Breaking through Layer2: How can upstream ZK technology services release new market momentum?

Original author: Haotian

Many people think that ZK-Rollup is the endgame of Ethereum layer 2. However, as I delved deeper into the research, I found that it is not the ZK-Rollup form that can be called the endgame, but the ZK technology itself. Because in theory, OP-Rollup can also use ZK technology to reduce the time limit of the 7-day challenge period, and even eliminate the MPC multi-signature governance defects. How to understand it? This article will take @Metis L2 and the technical hardcore project @ProjectZKM behind it as an example to discuss:

In a previous article, I also explained that the potential of "ZK technology" for layer 2 expansion has only been tapped to a limited extent, and there is still a lot of room for full-chain trustless interoperability. In the context of layer 2 application scenarios, it can directly bring two major impacts:

1) Cross-chain funds between layer 2 and layer 1 will be able to directly make deterministic delivery of secure assets based on ZK underlying technology. Using ZK technology, OP-Rollup can significantly shorten the 7-day waiting challenge period required for fund withdrawal;

2) The Prover verification system of layer 2 and the Rollup verification contract of layer 1 can realize the construction of a trusted environment across the main chain. In theory, there is no need to use the "rule of man" model such as centralized or semi-centralized MPC multi-signature, which is criticized, to ensure security;

In fact, @Metis L2, as a layer 2 chain based on the OP-Rollup technical framework, has already achieved the above two dimensions of layer 2 underlying architecture paradigm transition through ZK underlying technology:

On the one hand, the hybrid Rollup framework of OP-Rollup+ZK-Rollup optimizes the user experience of waiting 7 days for withdrawing coins, which can release liquidity faster;

On the other hand, the experimental goal is to gradually implement @ProjectZKM's "trustless" framework for cross-chain interoperability, using ZK as a decentralized coprocessor built on the infrastructure as a trusted subject to generate proofs, verify proofs, and manage the communication and trust mechanism between cross-chain blockchain nodes. How to do it specifically?

Hybrid Rollup

Under normal circumstances, a layer 2 is either an OP-Rollup with a Rollup structure based on an optimistic 7-day challenge period proof, or a ZK-Rollup with a single-block Finality proof structure based on ZK-SNARKs.

The former has a fast batch transaction rate and low handling fee. However, the disadvantage is that when users withdraw funds from Layer 2 to Layer 1, they need to wait for a 7-day challenge waiting period. According to the optimistic batching principle of OP-Rollup, only if the withdrawal funds are not challenged and traced back within 7 days, the withdrawal of the funds can be considered safe in theory.

The latter ZK-SNARKs' Proofs transmission structure can achieve Finality asset security confirmation in a single block. The disadvantage is that in addition to the DA cost of Batch transactions, the Prover system calculation and verification costs will be added. In addition, the two-layer ecological construction has a high starting threshold for the developer team, and the ecological development speed is slow.

So, how can we apply the ease of use of the OP-Rollup overall architecture while being free from the limitation of its 7-day challenge period (locking liquidity)? The answer is: divide the transactions from the 2-layer batch back to the main network into "channels", with Common transactions going through the OP-Rolluo pipeline and special Withdraw transactions going through the ZK-Rollup pipeline. In this way, the strengths of both OP and ZK are adopted, becoming a compromise optimal solution.

Metis has implemented the hybrid Rollup solution into the normal operation of its chain, and the "new" hard-core ZK technology underlying project @ProjectZKM incubated and created by the Metis technical team provides it with this hybrid Rollup capability. The Metis team discovered some inherent normal problems in the process of operating layer 2. In addition to taking the lead in overcoming the decentralized sequencer problem, it also aims to solve a series of problems in the development of layer 2 through ZKM, such as "MPC semi-centralization" and "locking liquidity";

At first glance, you may find it very abstract. The reason is what I explained in my previous article about ZK technology. This type of service is still at the upstream of the layer 2 technology service supply chain. Although it is hardcore, it has not been widely adopted, so it sounds unfamiliar. ZKM, like RISC Zero, aims to provide upstream security consolidation services for layer 2 projects based on the ZK underlying technology framework.

Currently, ZKM provides the ZK-Rollup pipeline service for the hybrid Rollup required by layer 2. There is also an Entangled Rollup protocol at the bottom layer to provide unified liquidity management services.

In fact, upstream ZK technology service providers such as @ProjectZKM, @RiscZero, and @SuccinctLabs are promoting the popularization of similar technical solutions, thereby helping OP-Rollup and ZK-Rollup to further reduce differences, while reducing the loss of liquidity caused by the 7-day challenge waiting period when there is no Battle-Tested challenge at all. According to incomplete statistics, Metis, Fraxchain, Aztec, Ola, etc. have been exploring the implementation of such hybrid Rollup solutions.

Based on ZK cross-chain bridge-free trust mechanism

Now most layer 2s are criticized for the problem that the Update proxy contract of the mainnet Rollup contract is controlled by the semi-centralized MPC security governance committee, which causes most layer 2 security to remain in the Stage 0 stage as Vitalik said.

Upstream ZK technology service providers such as ZKM and RISC Zero can, in theory, enable the construction of a decentralized trusted environment for MPC-free multi-signature cross-chain bridges between every chain with smart contract functions.

The principle is very simple. ZK-SNARKs allows the nodes maintaining consensus on the two chains to establish direct communication. After receiving the transaction and ZKP proof submitted by the node of chain B, the node of chain A can independently verify the validity of the ZKP proof and then accept the validity of the Proofs submitted by chain B. The whole process is completely implemented by the zero-knowledge proof algorithm and does not require a third-party human subject to control.

As for the coprocessor that schedules communication between nodes, it can be implemented using a decentralized open source architecture, thereby completely solving the "centralization" problem that exists in Rollup cross-chain.

Since Ethereum has the completeness of smart contracts, in theory, Ethereum's layer 2 has the basic conditions for cross-chain based on ZK technology. Ideally, layer 2 uses the same ZK technology framework to deploy cross-chain solutions, and other layer 1 chains and even layer 3 chains are also incorporated into this network communication architecture. Wouldn't the Ethereum public chain in the future become a universal settlement layer in a full-chain environment?

The reason why most layer 2 project parties are unwilling to give up MPC multi-signature subject management is mainly due to security control needs. In my opinion, the fundamental reason is that the basic component services such as decentralized sequencer, decentralized prover and decentralized zkBridge at the entire layer 2 level are not popular enough. In this case, retaining a centralized or semi-centralized security governance committee has become a safer governance method.

However, in the long run, as layer 2 becomes more popular in decentralized components, layer 2 security governance will certainly be criticized, and a cross-chain settlement solution based on the ZK underlying layer will become a necessity. The subsequent development potential of the ZK technology infrastructure track can be imagined.

above

It is no exaggeration to say that Ethereum layer 2 is currently stuck in a development dilemma: either rely on the application ecosystem of layer 2 or layer 3 to produce a phenomenal project to boost market confidence in layer 2, or rely on further improving the decentralization of key components such as sequencer, prover, and zkBridge to continue to enrich the technical narrative. The latter will inevitably require a set of underlying frameworks based on ZK technology to connect. Without the distinction between OP-Rollup and ZK-Rollup, the Endgame feature of ZK will truly emerge.

Only by following this path can the development direction of layer 2 not be falsified, and based on this, it can also extend the development of ZK hardware device acceleration; ZK+DePIN PC, mobile, IOT and other hardware device support; ZK tamper-proof cloud computing data protection; ZK decentralized Prover system construction and computing power resource optimization and many other narrative directions.

In fact, at the intersection of AI, ZK, and DePIN, there are already many similar projects that are becoming increasingly prominent.

The same is true for Metis' development ideas in layer 2 and the original intention of the hardcore ZKM project, which is to make ZK technology more universal and applicable to every link in the construction of the global layer 2 market. In addition, my personal investment research has also noticed some projects, such as @cysic_xyz, which continues to work on ZK hardware and chip acceleration, and @ola_zkzkvm, which is gradually implementing the ZK Prover decentralized computing system.

In short, I would like to reiterate my point of view that the current application of ZK technology in the layer 2 field is just the tip of the iceberg. When ZK technology is further popularized in the fields of hybrid Rollup, ZK cross-chain bridge, ZK hardware acceleration, etc., I believe it will also bring new vitality to the layer 2 market.

After all, it will take a long time for the entire layer 2 market to accept this ZK bottoming upgrade paradigm.