Admin Role and Governance
The Admin is an Ethereum account that controls the Consensus contract, but it is planned to be removed in the future. It is the only account in the contract that can call the following functions;
setTrustedSequencersetForceBatchAllowedsetTrustedSequencerURLsetTrustedAggregatorsetTrustedAggregatorTimeoutsetPendingStateTimeoutsetMultiplierBatchFeesetVeryBatchTimeTargetsetAdmindeactivateEmergencyState
All ProxyAdmin.sol instances that can upgrade the contract implementations of the zkEVM Protocol belong to the Admin account.
Moreover, all proxies are owned by the Admin account, making it the only account authorized to make modifications to the contracts used to implement the zkEVM Protocol.
Timelock Controller
Timelock Controller is a smart contract that enables setting up a delay to provide users some time to leave before applying potentially risky maintenance procedures.
A timelock controller has been added to the zkEVM Protocol in order to improve user security and confidence.
An admin can schedule and commit maintenance operations transactions in L1 using a timelock controller, and the timelock can be activated to carry out the transactions when a specified minDelay time has passed.
The Polygon zkEVM team has decided to use the OpenZeppelin's TimelockController.sol contract to inherit security as well to avoid the lengthy and complicated audit process. We have changed the getMinDelay method in the contract and this modified implementation is named PolygonZkEVMTimelock.sol contract.
In the event that the zkEVM contract system is in Emergency Mode, the new getMinDelay will set the time minDelay to 0. The zKEVM Protocol’s Admin role is set to an instance of PolygonZkEVMTimelock.sol contract address during the deployment.
Governance of zKEVM Contracts
The Admin role requires significant responsibility and cannot be assigned solely to one account. For this reason, the Admin Ethereum account of a PolygonZkEVMTimelock.sol contract instance is assigned to a multisig contract that acts as a governance tool for the zkEVM Protocol, therefore decentralizing the management power among multiple trusted entities.
Below figure shows the governance tree of Polygon zkEVM L1 contracts.
Protocol maintenance operations can only be performed by following these steps:
Due to the governance chain among protocol contracts, any transaction on behalf of the Admin role can only be done through the below steps.
Maintenance operations transactions are proposed and stored into governance multisig contract. Polygon team reaches a consensus on whether or not to apply these operations. Voting inherits security from L1.
Once a decision has reached, if the results are favorable to perform maintenance operations, the governance multisig can be triggered to schedule the transactions to be executed once a time delay has passed using PolygonZkEVMTimelock.sol contract instance.
Once a time delay has passed, PolygonZkEVMTimelock.sol contract instance can be triggered to execute scheduled transactions and fulfil maintenance operations.