`block.timestamp` and `block.prevrandao` has unexpected behavior on other chains decreasing the randomness.
Description
All chains do not have the same behavior for variable used in this protocol:
block.timestamp can be 23 hours in the past and 1 hour in the future on Arbitrum, tampering the end of the event.
block.prevrandao is always equal to 2500000000000000 on zkSync decreasing the randomness.
Risk
Likelyhood: Medium/Low
Sequencer can be in the past or the future on Arbitrum.
block.prevrandaois always equal to2500000000000000.
Impact: High
People won't be able to finish the event at the right time on Arbitrum and can miss the time to retrieve the funds.
Bad randomness on ZkSync
Recommended Mitigation
Do not use Arbitrum for protocol who need one specific day to use a function.
Use an oracle for randomness on ZkSync.
Lead Judging Commences
Weak randomness in `ChoosingRam::selectRamIfNotSelected`
The organizer is trusted, but the function `ChoosingRam::selectRamIfNotSelected` uses a way to generate a random number that is not completely random.
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