[EVM] Add get random source to Cadence Arch #5742
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ramtinms
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Apr 19, 2024
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| func RandomBeaconAddress(chainID flow.ChainID) flow.Address { | ||
| return systemcontracts.SystemContractsForChain(chainID).RandomBeaconHistory.Address | ||
| } | ||
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Does this have to be here, given we pass the chainID to the underlying layer. I know we do this for storage account but I think that's a legacy from the time EVM storage address was not part of system contracts.
ramtinms
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Apr 19, 2024
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| func(u uint64) (uint64, error) { | ||
| return rand, nil |
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I might add a line here to check if the input that is received is what is expected.
ramtinms
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Apr 19, 2024
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| uint64 output = abi.decode(data, (uint64)); | ||
| return output; |
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I usually use the verify methods to verify the output matches what is expected, for example see the verifyArchCallToFlowBlockHeight , we check the output produced matches the expected.
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I did that in Go test, but it makes sense to adpot the pattern you made
ramtinms
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Apr 19, 2024
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Closes: #5507
This PR implements a new function on the Cadence Arch precompile contract, that exposes access to Flow RandomBeaconHistory contract. This allows for retrieving a random source in the EVM which can be used as a seed for any PRG implementations.
The new method could be called like so:
It also allows for implementing commit-reveal schemes which are required for a lot of applications and was discussed on Discord: https://discord.com/channels/613813861610684416/1230199673629835375
We must keep in mind that the new function for obtaining random source relies on Cadence block heights not EVM block heights, which are not co-related but this is fine since we can use the get latest flow height function also available on Cadence arch.
@sisyphusSmiling even made a proof of concept that abstracts away this implementation detail https://gist.github.com/sisyphusSmiling/3e58dc3827c69afd038abe65ef8dda92