Submission Details
Severity:
Anyone can predict the winner and pick himself.
Summary
The function selectWinner uses:
uint256(keccak256(abi.encodePacked(msg.sender, block.timestamp, block.difficulty))) % players.length;
to pick the winner , but all of these can be predicted and used to calculate a certain winner from the array.
Vulnerability Details
Never use block.timestamp, block.difficulty etc for a source of randomness.
Impact
High
Tools Used
Manual review
Recommendations
Use Chainlink VRF
Updates
Lead Judging Commences
Hamiltonite about 2 years ago
Submission Judgement Published Assigned finding tags:
weak-randomness
Root cause: bad RNG Impact: manipulate winner
Rewards breakdown
nSLOC
143This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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