Understand Scroll in Three Minutes: A New Contender for ZK Rollup Scaling

Author: iambabywhale.eth, ForesightNews

As the Ethereum Layer 2 networks Optimism and Arbitrum are thriving due to the launch of governance tokens and the Arbitrum Odyssey event in collaboration with Project Galaxy, the ZK Rollup-based Layer 2 networks, which have been highly regarded by Ethereum founder Vitalik Buterin, seem to be less prominent.

This situation arises partly because the development of ZK Rollup-based networks is more challenging, with most still in the testing phase; on the other hand, their security has yet to be validated through practical experience, and there are certain development difficulties in migrating applications to Ethereum.

The founder of Scroll stated that the aim of establishing Scroll is to optimize the current ZK Rollup solutions and create a Layer 2 network that allows seamless migration of applications on Ethereum.

Project Financing and Team

According to a report by The Block in April this year, Scroll completed a $30 million Series A funding round led by Polychain Capital, with participation from Bain Capital Crypto, Robot Ventures, Geometry, and several members of the Ethereum Foundation's zkEVM Team. The founding team includes Sandy Peng, Ye Zhang, and Haichen Shen.

Co-founder Ye Zhang mentioned that he has been researching ZKP for four years, with his first project focused on accelerating ZKP using FPGA and ASIC. Afterward, Ye Zhang began studying the mathematics and cryptography behind ZKP and became interested in its applications in the blockchain space. He stated that the development of the Scroll network was prompted by discovering some issues with ZK Rollup early last year, and his research direction happened to align with solving these problems.

Sandy Peng graduated from the University of Cambridge and previously worked in research at the Hong Kong Securities and Futures Commission. Since 2017, she has been involved in Web3 project investments. Currently, she is responsible for business development, financing, and ecosystem matters at Scroll.

Haichen Shen studied in Tsinghua University's Yao Class for his undergraduate degree and earned his Ph.D. from the University of Washington, focusing on underlying systems (including GPU, PL, compiler, and other intersecting fields). After graduation, he worked at Amazon on building machine learning systems.

What Problems Does Scroll Aim to Solve?

Currently, the Scroll project is still in a relatively early stage, with limited public information available. Through interviews with the project team, I have gathered some insights about the project, which are summarized here:

Why Use ZKP to Build a Layer 2 Network?

The Scroll team stated that there are three reasons for using ZKP to establish a Layer 2 network.

First, the currently leading Optimistic Rollup at the application layer relies on a "fraud proof" that includes economic incentives to ensure security. Although the security model based on economic incentives has been validated by the market to some extent, it is not completely secure; it relies on the assumption of honest nodes, meaning there is still a theoretical possibility of being attacked. Additionally, due to this assumption, withdrawals from L1 to L2 require approximately seven days of waiting time. In contrast, ZK Rollup can achieve theoretically complete security through mathematics (theoretically, assuming there are no vulnerabilities in the code), and even the slowest withdrawals only require about an hour for proof generation. Therefore, ZK Rollup offers better security and shorter L1 withdrawal times.

Second, ZKP inherently has the ability to compress and verify large amounts of information, and it can achieve decentralized verification by distributing ZKP computation tasks in a fair manner. This aligns with the vision of a "decentralized efficient blockchain" both in form and effect. Furthermore, the team indicated that for certain specific applications (such as DEX), their ZKP-based Layer 2 network would theoretically be much faster than Optimistic Rollup-based Layer 2 networks, as the on-chain data can be further compressed.

The final point is that ZKP, in addition to improving efficiency, may open up greater possibilities for the future (such as capabilities in privacy protection). The team noted that the advantages in this area are currently only in the theoretical validation stage, and whether they can be realized and in what manner remains unknown and requires further research exploration.

Scroll Plans to Establish EVM Equivalent zkEVM

The Scroll team stated that EVM equivalence is a concept first proposed by Optimism, meaning that applications on Ethereum can seamlessly migrate to Optimism without excessive modifications to the code. However, the current solutions from StarkWare and zkSync have rebuilt a virtual machine that is only "language-compatible" with EVM, meaning that while it can use languages like Solidity for compilation, a certain degree of redevelopment is required.

We can glimpse some insights from the actual situation. StarkNet just announced last month the opening of a cross-chain bridge with Ethereum, but in practice, we found that the address format on StarkNet is different from Ethereum addresses on MetaMask, requiring users to connect to the Argent X browser extension wallet to achieve cross-chain functionality.

What Scroll aims to do is similar to Polygon Hermez, hoping to achieve compatibility at the "ByteCode" level, meaning that applications on Ethereum can almost seamlessly migrate to the Layer 2 network. Additionally, the team stated that this level of compatibility would allow for compatibility with all languages on Ethereum and also with Ethereum tools, significantly reducing the development difficulty on the Layer 2 network.

Decentralized Verification Network

Given that the co-founders have experience in ZKP hardware acceleration, Scroll plans to utilize hardware acceleration in ZKP to further improve verification efficiency. The team expressed their vision of establishing a decentralized verification network that distributes ZKP proofs to participants for computation and aggregates the results to form the final proof. This decentralized verification network will be open to everyone and will implement incentive and penalty mechanisms (for example, introducing redundancy in computation results, such as distributing the same computation content to several nodes for comparison and punishing malicious nodes).

The team stated that this decentralized verification network fully embodies the spirit of blockchain and guarantees security at the cryptographic level. Compared to PoS-like verification networks and the currently somewhat centralized transaction verification and block production mechanisms of Layer 2 networks, ZK Rollup is a superior choice, but as mentioned earlier, the development difficulty is also higher.

Conclusion

In addition to the above content, the team also revealed that they are collaborating with Flashbots to explore solutions to reduce the harm of MEV on user experience, and they will also explore more non-financial applications at the application layer in the future.

The combination of ZKP and blockchain was first initiated by the launch of Zcash, and the industry continues to actively explore and research this area. Besides Layer 2 networks, application-oriented projects like Filecoin also utilize ZKP in their verification processes. Although large-scale adoption may still lack some theoretical support, it still holds promise as one of the technologies that can achieve Layer 2 network security at the cryptographic level while ensuring security on a PoW-based Layer 1 network.