A Technical Deep Dive into Polygon zkEVM

Polygon zkEVM aims for EVM-equivalence, not just EVM-compatibility. This means that most Ethereum applications, tools, and infrastructure can be seamlessly deployed on Polygon zkEVM without any modifications. Developers can migrate their smart contracts, dApps, and tooling directly onto zkEVM, ensuring that everything works as intended right from the start.

Why does this matter?

1. No Code Changes: You don’t need to tweak your existing Ethereum dApp, reducing the chance of introducing vulnerabilities.
    
2. No Extra Audits: Since the code remains unchanged, additional audits aren't needed, saving both time and resources.
    
3. Security Inheritance: zkEVM maintains Ethereum's robust security model, meaning it benefits from Ethereum's established security.

Polygon zkEVM uses a unique combination of cryptographic technologies to achieve its scalability:

1. Zero-Knowledge Proofs: The zkEVM system uses eSTARK proofs and FRI (Fast Reed-Solomon Interactive Oracle Proof of Proximity) to validate transactions off-chain. These proofs are compressed using FFLONK SNARKs, creating a final proof that’s much smaller and easier to verify.
    
2. Off-Chain Computation: Most of the heavy lifting is done off-chain, meaning only essential data and the final ZK proofs are submitted to Ethereum. This approach drastically reduces gas fees from about 5 million to just 350,000 wei.
    
3. zk-SNARK & zk-STARK: The system uses zk-STARKs (very fast but large proofs) for proving computations and zk-SNARKs (smaller but slower proofs) for attesting to the correctness of zk-STARK proofs. This blend ensures high speed without compromising security or efficiency. 

Polygon zkEVM is designed with rigorous security measures. Here’s how it maintains top-notch security:

1. Smart Contracts for Security: Smart contracts manage state changes and validity proofs, ensuring that all state transitions are accurately recorded and verified on-chain.
    
2. Timelock Mechanism: The zkEVM smart contracts include a 10-day timelock, allowing users to react and withdraw funds if any upgrade appears suspicious.
    
3. Multisig Governance: A multisig contract controls upgrades, requiring 2 out of 3 participants' approval for any changes. Additionally, in emergencies, an 8-participant Security Council with a 6/8 threshold can remove the timelock to protect user funds.

The zkEVM architecture consists of three main components:

1. The Trusted Sequencer: Ensuring Transaction Order and Execution

The Trusted Sequencer plays a critical role as the entry point for all Layer 2 (L2) transactions in the zkEVM ecosystem. It performs the following key functions:

• Transaction Reception: It receives L2 transactions directly from users, ensuring that the network processes them promptly.
   
• Batching and Ordering: After collecting the transactions, it orders and compiles them into blocks. These blocks are then grouped into batches, which represent a set of transactions meant for validation.
   
• Submitting to L1: The sequencer submits these batches to the consensus contract on Ethereum (Layer 1). This step ensures that the data is stored securely on-chain, maintaining transparency and auditability.

The sequencer's ability to interact with L1 helps maintain consistency and security between the two layers, providing users with an efficient and low-cost transaction environment. Additionally, the sequencer helps achieve near-instant transaction finality on the zkEVM chain by allowing transactions to be processed quickly before full L1 verification.
 

2. The Trusted Aggregator: Validating with Zero-Knowledge Proofs

The Trusted Aggregator serves as the zkEVM's verification engine. Its main job is to ensure that all transactions processed by the sequencer are valid and comply with the zkEVM's rules:

• ZK Proof Generation: The aggregator generates zero-knowledge proofs (ZK proofs) that confirm the correctness of the sequencer's transaction batches. These ZK proofs are cryptographic attestations that verify a transaction's integrity without revealing the details of the computation, ensuring both privacy and accuracy.
   
• Verification Process: Once the ZK proofs are generated, the aggregator submits them to the consensus contract on Ethereum. This process enables Ethereum to confirm that all L2 state changes are legitimate and trustworthy.
   
• Maintaining L2 State Integrity: The aggregator computes the L2 state based on the sequencer's batches and ensures that all state transitions are valid. It ensures that any changes to the zkEVM chain are consistent with the rules enforced by the underlying smart contracts.

By using zero-knowledge proofs, Polygon zkEVM achieves high scalability without sacrificing security, allowing it to handle a massive number of transactions while maintaining the integrity of every state change.
 

3. The Consensus Contract: The Backbone of Security and Verification

The Consensus Contract is a smart contract deployed on Ethereum that serves as the ultimate arbiter of the zkEVM’s state. Its primary functions include:

• Storing Transaction Sequences: The consensus contract records every transaction batch submitted by the sequencer. This step provides a reliable and transparent history of all transactions processed on the zkEVM network.
   
• ZK Proof Verification: When the aggregator submits a ZK proof, the consensus contract verifies its validity. This step ensures that every state change in the zkEVM chain aligns with Ethereum’s security guarantees.
   
• Maintaining State Transitions: It keeps track of L2 state changes and commits them once the ZK proofs are verified. This mechanism provides the zkEVM with a robust layer of security, as the consensus contract ensures that all state transitions are authenticated before they become part of the zkEVM chain.

By combining these three components—sequencer, aggregator, and consensus contract—Polygon zkEVM achieves an architecture that provides high throughput, scalability, and Ethereum-grade security while maintaining low transaction costs. This layered approach ensures that zkEVM remains efficient, secure, and transparent, setting a new standard for Layer 2 scaling solutions.
 

The zkEVM node is a versatile component that can operate in three distinct modes, each serving a specialized function:

1.Sequencer Mode:

• This mode is responsible for handling the Layer 2 (L2) state, which includes processing batches of transactions and managing the sequence in which they are executed.
   
• The sequencer takes incoming user transactions, validates them, and orders them into blocks. It then broadcasts these blocks to other L2 network nodes to ensure immediate finality.
   
• The sequencer interacts directly with Layer 1 (Ethereum) to ensure that all state changes are properly recorded, submitting transaction batches for further validation.
   
• It maintains a "pending transactions pool," which stores transactions that haven’t been executed yet, ensuring efficient processing even during high-traffic periods.
   

2.Aggregator Mode:

• In this mode, the zkEVM node focuses on verifying the integrity of transaction batches executed by the sequencer.
   
• The aggregator’s main task is to generate zero-knowledge proofs (ZK proofs) that validate the correctness of the transactions. It uses advanced cryptographic techniques to produce these proofs efficiently.
   
• The aggregator fetches batches from the consensus contract on Ethereum and verifies them off-chain before submitting the final ZK proofs back to Ethereum. This ensures that only valid state changes are committed to the blockchain, maintaining the system's security and integrity.
   

• The aggregator mode essentially acts as the bridge between L2 and L1, ensuring that every transaction processed on Polygon zkEVM is accurately represented and verified on Ethereum.
  
  

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3. RPC Mode (Remote Procedure Call):

• This mode serves as a relay between the L1 and L2 chains, maintaining an up-to-date instance of the L2 state by continuously synchronizing with the trusted sequencer and consensus contract on Ethereum.
   
• It doesn’t actively generate proofs or execute transactions but ensures that data from L1 is accurately relayed to L2. It also allows users and developers to query the L2 state, providing real-time access to the current blockchain state.
   
• The RPC node checks for synchronization updates every few seconds (default is every 2 seconds), ensuring that it stays aligned with the latest state transitions occurring on Ethereum.

By operating in these modes, Polygon zkEVM ensures a seamless flow of data and transactions between Ethereum (L1) and its Layer 2 network, providing scalability, efficiency, and high throughput without compromising security.
 

Polygon zkEVM isn’t just about scalability; it’s about preserving the developer and user experience:

• Gas Optimization: Through its ZK technology, it offers reduced gas fees compared to other Layer 2 solutions.
   
• No Compromise on Security: By inheriting Ethereum's security, zkEVM ensures that L2 transactions are as secure as Ethereum's mainnet transactions.
   
• Rapid Adoption: Its EVM-equivalence means that dApps, wallets, and tools built for Ethereum can immediately start working with zkEVM, accelerating mass adoption.

Connecting your wallet to Polygon zkEVM is easy:

1. Mainnet:
   • RPC URL: https://zkevm-rpc.com
   • Chain ID: 1101
   • Block Explorer: Polygon zkEVM Explorer
      
2. Cardona Testnet:
   • RPC URL: https://rpc.cardona.zkevm-rpc.com
   • Chain ID: 2442
   • Block Explorer: Cardona Testnet Explorer
      

Alternatively, you can use Chainlist to connect to the network in a single click.

1. Deploying dApps: Simply deploy your Ethereum smart contracts on zkEVM using the same tools like Remix, Truffle, or Hardhat.
    
2. Testing on Cardona zkEVM Testnet: Use the Cardona testnet to experiment with your dApp before going live.
    
3. Bridge Assets: Use the Polygon Portal to bridge assets from Ethereum to zkEVM and vice versa.
    

When building on Polygon zkEVM, it's crucial to prioritize security due to the complexity of the zero-knowledge proof mechanisms and interactions between L1 and L2 chains.

Here are some essential points to consider:

1. Smart Contract Auditing: Since zkEVM involves intricate interactions with L1, ensuring your smart contracts are secure is vital. Vulnerabilities in your contract can lead to significant losses or disruptions.
    
2. Transaction Verification: Ensure that off-chain computation and proof generation processes are tamper-proof, as any vulnerabilities here could compromise the entire system's integrity.
    
3. Bridging Security: Given the reliance on cross-chain communication, make sure that bridge components are fortified against potential exploits.
    

To mitigate these risks, always get your code audited by a reputable security firm like QuillAudits. You can also leverage their AI-powered agent, QuillShield, to detect and address vulnerabilities efficiently before deploying on the mainnet.