Discussion thread for Add EIP: SLOT precompile by Marchhill · Pull Request #9141 · ethereum/EIPs · GitHub
This EIP proposes to add a new precompile that returns the corresponding slot for the current block.
It is currently possible to calculate the slot number from the block timestamp. However, this requires hardcoding the chain slot length into a smart contract. This would require the contract code to be changed in the event of a future change to slot length. A better approach is for the slot number to be calculated by the execution layer and exposed in a precompile.
This precompile aims to improve support for encrypted mempools. In order to be secure, the validity of encrypted mempool transactions should be tied to the inclusion of all transactions by a proposer in the correct slot. This rule can be enforced by a smart contract using this precompile.
2 Likes
Sharing a use case for this in support of the discussion: Verifying execution layer data with reference to the Beacon Chain requires calculating the Beacon Chain slot containing the execution layer block in its Execution Payload. The Beacon Chain provides the cryptographic primitives required to prove the inclusion of execution layer data in the canonical history of the chain but the first hurdle is matching an execution layer block to its Beacon Chain counterpart.
2 Likes
another option here would be to just compute the slot off-chain, pass it in to the smart contract in the calldata, and authenticate with EIP-4788
no new protocol functionality needed
Yes this is possible but much more expensive than using the precompile which costs 2 gas. I think it is more likely that people would end up using the hacky way (calculating from timestamp) rather than this more expensive way; ideally we want to make the right way cheap.
Another advantage of this EIP is that it exposes the slot number to the EL. In Nethermind we currently need the slot number for building Shutter blocks, it’s likely other clients will too in future. Rather than calculating from the timestamp in the EL, I think that the CL should serve as the source of truth for the slot number.
Overall this EIP is not making something new possible, but making something that is already possible cleaner and cheaper. It could also save us time down the line if we want to change the slot length.