Detailed explanation of the advantages and challenges of the decentralized Metis sorter

What is Metis, the Layer2 network that has recently seen a rapid increase in on-chain funds? It seizes the centralization issue in Rollups by building a peer-to-peer network of sequencers and a staking consensus mechanism, achieving the first decentralized sequencer and attracting market attention successfully.

This article is not investment advice.

Introduction to Metis

Metis is a general Layer2 network in the Ethereum ecosystem that was launched in May 2021 and launched its mainnet, Andromeda, in November of the same year.

Metis Andromeda features include its virtual machine MVM achieving EVM Equivalence, early completion of the decentralized sequencer, and other unique aspects in the current mainstream Layer2 competition. Metis was initially designed as a hard fork network of Optimism, but with Optimism gaining control over the decentralized sequencer, Metis attempted to pave its own path from the beginning by focusing on a decentralized sequencer direction.

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Metis Becomes a Market Hotspot

Rapid Growth of On-chain Funds

Recently, the TVL of Metis on-chain funds has grown rapidly. Starting from $100 million on the 20th of this month, it quickly rose to a historical high of $720 million, currently ranking third among all Ethereum ecosystem Layer2 networks.

Token Price

The project's token is named METIS, used to pay for Metis Andromeda on-chain gas fees and stake to operate the sequencer. The METIS token has surged by approximately 350% this month, reaching around $84 at the time of writing, with a circulating market cap of about $340 million.

Metis Technical Architecture

When researching blockchain technical architecture, you can generally approach it from three aspects: decentralized ledger, consensus mechanism, and virtual machine. Rollups typically also need to consider their transaction proof verification mechanism, such as the differences between optimistic proof and zero-knowledge proof.

Decentralized Ledger: Off-chain Storage

Metis inherits the Optimistic Rollups architecture, where its database primarily consists of two parts of smart contracts:

• Canonical Transaction Chain CTC: stores complete transaction information to differentiate the order of transactions.
• State Commitment Chain SCT: records the computed transaction states.

However, to reduce the technical feasibility of a decentralized sequencer and lower the on-chain cost of transaction data, Metis stores complete transaction information on the IPFS system outside the Ethereum mainnet.

Consensus Mechanism: Decentralized Sequencer

Metis Andromeda's consensus layer differs from Optimistic Rollups by introducing a peer-to-peer network transmission structure and using Proof of Stake (PoS) to ensure the normal operation of the sequencer, allowing the network to accommodate multiple sequencers simultaneously for decentralization. Metis's consensus technology stack mainly includes three roles: Sequencer, proposers, and verifiers.

Any transaction information on the Metis network goes through the sequencer for transaction ordering and execution, with proposers uploading the results to the Ethereum mainnet. To ensure the normal operation of the sequencer, the ecosystem also has verifiers responsible for monitoring the correctness of transaction results. If abnormalities are found, the sequencer will be penalized, strengthening the existing fraud-proof mechanism.

Proof Mechanism: ZKFP

Currently, the two mainstream proof mechanisms for Rollups—fraud-proof and zero-knowledge proof (ZKP)—each have their drawbacks. Fraud-proof requires a lock-up period, usually taking a week to ensure transaction finality, which is unfriendly for user experience. While ZKP can provide quick finality, the computational power required for the proof mechanism is larger, leading to hardware upgrades for Layer2 nodes and sequencers, hindering decentralization. Additionally, the development difficulty of zkEVM is high, making it challenging to achieve EVM equivalence.

Metis integrates the benefits of both proof mechanisms and introduced the Hybrid Rollup Zero Knowledge fraud-proof (ZKFP) in March this year.

By assuming all transactions are valid to improve transaction processing speed and then using zero-knowledge proof to verify transaction finality, if anomalies occur, fraud-proof is proposed. This approach enhances transaction speed through the Optimistic Rollups architecture and uses Zero-Knowledge Rollups to enhance transaction finality and security. The integration of both mechanisms provides the following benefits:

• EVM Equivalence: Provides EVM equivalence through the Optimistic architecture.
• Security: Enhanced security through zero-knowledge proof verification.
• Rapid Finality: Reduces the fraud-proof lock-up period from seven days to four hours.

Virtual Machine: EVM Equivalence

Metis inherits the Optimistic Rollup design and creates a specialized EVM-equivalent virtual machine, Metis Virtual Machine (MVM). The MVM design is almost identical to EVM, allowing the use of existing tools and services in the Ethereum ecosystem. However, due to network design requirements mentioned above, two differences arise:

Native IPFS Invocation Function: As previously explained, Metis separates computation and storage due to the decentralized sequencer design, storing complete transaction information on IPFS outside the Ethereum mainnet. The MVM can integrate with the IPFS resolver function to provide developers with an out-of-the-box data storage package.

Verification Mechanism: Another feature of MVM is the anti-fraud contract—MVM_Verifier, providing verifier operation. Its main function is to manage fraud-proof verification processes. When the anti-fraud contract is verified, the contract can remove specific states from SCT. This is usually for abnormal transactions.

Furthermore, MVM uses WASM and MIPS to establish a more universal execution environment for zero-knowledge proof to be more practical. By writing programs in low-level languages to build a solid foundation, it can be used across different networks and systems with minimal modifications.

Decentralized Sequencer Narrative in the Crypto Market

In order to provide a decentralized sequencer system, Metis Andromeda not only utilizes the well-established Proof of Stake but also brings many interesting innovations, such as integrating IPFS functionality with the virtual machine for off-chain storage of transaction information to overcome the limitations of multi-sequencer technology, or incorporating verifiers and ZKFP proof mechanisms to enhance the fraud-proof security of decentralized sequencers. Compared to existing Rollups, Metis further promotes decentralization of the network and has indeed achieved it.

With Layer2 projects receiving widespread market attention recently, although they face market issues of lacking substantial ecosystems, the narrative of "decentralization" is fundamental in the Web3 ecosystem. Different from Arbitrum or Optimistic's control over the sequencer, Metis's approach to "truly decentralized sequencers" does bring imagination to the market.

Metis should also consider the advantages beyond decentralized sequencers. However, it should not forget about mainstream Rollups. If they open up decentralized sequencers, whether Metis's advantages can be sustained remains to be seen and verified by the market.

This article is not investment advice.