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Crosschain Treasury Introduction

The Crosschain Treasury enables secure asset transfers between EVVM and external blockchains. This multi-chain solution uses interoperability protocols to coordinate asset management across different blockchain networks.

Architecture​

The system uses two coordinated stations that communicate through multiple cross-chain protocols:

Host Chain Station (TreasuryHostChainStation)​

  • Operates on the same blockchain as EVVM
  • Handles withdrawals from EVVM balances to external chains
  • Receives Fisher bridge deposits from external chains
  • Manages EVVM balance integration and updates
  • Integrates with EVVM core contract for balance operations

External Chain Station (TreasuryExternalChainStation)​

  • Deployed on external blockchains where user assets exist
  • Handles deposits from users to EVVM ecosystem
  • Receives Fisher bridge withdrawals from EVVM
  • Manages real asset custody (ERC20 tokens and native coins)
  • Provides deposit interfaces for multiple asset types

Supported Protocols​

ProtocolIDDescription
Hyperlane0x01Modular interoperability framework
LayerZero0x02Omnichain protocol
Axelar0x03Decentralized cross-chain network

Fisher Bridge System​

Advanced feature enabling gasless cross-chain transactions:

  • Gasless Operations: Users don't need native tokens for gas on destination chains
  • EIP-191 Signature Authorization: Users sign structured messages to authorize transfers
  • Priority Fees: Economic incentives for Fisher executors who process transactions
  • Fisher Executor Control: Permissioned addresses with onlyFisherExecutor modifier
  • Nonce-Based Security: Replay attack prevention with sequential nonce tracking
  • EVVM ID Integration: Cross-instance security through unique EVVM identifiers

When to Use Crosschain Treasury​

Ideal for:

  • EVVM on different blockchain than user assets
  • Multi-chain support requirements
  • Advanced features like gasless transactions
  • Interoperability protocol integration

Available Functions​

Host Chain Station​

External Chain Station​

Cross-Chain Flow​

External Chain          Host Chain
     │                      │
User Assets  ──────→  EVVM Balances
     │                      │ 
External Station ←──→ Host Station

The stations coordinate through cross-chain messaging to maintain synchronized asset management.

Available Functions​

Host Chain Station Functions​

External Chain Station Functions​

Supporting Libraries​

For Fisher Bridge signature requirements and verification, see the Fisher Bridge Signature Structure documentation.

The Treasury Crosschain system implements standardized error handling and data structures for cross-chain operations.

Security Features​

Security Considerations
  • Principal Token Protection: Principal token (MATE) withdrawals blocked via PrincipalTokenIsNotWithdrawable error
  • Cross-Chain Authorization: All messages require sender and chain ID validation
  • Fisher Bridge Signatures: EIP-191 compliant signatures with structured message format
  • Nonce-Based Protection: Sequential nonce tracking prevents replay attacks
  • Time-Delayed Governance: 1-day delays for admin and Fisher executor changes
  • Access Control: onlyAdmin and onlyFisherExecutor modifiers restrict critical functions
  • Protocol Validation: Chain-specific authorization for Hyperlane, LayerZero, and Axelar
  • Balance Verification: Insufficient balance checks with InsufficientBalance error protection

Gas Management​

Each protocol requires different gas payment mechanisms:

  • Hyperlane: Native tokens paid to mailbox contract
  • LayerZero: Estimated fees through LayerZero endpoint
  • Axelar: Gas service payments for cross-chain execution

Users must provide sufficient native tokens to cover cross-chain transaction costs when initiating transfers.