When ZK technology is further popularized in areas such as Hybrid Rollup, ZK Cross-chain Bridge, and ZK Hardware Acceleration, the Layer2 market will have new vitality. This article is sourced from Haotian and is organized, translated, and written by Foresight News.
Table of Contents:
Hybrid Rollup
Trust mechanism based on ZK cross-chain bridge
Conclusion
Many people think that ZK-Rollup is the endgame of Ethereum Layer2, but as research deepens, I have found that the true endgame is not the ZK-Rollup form, but the ZK technology itself.
Because theoretically, OP-Rollup can also use ZK technology to reduce the 7-day challenge period and even eliminate the flaws of MPC multi-signature governance. How to understand this? This article will discuss this topic using “MetisL2” and its underlying hardcore project “ProjectZKM” as examples.
In a previous article, I also explained that the “ZK technology” for Layer2 scalability has only explored limited potential and there is still much room for improvement in terms of trustless and interactive operability in the entire chain. In specific Layer2 application scenarios, it can directly bring two major impacts:
1. The cross-chain of funds between Layer2 and Layer1 can directly rely on the ZK underlying technology to ensure the security of asset delivery. Using ZK technology, OP-Rollup can significantly shorten the 7-day waiting period for fund withdrawal challenges.
2. The Prover verification system of Layer2 and the Rollup verification contract of Layer1 can achieve the construction of a trusted environment across different chains. In theory, it is possible to no longer rely on centralized or semi-centralized MPC multi-signature governance, which is criticized as a “human governance” model, to ensure security.
In fact, “MetisL2” as a Layer2 chain based on the OP-Rollup technology framework has already achieved the normalization of the underlying architecture in these two dimensions through the ZK underlying technology:
1. On the one hand, by optimizing the user experience of Withdrawal by combining OP-Rollup and ZK-Rollup in a Hybrid Rollup framework, the waiting time for withdrawing funds from Layer2 to Layer1 can be reduced, allowing for faster release of liquidity.
2. On the other hand, by gradually implementing the “trustless” framework of “ProjectZKM” in cross-chain interoperability with Metis layer2 as the experimental target, a decentralized co-processor built on the ZK-based infrastructure is used as a trusted entity to generate proofs, verify proofs, and manage communication and trust mechanisms between cross-chain blockchain nodes. How is this done?
Under normal circumstances, a Layer2 either adopts the Rollup structure based on optimistic 7-day challenge period proof, or the proof structure based on ZK-SNARKs with single-block finality.
The former has fast batch transaction speed and low transaction fees, but the drawback is that when a user withdraws funds from Layer2 to Layer1, they need to wait for the 7-day challenge period. According to the optimistic batch essence of OP-Rollup, the withdrawal of funds can only be considered secure if it is not challenged and traced back within 7 days.
The latter, ZK-SNARKs, enables asset security confirmation in a single block, in addition to the cost of DA for batch transactions. However, the development threshold for the construction of the Layer2 ecosystem is higher, and the development speed of the ecosystem is slower.
So, how can we achieve both the usability of the overall OP-Rollup structure and avoid the limitation of the 7-day challenge period (locking liquidity)? The answer is to process the transactions of Batch returning from Layer2 to the mainnet through separate “channels”. Common transactions go through the OP-Rollup channel, while special Withdrawal transactions go through the ZK-Rollup channel. In this way, the advantages of both OP and ZK are adopted, resulting in an optimal solution.
Metis has already implemented the Hybrid Rollup solution in its chain operation process, and the “ProjectZKM” project, incubated and developed by the Metis technical team, provides this Hybrid Rollup capability. Underneath, there is an Entangled Rollup protocol to provide unified liquidity management services.
In fact, upstream service providers such as ProjectZKM, RiscZero, and SuccinctLabs are promoting similar technical solutions to further reduce the differences between OP-Rollup and ZK-Rollup, while reducing the liquidity loss caused by the 7-day challenge waiting period that has not been battle-tested. Notably, projects such as Metis, Fraxchain, Aztec, and Ola are exploring and implementing such Hybrid Rollup solutions.
Currently, most Layer2 projects are criticized for the centralized or semi-centralized governance committees controlling the mainnet Rollup contracts, which limits the security of most Layer2 projects to what Vitalik refers to as Stage 0.
Upstream service providers like ZKM and RISC Zero can theoretically create a decentralized trusted environment for cross-chain bridges without the need for MPC multi-signatures between every chain with smart contract capabilities.
The principle is simple: ZK-SNARKs allow nodes maintaining consensus on two chains to establish direct communication. When a node on chain A receives transactions and ZKP proofs submitted by a node on chain B, it can independently verify the validity of the ZKP proofs and accept the validity of the proofs submitted by chain B. The entire process is achieved solely through zero-knowledge proof algorithms and does not require a third-party controlling entity.
As for the co-processor that handles communication between scheduling nodes, it can be implemented using a decentralized open-source architecture, thereby completely solving the “centralization” problem of Rollup cross-chains.
Since Ethereum has complete smart contract capabilities, theoretically, every Layer2 of Ethereum has the basic conditions for cross-chain based on ZK technology. Ideally, all Layer2 solutions should adopt the same set of ZK technology frameworks for cross-chain solutions, and other Layer1 and even Layer3 chains should also be incorporated into this network communication framework. In the future, the Ethereum mainnet will become a universal settlement layer in a fully connected environment.
The reason why most Layer2 projects currently do not want to abandon MPC multi-signature governance is mainly due to the need for security control. In my opinion, the fundamental reason is that the popularization of decentralized sequencers, decentralized Provers, and decentralized zkBridges, and other fundamental components of the Layer2 layer, is not yet in place. In this situation, retaining centralized or semi-centralized governance committees has become a safer governance method.
However, in the long run, as decentralized components in Layer2 become more popular, the security governance of Layer2 will inevitably be criticized, and a cross-chain settlement solution based on ZK technology will become necessary. The future development potential of the ZK technology infrastructure track can be imagined.
To put it plainly, Ethereum Layer2 is currently facing development challenges: either rely on a phenomenon-level project from the Layer2 or Layer3 application ecosystem to boost market confidence in Layer2, or continue to improve the decentralization of key components such as Sequencers, Provers, and zkBridges to sustain technical narratives.
And the latter path will inevitably require an underlying framework based on ZK technology to bridge the gap. Without the distinction between OP-Rollup and ZK-Rollup, the endgame characteristics of ZK will truly emerge.
Only by following this path can the development direction of Layer2 be proven genuine, and it can also extend to the development of various narrative directions such as ZK hardware device acceleration, ZK+DePIN support for PC, mobile, IOT devices, ZK tamper-proof cloud computing data protection, and the construction of a decentralized Prover system based on ZK and optimization of computing resources.
In fact, at the intersection of the AI, ZK, and DePIN tracks, there are already many similar projects that are gradually gaining prominence.
Metis’s development strategy in Layer2 and the original intention of the hardcore ZKM project are also based on this, making ZK technology more universally applicable to every aspect of the global Layer2 market. In addition to Metis, I have also noticed other projects, such as “cysic_xyz”, which continues to cultivate ZK hardware and chip acceleration, and “ola_zkzkvm”, which is gradually implementing a decentralized Prover system based on ZK.
To summarize, I want to reiterate my viewpoint that the application of ZK technology in the Layer2 field is just the tip of the iceberg. When ZK technology is further popularized in areas such as Hybrid Rollup, ZK Cross-chain Bridge, and ZK Hardware Acceleration, it will undoubtedly bring new vitality to the Layer2 market.
After all, it will take a long time for the entire Layer2 market to accept this ZK-based bottom-up upgrade.