % players.length. What is the problem?

A.keccak256 output is not evenly spreadB.prevrandao is secret until the next epoch, so the result is safeC.The values are known or can be influenced before the transaction is final, so validators or contracts can predict or bias the result; use a VRF or commit-revealD.abi.encode cannot take block values

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