zkEVM Chain serves as an exceptionally efficient, deterministic, and decentralized distributed state machine. This blockchain meticulously records transactions in a sequence of interconnected blocks, with each block cryptographically anchoring to its predecessors along the same chain. This inherent feature renders any attempt to alter a transaction within a specific block futile without compromising the cryptographic integrity of subsequent blocks. As a result, blockchain transactions enjoy immutability and a high level of security.
The responsibility of upholding the blockchain's integrity falls upon block producers, who operate nodes responsible for both creating and validating blocks. These producers are elected by zkEVM holders, with each producer running an instance of a zkEVM node via the nodes service. Consequently, block producers currently engaged in the active schedule of block production are often referred to as "active" or "producing" nodes.
The Imperative for Consensus
In the context of distributed nodes, block validation poses a formidable challenge. To ensure the fault-tolerant validation of blocks within the decentralized framework, a consensus model becomes a necessity. Consensus serves as the mechanism by which distributed nodes and users collectively agree on the current state of the blockchain, fostering trust and reliability within the system.
zkEVM Chain Consensus
Proof-of-Efficiency (PoE) is a two-step model that divides tasks between Sequencers and Aggregators in the zkEVM Chain. Sequencers collect L2 transactions and create L1 transactions to propose batches. These batches serve as data availability for the L2 network. Sequencers pay L1 gas fees and a deposit in $zkEVM tokens to propose batches.
Aggregators, on the other hand, participate in the Proof-of-Efficiency consensus protocol. They create validity proofs for new L2 states by being the first to do so. Batches proposed by Sequencers in L1 are sorted, and the first valid validity proof that updates to a new state is accepted by the PoE smart contract. Aggregators must define their objectives and strategy for proof generation. Late aggregators incur costs, but gas fees are mostly recoverable.
Fees are distributed as follows:
L2 TX fees go to the Aggregator creating the validity proofs.
All TX fees go to the corresponding Sequencer of each batch.
Deposited fees from Sequencers for batch creation go to the Aggregator including the batch in a validity proof.
This mechanism ensures decentralization, minimizes potential attacks, and encourages participation by multiple parties in the zkEVM Chain.