Preface

In the rapidly developing field of blockchain technology, interoperability has become the key to achieving seamless connectivity between different blockchains. ACX (Across Protocol) is an intent-driven interoperability protocol designed to provide efficient, low-cost cross-chain transaction solutions. This protocol not only simplifies the user's transaction process but also promotes the free flow of assets between different blockchains.

What is Across Protocol?

Across Protocol is an innovative cross-chain interoperability solution designed to achieve efficient cross-chain transactions within the blockchain ecosystem. It adopts an intent-based architecture that allows users to specify the desired outcome without having to be concerned about the specific technical execution details. The system relies on a competitive relay network to ensure that these transaction objectives are achieved in the most cost-effective and fastest manner.

As a leading cross-chain bridge in terms of average monthly trading volume, Across Protocol relies on its advanced architecture to provide fast and cost-effective transaction experiences while ensuring security, bringing users a high-quality experience. The design goal of this protocol is to simplify cross-chain interaction and solve the fragmentation problem faced by developers and users in the current multi-chain environment, thereby improving the collaborative efficiency of the entire blockchain ecosystem.

Core Team Members

The core development team behind Across Protocol is also the development team for the synthetic asset protocol UMA (Risk Labs), and Across and UMA can be understood as two products of the same team.

• Hart Lambur | Co-founder of Across Protocol & UMA
• Melissa Quinn | COO of Across Protocol & UMA
• Matthew Rice｜Across Protocol & UMA CTO

Technical architecture

When users submit asset transfer orders to Across, such as transferring assets from Chain A to Chain B, they deposit funds into the Spoke Pool on Chain A and provide instructions on where they want the funds to go and the required fees. The relayer examines these deposits, verifies the details, and immediately provides the funds to users on Chain B.

After completing the relay, the relayer submits the proof of the operation and the validity of the original deposit to the Optimistic Oracle (OO). Once verified by OO, the relayer can receive compensation. The compensation comes from the Hub Pool liquidity pool on the Ethereum mainnet, which is funded by liquidity providers (LP). Liquidity providers can also earn fees based on the amount of user deposits in each transfer.

The rules for transferring funds between the Spoke Pool on L2 and the Hub Pool on L1 are detailed in UMIP-157. Anyone wishing to transfer funds between the pools must submit valid proof that complies with UMIP rules to OO.

To understand how all of this comes together, please refer to the diagram below, which illustrates the complete end-to-end process.

(Source:https://docs.across.to/user-docs/how-across-works/overview）

Ecological System Roles

Using Across Protocol for cross-chain transactions involves several roles:

1. User
   Users are individuals who bridge assets between Layer 2 (L2) and Layer 1 (L1) through Across. They pay fees to relayers and liquidity providers to quickly transfer tokens to the target chain. Users enjoy convenient cross-chain asset services through the Across platform.

1. Relay
   Relayers provide short-term token loans to users, charging a certain fee. When a user requests a deposit, the relayer provides the required tokens on the target chain, deducts the relevant fees, and then sends the funds to the recipient. Relayers bear the cost of capital, gas fees, software risks, and finality risks, and receive compensation for these risks. Anyone with the technical ability can operate relayer software or develop their own relayer software.

1. Liquidity Provider (LP)
   Liquidity providers deposit assets into Across's liquidity pool, allowing relayers to flexibly choose where to obtain refunds. Liquidity providers earn fee income by providing funds, while bearing capital costs and liquidity risks. The liquidity pool ensures that asset transfers can be completed even if relayers cannot quickly fill deposits.

1. Data worker
   Data workers support the stability of the Across system, responsible for submitting bundled packages to move system assets across the network. They are required to submit a deposit, and anyone can dispute invalid bundled packages and receive a dispute reward. Each bundled package contains relay refunds, token transfers, and slow fill instructions, which are summarized through Merkle roots to ensure the efficient operation of the Across system.

Cross-chain Process

By using the Across Protocol for cross-chain transfers, users can typically receive coins on the target chain within 1-4 minutes. This is mainly provided by relayers, and the subsequent real fund transfers, Optimistic challenge period, etc. are unrelated to the users, with the risks mainly borne by the relayers.

1. The user initiates a cross-chain request to transfer XX coins from Chain A to Chain B
2. Users deposit coins on Chain A into the Across Protocol smart contract or liquidity pool.
3. The relayer in the B chain gives XX coins to the user (minus the relaying fee)
4. Relayer submits relevant proofs to Across Protocol
5. If the process is uncontroversial, the liquidity pool pays XX coins to the relayer (minus protocol fees)
6. In case of any disputes, submit to the Optimistic Oracle for resolution.
7. The above is an instant channel, mainly completed through the relay, but if there is no relay to take over this order, the user's coins on Chain A can still be transferred to Chain B through the slow channel. The slow channel is slower, but users can still meet the demand of receiving coins on Chain B.

Token Economics

Cross-protocol token $ACX is an ERC-20 token launched in November 2022, allowing for decentralized ownership and protocol control. Its main purpose is for governance participation and as a liquidity incentive token. The total supply limit is 1 billion tokens, distributed as follows:

• Early airdrop 115 million
• Strategic Partnership & Financing of 250 million (including the previously mentioned financing and swap of UMA tokens with Risk Labs treasury)
• Protocol LP rewards 1 billion
• Across DAO reserves 5.35 billion

Token Usage

Its main functions include incentivizing liquidity providers, expanding the community, and strengthening its position as a leading Layer 2 bridge, ACX's token economics strategy involves initial distribution and reward locking incentive plans, aimed at promoting long-term participation and reducing short-term speculation.

Risk Warning

According to CoinGecko data before the deadline (2024/1/7), ACX has fallen by approximately 70% since reaching a new high of 1.8 blocks.

Gate.io spot has listed ACX, trade now:https://www.gate.io/en/trade/ACX_USDT

ERC-7683 Cross-Chain Intent Standard

Proposed jointly by Uniswap Labs and Across Protocol, this is a cross-chain intention standard on Ethereum that can provide a unified order structure and API standard for all cross-chain intentions, which can improve the problem of the current cross-chain format and standards being too chaotic.

ERC-7683 unifies the Ethereum ecosystem and reduces friction in cross-chain activities, supporting seamless interoperability between the Ethereum mainnet, L2 chains, aggregators, application chains, and side chains in an accessible, scalable, and secure manner. It meets the demand for consistent cross-chain functionality, making it easier for developers to build and allowing users to interact across these networks more easily, such as token exchanges, NFT transfers, and cross-chain deposits. Developers can access standardized APIs, reducing integration costs and achieving greater liquidity access.

Currently, more than 40 projects have committed to supporting ERC-7683. With the adoption of this standard, it will help builders create a unified, scalable Ethereum ecosystem and may impact interoperability between other blockchains.

Summary

As an innovative cross-chain interoperability solution, Across Protocol (ACX) provides users with efficient and low-cost cross-chain transaction experience through its intent-based architecture and competitive relay network. It not only simplifies users' transaction process but also promotes the free flow of assets between different blockchains, solving the fragmentation problem faced by developers and users in a multi-chain environment. With the introduction and adoption of the ERC-7683 cross-chain intent standard, Across Protocol is expected to further promote seamless interoperability within the Ethereum ecosystem, providing a broader space for the development and application of blockchain technology.