The Polygon Chain Development Kit (CDK) is an open-source framework designed to accelerate the deployment of ZK-powered Layer 2 (L2) blockchains on Ethereum. By enabling developers to launch customizable, scalable, and compliant app-specific chains, Polygon CDK is redefining how projects scale and innovate within the Ethereum ecosystem. This article explores its architecture, core advantages, data availability model, deployment differences between zkEVM and Validium, key node components, smart contracts, and overall data flow.
Why Choose Polygon CDK?
Polygon CDK is built with a developer-first philosophy, offering a modular and flexible foundation for building sovereign rollups. Its design principles prioritize scalability, customization, security, and interoperability—making it ideal for enterprises, Web3 startups, and decentralized applications requiring tailored blockchain solutions.
Core Design Principles
- Highly Modular Architecture: Developers can customize every layer—from execution environments to gas tokens—enabling full control over chain parameters.
- Scalability: CDK-based L2s significantly increase transaction throughput by leveraging zero-knowledge (ZK) proofs and off-chain data processing.
- Unified Liquidity: Chains built with CDK are natively integrated into the Polygon 2.0 ecosystem, ensuring seamless asset transfers and shared liquidity across L2s.
- Independent Data Availability (DA): Each chain benefits from dedicated Data Availability Committees (DACs), enhancing reliability and access to off-chain data.
- Composability & Interoperability: Powered by the LXLY Bridge, CDK chains enable frictionless cross-chain communication and asset swaps.
- Near-Instant Finality: Transactions achieve final confirmation quickly through cryptographic guarantees, eliminating the need for full nodes to validate every detail.
Key Advantages of CDK Chains
- Ethereum Scalability: CDK extends Ethereum’s capacity without compromising on security or decentralization.
- Custom Business Logic: Full EVM compatibility allows developers to modify gas limits, opcodes, and integrate custom tooling.
- Privacy Options: Supports private app chains where sensitive application data remains confidential while still benefiting from blockchain immutability.
- Regulatory Compliance: Enables network sovereignty—operators can select compliant validators and governance models aligned with regional laws.
- Extensive Web3 Support: As a direct fork of the zkEVM stack, CDK simplifies migration and leverages an established developer ecosystem.
👉 Discover how you can deploy your own ZK-powered chain in minutes
Understanding Polygon CDK Data Availability
Data availability (DA) is a critical component in scaling blockchains. It separates transaction execution from data storage—allowing data to reside off-chain while remaining verifiable. This approach dramatically improves scalability and reduces costs.
What Is Polygon CDK Validium?
Polygon CDK Validium is a unique scaling solution built on zkEVM technology that integrates a Data Availability Committee (DAC). Unlike traditional rollups that post all data on-chain, Validium stores transaction data off-chain but secures it through a trusted committee.
The DAC consists of independent nodes responsible for storing and verifying L2 batch data. Even if the sequencer goes offline, users can reconstruct the chain state using data preserved by DAC members.
How DAC Works
- The sequencer collects L2 transactions into batches and signs them using an ECC private key.
- Signed batch data is sent to DAC members via secure APIs.
Each DAC node:
- Validates the sequencer's signature
- Stores the off-chain data
- Signs the accumulated input hash once confirmed
- These signatures are returned to the sequencer, which submits only the hash to Ethereum L1.
This process ensures data integrity and availability without bloating Layer 1 with full transaction data.
Benefits of DAC
- Lower Transaction Fees: Reduced on-chain footprint means lower gas costs.
- State Privacy: Sensitive data stays off-chain while maintaining cryptographic proof of validity.
- Enhanced Security: Multi-signature thresholds prevent single-point failures.
Smart contracts on L1 manage DAC membership and signature verification, ensuring transparency and trust minimization.
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zkEVM vs. Validium: Deployment Differences
While both zkEVM and Validium use zero-knowledge proofs for state validation, their deployment architectures differ significantly in data handling and cost-efficiency.
zkEVM Deployment
zkEVM Node: Manages the network, processes transactions, and maintains state.
- Components: JSON RPC, Pool DB, Sequencer, State DB, Aggregator, Prover
- Repository: github.com/0xPolygonHermez/zkevm-node
zkEVM Contracts: Deployed on Ethereum
- Main Contracts:
PolygonZkEVM,PolygonZkEVMBridge,PolygonZkEVMGlobalExitRoot - Repository: github.com/0xPolygonHermez/zkevm-contracts
- Main Contracts:
Validium Deployment
Data Availability Layer
- Repository: github.com/0xPolygon/cdk-data-availability
zkEVM Node with Validium Extensions
- Repository: github.com/0xPolygon/cdk-validium-node
Validium-Specific Contracts
CDKDataCommittee.sol: Manages DAC members and verifies signaturesCDKValidium.sol: Handles state updates and batch finalization- Repository: github.com/0xPolygon/cdk-validium-contracts
Comparison Summary
| Feature | zkEVM | Validium |
|---|
(Note: Table removed per instructions)
Instead:
Transaction Data Storage
In zkEVM, all transaction data is posted directly to Ethereum L1. In contrast, Validium only submits a hash of the batch data to L1, keeping full data off-chain under DAC custody.
Data Availability
zkEVM offers full on-chain DA—maximizing decentralization. Validium relies on DAC for off-chain availability, trading some decentralization for lower fees and higher throughput.
Security Model
zkEVM’s security stems from complete on-chain data availability and ZKP verification. Validium remains secure due to ZK proofs but introduces trust assumptions around DAC members potentially colluding—mitigated by multi-signature thresholds.
Gas Efficiency
Validium significantly reduces gas costs since less data is written to L1. This makes it ideal for high-frequency applications like gaming or payments.
Final Settlement
Both require ZKP submission to L1 for finality. However, Validium adds a preliminary step where DAC signatures must first validate the batch hash before proof generation.
Key Components of zkEVM Node
Understanding the internal structure of the zkEVM node is essential for developers deploying or maintaining a CDK-based chain.
- Aggregator: Submits aggregated ZK proofs to L1 after collecting individual proofs from provers.
- Prover: Generates zero-knowledge proofs for transaction batches to verify correctness.
- Sequencer: Orders transactions, executes state transitions, and provides initial finality.
- SequenceSender: Sends batch fingerprints (hashes) to L1 and coordinates with DA layers.
- Synchronizer: Keeps L2 node state in sync with Ethereum by listening to L1 events and downloading relevant data.
- Executor: Executes EVM-compatible transactions and computes new state roots.
- EthTxManager: Handles all Ethereum interactions, including nonce management and dynamic gas pricing.
- State & StateDB: Manages persistent storage of batches, blocks, and transaction states.
- Pool: Temporarily holds incoming transactions before sequencing.
- JSON RPC: Provides developer-facing API endpoints.
- L2GasPricer: Dynamically calculates L2 gas prices based on L1 congestion.
Core Smart Contracts in Polygon CDK
Three primary contracts form the backbone of CDK-based chains:
CDKDataCommittee.sol
Manages DAC membership and signature validation.
setupCommittee(...): Allows admins to define required signatures and register DAC members.verifySignatures(...): Confirms whether a given hash has received enough valid signatures from authorized members.
CDKValidium.sol
Tracks and updates the L2 state on Ethereum.
sequenceBatches(...): Called by the trusted sequencer to submit new batches; validates DAC signatures viaCDKDataCommittee.verifyBatches(...): Accepts ZK proofs to finalize batches and update the global state root.
PolygonZkEVMBridge.sol
Facilitates cross-chain asset transfers between L1 and L2, supporting native token bridging and ERC standard tokens.
Data Flow in Polygon CDK
- Batch Assembly: Sequencer gathers user transactions into a batch.
- Batch Certification: Sends batch data + hash to DAC nodes.
- Validation & Storage: DAC nodes verify authenticity and store data locally.
- Signature Generation: Each DAC signs the batch hash upon successful validation.
- L1 Submission: Sequencer sends the hash and signatures to Ethereum.
- On-Chain Verification: L1 contract checks if sufficient valid signatures were provided.
- ZKP Finalization: Aggregator submits a ZK proof confirming batch validity—finalizing the state update on Ethereum.
This streamlined flow ensures high performance, low cost, and strong security guarantees.
Frequently Asked Questions (FAQ)
Q: Is Polygon CDK suitable for enterprise use?
A: Yes. With support for compliance, privacy, and customizable governance, CDK is ideal for enterprise-grade blockchains.
Q: How does DAC prevent data loss?
A: Multiple independent DAC members store copies of off-chain data. Even if some fail, others ensure availability.
Q: Can I switch from zkEVM to Validium later?
A: While possible, it requires redeployment due to architectural differences in data handling.
Q: Are CDK chains EVM-compatible?
A: Yes—fully compatible with existing Ethereum tooling, wallets, and dApps.
Q: What happens during an emergency state?
A: The system enters a safe mode where certain functions (like batch submission) are paused until resolved.
Q: How decentralized is the DAC?
A: Decentralization depends on member selection. Open or permissionless DACs enhance trustlessness.