Polygon’s Scalability Spectrum: Comparing PoS, zkEVM Rollups, and Validium
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The blockchain trilemma, a term coined by Ethereum creator Vitalik Buterin, posits that it’s challenging to achieve scalability, security, and decentralization all at once. As Ethereum has grown, scaling solutions, commonly referred to as “Layer 2” (L2) solutions, have been developed to address the scalability challenge without compromising on security or decentralization. In this post, we’ll compare three such solutions: Polygon’s Proof of Stake (PoS), zkEVM Rollup, and zkEVM Validium, shedding light on how they function and their relative trade-offs.
Polygon PoS: The Multi-Chain System
Polygon PoS is a sidechain solution that runs parallel to the Ethereum mainnet. It uses a Proof of Stake consensus mechanism, which is a more energy-efficient alternative to Ethereum’s original Proof of Work system.
How It Works:
- Transactions are bundled on the Polygon network, which has its validators to secure the network.
- Periodically, checkpoints of the bundled transactions are submitted to the Ethereum mainnet.
- Security is provided by a set of validators who stake MATIC tokens, Polygon’s native cryptocurrency, as collateral.
Pros:
- High Throughput: Polygon PoS can handle a higher number of transactions per second (TPS) compared to Ethereum.
- Low Fees: Transaction costs are significantly lower than on Ethereum’s mainnet.
- Ecosystem Growth: Polygon PoS has seen widespread adoption and supports a rich ecosystem of decentralized applications (dApps).
Cons:
- Security Trade-off: While Polygon’s security is robust, it still relies on a smaller set of validators, which makes it less secure than Ethereum’s extensive network.
- Finality Dependency: Finality on the Polygon PoS chain depends on the main Ethereum chain for checkpointing, which can introduce delays.
zkEVM Rollup: Scalability Meets Ethereum Compatibility
zkEVM Rollups are an emerging L2 solution that uses zero-knowledge proofs to roll up transactions off-chain and submits a cryptographic proof of their validity to the main Ethereum chain.
How It Works:
- Transactions are executed and processed off-chain in a zkEVM-compatible environment.
- A zero-knowledge proof (zk-SNARK — Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) is generated for batches of transactions, proving their validity without revealing underlying data.
- The zk-SNARK is submitted to the Ethereum mainnet, effectively compressing many transactions into a single proof.
Pros:
- Ethereum Compatibility: zkEVM Rollups aim to be compatible with existing Ethereum smart contracts without requiring significant changes.
- Enhanced Privacy: The use of zero-knowledge proofs provides an additional layer of privacy for transactions.
- Reduced Costs: By batching many transactions into a single proof, zkEVM Rollups significantly reduce transaction fees.
Cons:
- Computational Overhead: Generating zk-SNARKs is computationally intensive, which can lead to higher costs and longer wait times for proof generation.
- New Technology: zkEVM is a relatively new technology and may face growing pains and challenges in adoption.
zkEVM Validium: Maximizing Scalability and Data Availability Options
zkEVM Validium is another variant of zkEVM that opts to use external data availability, separating the data layer from the Ethereum main chain.
How It Works:
- Like zkEVM Rollups, transactions are grouped and processed off-chain, and a zk-SNARK is created.
- Instead of posting the data on-chain, Validium stores transaction data off-chain in a decentralized data availability committee or other secure storage.
- Only the zero-knowledge proof is submitted to the Ethereum mainnet, referencing the off-chain data.
Pros:
- Even Lower Fees: Since transaction data isn’t stored on-chain, the fees are further reduced compared to zkEVM Rollups.
- Scalability: It offers even greater scalability potential than zkEVM Rollups by off-loading more data from the main chain.
Cons:
- Data Availability Trade-off: The security assumption changes with Validium as it relies on external parties for data availability, which can introduce new risks.
- Complexity: Managing off-chain data requires additional infrastructure and poses extra challenges in ensuring that data remains accessible.
Conclusion
The choice between Polygon PoS, zkEVM Rollup, and zkEVM Validium ultimately boils down to the specific needs and preferences of users and developers. Polygon PoS offers a robust, battle-tested environment with high throughput and an established ecosystem. zkEVM Rollups provide a promising solution that balances scalability with Ethereum’s security and decentralization principles. Meanwhile, zkEVM Validium pushes the boundaries of scalability even further, with the trade-off of relying on external data availability solutions.
As the blockchain space evolves, we may see these solutions converge, with each learning from the others