Blockchains grapple with scalability issues, which lead to slow transaction processing times and high costs. To address this long-standing issue, zero-knowledge (ZK) rollups have emerged as a promising solution.
ZK rollups are Layer-2 solutions that bundle multiple transactions off-chain and submit a concise proof of their validity to the main blockchain. This proof, generated using zero-knowledge cryptography, verifies that the off-chain transactions are legitimate without revealing their details.
In doing so, the computational load on the main blockchain is reduced, resulting in faster and more cost-effective transaction processing while maintaining security and decentralization.
But what are the distinct types of ZK Rollups, and where do they find practical application?
In this blog, we’ll discuss various ZK Rollup networks, compare their features, and list out popular dApps that leverage these scaling solutions.
How do ZK rollups work?
ZK Rollups operate by processing transactions off-chain and then recording the results on the main blockchain in a compressed format. This process involves two key components: the core infrastructure and the execution process.
The core infrastructure includes on-chain contracts and an off-chain virtual machine.
- The on-chain contracts, deployed on Ethereum, are responsible for storing rollup blocks and managing state updates.
- The off-chain virtual machine, on the other hand, handles the computation and storage of transactions.
This separation allows for efficient processing while maintaining security through Zero-Knowledge Proofs (ZKPs).
In the execution process, sequencers batch multiple transactions and submit them to the ZK rollup contract. The transactions are processed off-chain, and validity proofs are generated to confirm their correctness.
Then, these proofs like zk-SNARKs or zk-STARKs are generated, and submitted to Ethereum, where it's checked by the verifier contract. If the transaction is valid, the new state is accepted and recorded on the Ethereum blockchain.
5 popular ZK rollup projects
Below, we’ve highlighted five of the most popular and influential ZK Rollup projects that are making waves in the blockchain ecosystem.
Linea is a ZK rollup-based Layer 2 network that enables developers to deploy new or existing Ethereum applications on Linea without rewriting or adapting the code.
It has a three-part architecture consisting of:
- Sequencer: Responsible for executing transactions, batching them, and submitting them to the network.
- Prover: Generates zero-knowledge proofs to validate the correctness of transactions processed by the Sequencer.
- Bridge relayer: Facilitates the transfer of data between Linea and other networks, including the Ethereum Mainnet.
The benefits of using Linea are:
- Linea can generate ZK-proofs directly from Solidity’s compiled byte code. This approach reduces the risk of introducing bugs and vulnerabilities that might occur during the process of translating or adapting code for a different platform.
- Linea is built to provide a user experience that is very similar to Ethereum; developers and users can use the same wallets, tools, and interfaces they are accustomed to when interacting with Ethereum. That means they can transition to Linea easily.
Scroll is a Type-3 zkEVM solution that focuses on security, transparency, and creating a reliable, decentralized infrastructure that aligns closely with Ethereum's principles and user experience.
It has a three-part architecture consisting of:
- Settlement layer: This foundational layer integrates with Ethereum, ensuring data availability and order for Scroll's operations. It plays a crucial role in verifying the validity proofs and facilitating the transfer of messages and assets between Ethereum and Scroll.
- Sequencing layer: At this layer, the Execution Node processes transactions directed to the Scroll sequencer and those from the Ethereum bridge contract, creating L2 blocks. Additionally, the Rollup Node batches these transactions, posts their data to Ethereum for transparency, and submits validity proofs to Ethereum, ensuring the finality and integrity of the transactions.
- Proving layer: This layer is composed of a network of provers that generate zkEVM validity proofs to confirm the accuracy of L2 transactions. Once verified, a coordinator in this layer assigns proving tasks and conveys the generated proofs to the Rollup Node for finalization on the Ethereum blockchain.
Here are the benefits of building on Scroll:
- Decentralized proving: Scroll allows anyone to become a roller by staking SCR, its native token. This decentralized approach ensures that the proving process is not controlled by a small group of entities.
- Low cost of proving: Scroll employs innovative techniques to reduce the cost of proving, making it feasible for participants with limited computing resources to join the roller network.
Polygon has developed a suite of zero-knowledge rollups (ZK rollups) to enhance throughput on Ethereum without compromising decentralization or security. Here are the different Polygon ZK rollup solutions:
- Zero: Zero is an EVM-compatible rollup solution that employs a recursive proof system called Plonky2 to reduce the computational cost associated with generating validity proofs.
- Hermez: Hermez utilizes a unique 'Proof of Efficiency' system that enables users to serve as sequencers (batching transactions) or as aggregators (responsible for ZK proof generation). This model significantly reduces centralization risks and reduces the chances of malicious activity on the network.
- Nightfall: Polygon Nightfall combines optimistic rollups with zero-knowledge cryptography to facilitate private transactions for institutions.
- Miden: Miden is a general-purpose STARK-based ZK rollup that executes smart contracts locally and submits only the proofs to the network. This design enables parallel processing of transactions, markedly enhancing efficiency and scalability. Also, unlike other STARK-based rollups, Miden is EVM-compatible. This simplifies the development process.
- zkEVM: Polygon’s zkEVM solution is EVM-equivalent which means it maintains opcode compatibility with the Ethereum Virtual Machine thus enabling developers to bring their smart contracts to the network with minimal support.
- Polygon 2.0: Polygon 2.0 upgrades the existing Polygon PoS network into a zkEVM validium, integrating zero-knowledge proofs for enhanced security and performance. This transition results in significantly lower fees and higher scalability, without altering the user and developer experience.
Here is a prominent benefit of using Polygon’s ZK Rollups:
- Swift proof generation: Polygon’s ZK rollups dramatically accelerate the process of generating validity proofs. This ensures faster transaction processing and enhances the overall user experience on the network.
StarkNet uses a proprietary proof system called zk-STARK to ensure transaction correctness without revealing sensitive data. This improves the privacy and security of dApps.
Its architecture consists of:
- User accounts: Implemented as smart contracts and offer more flexibility than Ethereum's Externally Owned Accounts (EOAs). This allows for the creation of better wallet recovery mechanisms.
- Sequencer: An off-chain component that receives, orders, validates, and bundles transactions into blocks.
- Prover: Generates cryptographic proofs attesting to the integrity of computations performed by the Sequencer.
- Full nodes: Keep a record of all transactions and track the current global state of the system.
- Verifier and core smart contract: On-chain components where the Verifier validates proofs and the Core contract records state changes.
Here are the benefits of using StarkNet:
- Native Account Abstraction (AA): In StarkNet, AA is integrated at the protocol level and merges Externally Owned Accounts (EOAs) and Smart Contract Accounts (SCAs). This simplifies the development process as developers can treat all accounts as if they have smart contract capabilities. In other words, there’s no need to reprogram EOAs into SCAs
- Reduced transaction costs: StarkNet significantly lowers transaction fees on Ethereum by optimizing the Layer 1 calldata costs, which often constitute up to 95% of the total transaction expense.
zkSync Era is an advanced version of the zkSync protocol that’s designed to be more efficient and scalable. It supports nearly all smart contracts based on the Ethereum Virtual Machine (EVM), which provides a more robust and user-friendly experience.
Here are some benefits of using this solution:
- Enhanced scalability and efficiency: zkSync Era's architecture, particularly its efficient handling of smart contracts and memory management, leads to improved scalability and efficiency compared to traditional Ethereum and previous versions of zkSync.
- Improved security and developer experience: By supporting almost all EVM-based smart contracts and minimizing the need for repeated security audits, zkSync Era offers a more secure environment and a better experience for developers.
Comparison of different ZK rollup solutions
5 apps utilizing ZK rollups
Here are five applications that leverage various ZK rollup solutions.
ZigZag Exchange is a decentralized exchange (DEX) that leverages the power of Zk rollup to optimize its order book and provide users with an unparalleled trading experience.
By employing the zkSync protocol, the DEX ensures that users can execute transactions with minimal fees, providing a fast and secure trading environment. This approach also enables ZigZag to offer its users the same competitive quotes as centralized exchanges, irrespective of the order size.
- Cost-Efficient trading
- Comparable quotes
Comoco is a Starknet-empowered project that is building the NFT IP infrastructure of the future. With a commitment to seamless NFT trading and licensing for boundless creativity, the platform introduces Blockchain-Enabled AI Models, elevating innovation across sectors.
Additionally, Comoco’s Blockchain-powered code and API solutions transform the conventional landscape, providing enhanced security, transparency, and efficiency in software development and utilization.
- Innovative NFT trading
- Efficient blockchain solutions
Arthur Exchange is a launchpad and DEX, revolutionizing decentralized finance (DeFi) on Linea's blockchain. As the inaugural launchpad, Arthur aims to enrich the Linea ecosystem and support new protocols.
For DEX transactions, the exchange leverages a dual automated AMM framework. This model introduces directional fees that empower users to navigate decentralized trading with unprecedented flexibility and efficiency.
- Enriching Linea ecosystem
- Advance AMM flexibility
Meson facilitates cross-chain transactions by leveraging ZK rollup technology, ensuring swift and cost-efficient transactions. The platform boasts a rapid 1-2 minute swap completion time, ensuring efficient transactions. It also introduced meta transactions that enable users to bypass gas fees and LPs to cover costs.
Additionally, Meson uses Atomic Swap technology for trades, ensuring assets stay in users' control without reliance on third-party involvement.
- Swift transactions
- Cost optimization
Powered by Starknet's cutting-edge zk-rollup technology, zkLend is a money-market platform that aims to transform DeFi. It is permissionless, allowing users to seamlessly deposit and borrow digital assets through their wallets, earning yields on lent assets.
Users can also employ deposited assets as collateral for additional borrowing, with no lock-up periods. This feature redefines DeFi accessibility, providing an efficient ecosystem for users to participate in liquidity provision and asset borrowing.
- Seamless deposits and borrows
- Collateralized borrowing with no-lock-up periods
The Future of ZK Rollups
By efficiently processing transactions off-chain and reducing the load on main blockchains, ZK Rollups offers a scalable, secure, and cost-effective solution.
As these technologies continue to evolve and integrate with various applications, from finance to gaming, they are set to redefine the efficiency and accessibility of blockchain networks.
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