Background

On April 10th, A16z Crypto released the zero-knowledge solution Jolt to accelerate and simplify blockchain scaling operations. Jolt integrates SNARK (Succinct Non-interactive Argument of Knowledge), allowing developers to quickly create SNARK-based L2 solutions. The team also stated that Jolt is twice as fast as current zkVMs. ZK technology has been one of the main threads in the crypto industry, with ZK-Rollup being hailed by Vitalik as a long-term solution for Ethereum scalability. A16z’s launch of Jolt from August last year to its official release this year indicates that ZK-Rollup is still a long-term track that requires arduous effort. ZK-Rollup has attracted many players, forming more refined technical categories to differentiate between projects. Its compatibility with EVM is the most representative classification standard.

EVM, due to historical reasons, has many ZK-unfriendly designs. However, many existing projects were built on EVM in the early stages, and ZK-Rollup is still seen as a future scalability solution. Therefore, the vast majority of ZK-Rollup projects naturally face the trade-off between being more compatible with EVM or more compatible with ZK.

ZKM incubated by Metis DAO takes a more fundamental approach and proposes a universal zkMIPS solution. zkMIPS achieves the conversion from the program execution process to ZKP by using a lower-level MIPS instruction set. In addition to compatibility with EVM, it can also be compatible with other VMs, such as MoveVM and RustVM, allowing ZK-Rollup to open its doors to a more diverse range of developers.

This article will provide readers with an in-depth understanding of Metis’ efforts and progress in ZK and decentralized Sequencer.

ZKM and Hybrid Rollups: A Blend of OP and ZK

Metis’s remarkable performance in the market is inseparable from its innovative Hybrid Rollups mechanism, which combines fraud proofs and validity proofs to embody the advantages of both.

ZKM’s zkMIPS technology provides solid compatibility support for Metis’s Hybrid Rollups, enabling Metis to achieve organic integration of ZK and EVM.

2.1 Mechanisms and Advantages of Hybrid Rollups

In Hybrid Rollups, key roles include:

• Sequencer: Responsible for receiving and processing user transactions, determining the optimal order of transactions, and packaging them for release to the consensus and data availability layers.
• Proposers: Evaluate transactions and state roots submitted by Sequencer and record them in the State Commitment Chain (SCC).
• Verifiers: Verify the state roots on the Rollup chain to ensure the correctness of transactions and prevent fraudulent behaviour.

In standard L2 solutions, the Sequencer collects and processes transactions, and then publishes transaction data to the Ethereum mainnet (L1). This process requires final data validation and confirmation by L1 to ensure security and consistency.

Source: https://mirror.xyz/msfew.eth/WQJaOcFkpTOZLns8MBQaCS4OepRoaZ7uoctnLAnalVw

Hybrid Rollups takes a hybrid approach when processing and optimizing L2 transactions. The specific steps are as follows:

1. Transaction initiation and processing:

• Users initiate transactions at L2.
• The Sequencer receives and processes these transactions and determines their order in the Canonical Transaction Chain (CTC).

1. Status submission and verification:

• Proposers evaluate the transaction and submit the state root to the SCC.
• Verifiers review the state root in the SCC to ensure it is accurate.

1. Generation and verification of zero-knowledge proof:

• Prover reads data from L1 and generates ZK proof. This is a key feature of Hybrid Rollups, allowing the system to verify the validity of the transaction without revealing the specific transaction content.
• Once the ZK proof is generated, the Verifier will start the fraud proof process and may punish the Sequencer if it is not submitted on time.

1. Final confirmation of data and status:

• Once the ZK proof is verified, the transaction is finalized through smart contracts.
• L1 and L2 are bridged through smart contracts to ensure the safe transfer of funds and status.

The design of Hybrid Rollups provides several significant advantages:

• Efficiency and cost-effectiveness: By using ZK proofs, Hybrid Rollups can process more transactions while consuming less gas.
• Enhanced security: Combining traditional fraud proofs and ZK proofs, the security and correctness of transactions can be guaranteed even when encountering potential malicious behavior.
• Scalability: Using recursive proofs, Hybrid Rollups can handle large-scale transactions without sacrificing performance, supporting a wider range of blockchain applications.
• Compatibility and flexibility: Supports multiple smart contracts and programming languages, allowing developers to easily migrate existing applications to Hybrid Rollups.

2.2 How zkMIPS Achieves Nice ZK Compatibility

The core idea of ​​ZK is to convert the program execution process into a mathematical proof that can be easily verified so that everyone can easily verify the correctness of the program execution without repeating the program. The difficulty lies in transforming arbitrary program logic into Relatively stable mathematical proof.

Developers usually use high-level languages ​​to develop programs, and different high-level languages ​​use different logic to “talk” to the hardware.

Therefore, the implementation paths of existing ZK projects are often incompatible with each other. Scroll directly writes circuits for each opcode of EVM, achieving opcode-level equivalence, which accurately reflects EVM, but brings a huge amount of engineering.

Polygon zkEVM creates a custom VM with optimized performance, converts EVM bytecode directly into VM bytecode, and achieves opcode-level equivalence more efficiently. However, the introduction of a large amount of custom code may lead to deviation from EVM in the long term;

zkSync created its VM (SyncVM) and defined its algebraic intermediate representation (AIR) based on registers, and then built a specialized compiler to compile Yul (an intermediate language that can be compiled into words of different EVM versions). Section code (considered as a lower-level Solidity) is compiled into LLVM-IR, and then compiled into instructions for a custom VM, thus achieving Solidity-level compatibility, but it cannot directly use existing Ethereum tools. Conversions may also require re-audit procedures.

StarkNet abandons EVM compatibility and directly uses its low-level language (Cairo) to run a custom smart contract VM (Cairo VM) to achieve ultimate ZK efficiency.

Compared to the solutions of the above projects, ZKM has chosen a more inclusive path: zkMIPS.

MIPS, which stands for “Microprocessor without Interlocked Pipeline Stages”, is a simply designed microprocessor instruction set that started in 1985.

The basic principle of MIPS is to reduce complex microprocessor instructions to their most basic form, which increases processing speed and reduces the complexity of executing programs.

In the zkMIPS system, this instruction set is used to implement the conversion of programs to ZK proofs.

The implementation process of zkMIPS is as follows:

• Program to MIPS conversion: First, smart contracts or programs written in high-level programming languages ​​such as Solidity or Rust are compiled into the MIPS instruction set. This step is about converting higher-level abstractions into concrete operations that can be performed at the hardware level.
• Generate ZK proofs: These MIPS instructions are then used to generate the corresponding zero-knowledge proofs. Due to the simplified nature of MIPS, this step is more computationally efficient and can produce proofs faster without sacrificing security.

Advantages of zkMIPS

• Compatibility: zkMIPS supports both EVM-compatible Solidity and other mainstream development languages ​​such as Rust and Move. This enables zkMIPS to serve the broader blockchain development ecosystem, bringing more application possibilities.
• Cost-effectiveness: Due to the efficiency of the MIPS instruction set, zkMIPS can significantly reduce computing costs when generating zero-knowledge proofs, increasing the overall sustainability of the system.
• Recursive proofs: zkMIPS supports recursive proofs, which aggregate multiple proofs into a more manageable unit. This is critical in improving system scalability.

The advantages of MIPS have been integrated into projects such as Optimism. Optimism’s Cannon mechanism converts executed programs into MIPS, making it easier and more efficient to find errors and re-execute when the execution process is challenged.

Metis has also followed this trend and integrated Cannon into its ecosystem. This further validates the practicality and efficiency of zkMIPS technology.

Decentralized Sequencer: Decentralization and Sustainability

In addition to using Hybrid Rollups to combine the advantages of OP and ZK, Metis also actively promotes the implementation of decentralized sequencers and sets a decentralized example for Rollups.

In the traditional Rollup model, although a single Sequencer can effectively process transactions and data, it also concentrates a great deal of power, which may lead to various risks:

• Operational risk: If the sequencer fails or is attacked, the transaction processing of the entire system will be blocked.
• Censorship risk: Sequencers can selectively process or reject transactions, which may restrict users’ access to specific decentralized finance (DeFi) protocols or services.
• Manipulation risk: In transaction sequencing, the sequencer may prioritize its transactions and obtain improper benefits by increasing transaction fees, that is, the maximum extractable value (MEV).

To solve the above problems, Metis designed a decentralized Sequencer pool. It is composed of multiple Sequencer nodes to jointly aggregate, sequence and execute transactions. This design ensures the fairness and transparency of the system:

• Consensus mechanism: More than two-thirds of Sequencer nodes must agree on the status of each new block before a transaction batch can be submitted to the Ethereum mainnet (L1).
• Multi-party computation (MPC) signature: Before the transaction batch is submitted to L1, the authenticity of the batch is verified through MPC signature to ensure the accuracy of the data.

Advantages of decentralized Sequencer:

• Enhanced security: Through joint decision-making by multiple nodes, the risk of single-point failure is reduced and the robustness and security of the network are increased.
• Reduce the possibility of censorship and manipulation: The existence of multiple Sequencers makes it difficult for a single node to manipulate or censor transactions, protecting users’ freedom of transactions.
• Stability and redundancy: The system supports the smooth rotation of Sequencers, minimizing the impact of failures or interruptions and improving the stability of the entire network.

In Metis’ decentralized Sequencer model, each node is composed of several key components:

• L2 Geth (including OP-Node): Responsible for sequencing transactions and assembling blocks.
• Adapter module: serves as an intermediary for interaction with other external modules (mainly PoS nodes).
• Batch submitter (Proposer): Responsible for constructing transaction batches and submitting them to L1 after obtaining approval from multiple Sequencers.
• PoS Node: Coordinates between Ethereum, consensus and Metis layers to ensure assets are securely locked and validators are rewarded.
• Consensus layer: Contains a group of Tendermint PoS nodes running in parallel with the Ethereum main network to ensure operational efficiency without hindering the process of the main network.

Source: https://ethresear.ch/t/pos-sequencer-pool-decentralizing-an-optimistic-rollup/16760

This design allows Metis’s decentralized Sequencer pool to not only improve the fairness and transparency of transaction processing but also enhance the security and stability of the network through decentralized power. All of them are key elements in building a trusted and sustainable blockchain ecosystem.

Summary & Outlook

Metis’ technological and conceptual advantages create a solid foundation for further development in the future. Its zkMIPS-based Hybrid Rollups is expected to solve the compatibility problem for ZK-Rollup and bring a more diverse developer ecosystem.

The advancement of decentralized Sequencer demonstrates the team’s vision of pursuing decentralization. As the Metis ecosystem continues to mature, we have reason to believe that Metis will become a dark horse that continues to run in the future L2 competition, creating a steady stream of value for users and developers.

Statement:

1. This article originally titled “Exploring Technological Advantages of Metis” is reproduced from [Biteye Community]. All copyrights belong to the original author [Wilson Lee, Biteye core contributor]. If you have any objection to the reprint, please contact the Gate Learn team, the team will handle it as soon as possible.

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