Layer2: The Battle of Rollup Technology

Layer2 is one of the key solutions designed to address the scalability issues of Ethereum. By building an additional network layer on top of the Ethereum main chain, Layer2 can handle more transactions while maintaining the security and decentralization features of the main chain.

Rollup is a Layer 2 scaling solution that processes transactions off-chain and then "packages" the data into the main chain. Compared to other off-chain transaction solutions, Rollup has three main characteristics:

1. Layer2 is a relatively independent platform where users can trade on it, but interaction with Layer1 accounts needs to be achieved through smart contracts.

2. All transaction information will be fully recorded on the main chain to ensure data availability.

3. Transactions are executed on Layer 2, but the state summary will be published on Layer 1 blockchain for verification.

Depending on the different data verification methods, Rollups can be divided into Optimistic Rollups and ZK Rollups.

Development History of Rollup

Early Layer 2 solutions include sidechains and Plasma. Sidechains are independent blockchains that are linked to the main chain. Plasma, proposed by Joseph Poon and Vitalik Buterin in 2017, is an extension solution and an evolved version of sidechains.

Plasma chain is built outside of Ethereum, forming a tree-like network structure. It breaks down large computing tasks and allocates them to child chains for processing, improving computational efficiency. However, Plasma faces issues such as data availability attacks, exit delays, and high monitoring costs.

In 2019, John Adler proposed the Optimistic Rollup solution, which mainly addressed the data availability issues of Plasma. Around the same time, Vitalik Buterin introduced zero-knowledge proof technology to verify block state changes, laying the groundwork for ZK Rollup.

The development of ZK Rollup technology benefits from the advancements of algorithms such as zk-SNARK and Plonk. The Plonk algorithm addresses the trusted setup issue of zk-SNARK, greatly promoting the development of ZK Rollup.

Rollup Main Plan

Optimistic Rollups

Optimistic Rollups assume that most transactions are valid, allowing for challenges and rollbacks when fraud is detected. The main representatives are Arbitrum and Optimism.

Arbitrum launched its mainnet in September 2021 and is currently the Layer 2 protocol with the highest TVL. Its ecosystem includes three networks: Arbitrum One, Arbitrum Nova, and Arbitrum Orbit.

Optimism launched its mainnet in August 2021, holding the second largest TVL in Layer 2. It achieved EVM equivalence and launched the open-source modular toolkit OP Stack, which supports building customized Layer 2 networks.

ZK Rollups

ZK Rollups use zero-knowledge proof technology to ensure the validity and correctness of off-chain transaction processing. Major representatives include zkSync, StarkNet, Polygon zkEVM, and Scroll.

zkSync is the first zkEVM project to launch on the mainnet, supporting technologies such as "optimistic" transfers and signature aggregation.

StarkNet uses zkSTARK scaling solutions and sharding technology to improve privacy, security, and throughput.

Polygon zkEVM achieves compatibility with Ethereum at the bytecode level, providing faster and cheaper transactions.

Scroll is an EVM-compatible ZK Rollup that supports seamless migration of existing applications.

Outlook

In the short term, Optimistic Rollups may dominate general EVM computations, while ZK Rollups may perform better in simple payments and specific application scenarios. In the long run, with advancements in ZK-SNARK technology, ZK Rollups are expected to become the ultimate solution for Ethereum scaling.