Cross-Chain Flow

Overview

Butter Network provides the infrastructure that allows transactions to move freely and securely across chains.

Core Process:

1. User initiates cross-chain request on source chain

2. Source chain Router → Bridge processing, lock/burn assets, and emit MessageOut event

3. MAP Relay Chain performs cross-chain verification and fee deduction, emit MessageRelay event

4. Target chain Bridge verifies and releases assets, emit MessageIn event

5. Receiver (optional) executes Swap or custom calls

Cross Chain Flow

1. Source Chain Processing

• Router contract serves as unified entry point

• Supports source chain Swap operations

• Bridge handles asset management and cross-chain message generation

2. MAP Relay Chain Verification

• Oracle Verification: Relay Chain uses multi-sig Oracle to verify blocks and receipts from other chains

• Fee Processing: Deduct Bridge Fee, Affiliate Fee, and Base Fee after verification

• Message Relay: Generate target chain proof and emit MessageRelay event

• Cross-chain Coordination: Coordinate verification between source and target chains

3. Target Chain Execution

• Light Client Verification: Verify MAP Relay Chain state using ZK + Light Client technology

• Asset Management: Mint/release BridgeToken based on verification results

• Message Processing: Emit MessageIn event after successful verification

• Receiver Integration: Optionally call Receiver contract for token swaps or custom interactions

Core Contract Modules

1. Router Contract

Entry point for cross-chain transactions, supports swapping user tokens to BridgeToken on the source chain before initiating cross-chain requests.

2. Bridge Contract

Responsible for sending and verifying cross-chain transactions. Locks/burns BridgeToken on the source chain and mints/releases BridgeToken on the target chain.

3. Relay Contract

Deployed on MAP Relay Chain, coordinates cross-chain verification and fee processing. Receives cross-chain requests from source chains, validates them through Oracle nodes, and generates proofs for target chains.

4. Receiver Contract

Handles Bridge Token exchange to target tokens on the target chain and supports custom contract interactions.

5. ClientNode Contract

Based on ZK + Light Client technology, used to verify MAP Relay Chain blocks and events to ensure cross-chain message validity.

6. OracleNode Contract

Based on multi-signature mechanism, used to verify blocks and events from other chains to ensure source chain transaction authenticity.

Key Roles

1. User

End users who initiate cross-chain transactions and receive assets on the target chain.

2. Maintainer

Responsible for maintaining light client updates, periodically synchronizing MAP Relay Chain epoch information to other chains.

3. Messenger

Constructs cross-chain verification proofs and submits them to target chains for execution.

4. Oracle Signer

Submits cross-chain information from other chains to the oracle node for multi-signature verification.

Fee Model

Fee Type	Purpose
Affiliate Fee	Reward for referrers who bring users
Bridge Fee	Cross-chain bridge service fee
Base Fee	Cover target chain gas execution costs

Exception Handling

• Source Chain Failure: Swap failure directly reverts, user assets are safe

• Target Chain Failure: Retry first, if retry fails then refund bridge token

• Verification Failure: No cross-chain operation executed, ensuring asset safety

Typical Use Cases

Scenario 1: Simple Cross-Chain Transfer

User → Router → Bridge → Relay Verification → Bridge → User

Scenario 2: Cross-Chain Swap

User → Router(Swap) → Bridge → Relay Verification → Bridge → Receiver(Swap) → User

Scenario 3: Cross-Chain DeFi Integration

User → Router → Bridge → Relay Verification → Bridge → Receiver(Custom Call) → DeFi Protocol

Summary

Core advantages of ButterSwap cross-chain flow:

✅ Three-Layer Architecture: Source chain processing → MAP Relay Chain verification → Target chain execution

✅ Hybrid Verification: ZK + Light Client + Oracle triple security

✅ Flexible Fee Model: Unified fee processing on Relay Chain

✅ High Extensibility: Support for Receiver contract Swap and custom calls

✅ Secure and Reliable: Multi-layer verification mechanism and comprehensive exception handling