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zkNode

zkNode is the software needed to run a zkEVM node. It is a client that network users require to synchronize and know the state of the Polygon zkEVM.

The main actors influencing the L2 State and its finality are the trusted Sequencer and trusted Aggregator.

The zkNode architecture is modular in nature. See the below diagram for more clarity.

zkNode Diagram

Most important to understand, is the primary path taken by transactions; from when users submit the transactions to the zkEVM network up until they are finalized and incorporated in the L1 State.

Polygon zkEVM achieves this by utilizing several actors. Here is a list of the most prominent zkEVM components;

  • The Users, who connect to the zkEVM network by means of an RPC node (e.g., MetaMask), submit their transactions to a database called Pool DB.
  • The Pool DB is the storage for transactions submitted by Users. These are kept in the pool waiting to be put in a batch by the Sequencer.
  • The Sequencer is a node responsible for fetching transactions from Pool DB, checking if the transactions are valid, then putting valid ones into a batch. The sequencer submits all batches to the L1 and then sequences the batches. By doing so, the sequenced batches should be included in the L1 State.
  • The Synchronizer is the component that updates the State DB by fetching data from Ethereum through Etherman.
  • The Etherman is a low-level component that implements methods for all interactions with the L1 network and smart contracts.
  • The State DB is a database for permanently storing state data (but not the Merkle trees).
  • The Aggregator is another node whose role is to produce proofs attesting to the integrity of the Sequencer's proposed state change. These proofs are zero-knowledge proofs (or ZK-proofs) and the Aggregator employs a cryptographic component called the Prover for this purpose.
  • The Prover is a complex cryptographic tool capable of producing ZK-proofs of hundreds of batches, and aggregating these into a single ZK-proof which is published as the validity proof.

Users can set up their own local zkNode by following this guide here, or a production zkNode as detailed here.