Ethereum Interop Layer: Unifying Layer-2 Solutions for Enhanced User Experience

Introduction to Ethereum Interop Layer (EIL)

Ethereum has successfully addressed scalability challenges over the years by deploying multiple Layer-2 (L2) solutions such as Arbitrum, Optimism, and Base. These solutions have led to reduced transaction costs and increased efficiency. However, a new challenge has emerged: fragmentation of the user experience. Each L2 network operates as an isolated island, and users face complex steps, different bridging protocols, and complicated asset and gas management when attempting to cross-chain.

To address this pain point, the Ethereum core team recently proposed the Ethereum Interop Layer (EIL). To understand EIL, one must first revisit its foundation—ERC-4337.

ERC-4337: The Foundation for EIL

ERC-4337 is an account abstraction standard proposed for Ethereum. It does not require any modifications to the underlying Ethereum protocol. Instead, it implements smart accounts through deployed smart contracts. These accounts support advanced functionalities such as social recovery, multi-signatures, and batch operations. They also support gas payments using ERC-20 tokens via smart contracts.

Despite the technical innovations offered by ERC-4337, its actual adoption remains limited. User experience fragmentation, multi-chain coordination difficulties, high gas costs, and ecosystem compatibility issues have all constrained the widespread adoption of 4337. EIL aims to address these issues by building upon ERC-4337.

How Does EIL Work?

EIL is a set of multi-chain interoperability protocols stacked on top of the ERC-4337 framework. It extends account abstraction from a single chain to multi-chain account interoperability, enabling a seamless experience across multiple L2 networks. Specifically, EIL achieves two significant innovations:

1. Single Signature for Multi-Chain Operations (Batch Authorization): Allows users to authorize multiple operations across multiple L2 networks with a single signature. In practice, wallets first construct their respective UserOperations on each relevant chain. These operations are then aggregated into a Merkle tree. Users only need to sign the root of the tree once. When the smart account on each chain verifies the received UserOperation, it only needs to verify that it belongs to the Merkle tree and that the signature is valid. It can then execute the operation. This significantly simplifies the cross-chain operation process for users.
2. Auction-Based Cross-Chain Liquidity Provision Mechanism (XLP): Introduces a role called the Cross-Chain Liquidity Provider (XLP). The XLP takes responsibility for providing asset transfer and gas payment services across different chains. When a user locks assets on the source chain and submits a cross-chain request, multiple XLPs can bid on-chain to win the request. The winning XLP will provide a voucher for the cross-chain asset transfer, allowing the user to directly obtain funds and gas payment on the target chain to complete the required cross-chain operation. After the transaction is completed, the XLP will claim the assets that the user previously locked on the source chain.

Safety and Integrity

To ensure safety and integrity, XLPs must stake assets on the Ethereum mainnet (L1) and be subject to a rigorous dispute arbitration mechanism. If an XLP violates the rules, the staked assets will be forfeited, ensuring their integrity through economic incentives.

Implementation and Infrastructure

It's important to note that EIL does not require any changes to the consensus protocols of the Ethereum mainnet or L2 networks. All implementation relies on smart contracts and the existing ERC-4337 account abstraction framework. This design not only reduces the difficulty of implementation but also significantly reduces the potential security risks that the chains themselves may face. However, this design shifts the pressure and complexity to wallets and off-chain infrastructure.

Wallets need to support complex multi-chain transaction construction, single signature verification for multi-chain operations, interaction mechanisms with CrossChainPaymaster and XLP, and provide a simple and user-friendly user interface. Off-chain infrastructure needs to build a robust auction market, monitor XLP fund flows, and manage risk in real-time.

Conclusion

Ultimately, EIL provides users with an experience similar to that of a single chain. In the future, when users open a wallet that supports EIL, they will no longer need to frequently switch chains, manage cross-chain assets, or endure long cross-chain waiting times and complex operations. All complex cross-chain details will be automatically completed out of the user's sight. The user experience of the entire Ethereum L2 ecosystem will be gradually unified, truly realizing the vision of multi-chain integration and seamless interoperability.

EIL also opens up new possibilities for the entire Ethereum ecosystem. It not only solves the cross-chain user experience problem, but more importantly, it truly allows multiple L2 networks to "become one" in a safe, decentralized, and trustless manner.