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Canton EVM Bridge - Solidity Contracts

Solidity smart contracts for the EVM side of the Canton Network bridge.

Overview

These contracts enable bidirectional token transfers between EVM chains (Ethereum, Base, etc.) and Canton Network:

  • Deposits (EVM → Canton): Users lock ERC-20 tokens in the bridge contract. The middleware detects the deposit event and mints CIP-56 tokens on Canton.
  • Withdrawals (Canton → EVM): Canton burns CIP-56 tokens. The middleware signs a withdrawal proof, and the relayer releases ERC-20 tokens on EVM.

Contracts

Core

Contract Description
CantonBridge.sol Main bridge contract with deposit/withdraw functionality
TokenRegistry.sol Registry for managing bridgeable ERC-20 tokens

Interfaces

Interface Description
ICantonBridge.sol Bridge interface with events and errors
IBridgeEvents.sol Administrative and operational events

Security

Contract Description
RateLimiter.sol Rate limiting per token per time period

Mocks

Contract Description
MockERC20.sol Mock tokens for testing (USDC, WBTC, PROMPT)

Key Features

  • Role-Based Access Control: Admin, Relayer, and Pauser roles
  • Rate Limiting: Configurable per-token rate limits
  • Reentrancy Protection: All state-changing functions protected
  • Pausable: Emergency pause functionality
  • Large Withdrawal Time Lock: Configurable delay for large withdrawals
  • Signature Verification: Withdrawals require valid relayer signature

Build

# Install dependencies
forge install

# Build contracts
forge build

# Run tests
forge test -vv

Deployment

# Set environment variables
export PRIVATE_KEY=<deployer-private-key>
export ADMIN_ADDRESS=<admin-address>
export RELAYER_ADDRESS=<relayer-address>

# Deploy to network
forge script script/Deploy.s.sol --rpc-url <rpc-url> --broadcast

Usage

Deposit (EVM → Canton)

// 1. Approve tokens
IERC20(token).approve(bridgeAddress, amount);

// 2. Deposit with Canton fingerprint
bridge.depositToCanton(token, amount, cantonRecipient);

Withdrawal (Canton → EVM)

Called by the relayer after Canton burn is confirmed:

// Relayer signs the withdrawal message
bridge.withdrawFromCanton(token, amount, recipient, withdrawalId, proof);

Security Considerations

  • Only registered tokens can be bridged
  • Withdrawals require valid signature from authorized relayer
  • Rate limits prevent drain attacks
  • Large withdrawals are time-locked
  • Emergency pause available for incidents

Events

Deposit Events

  • DepositToCanton(token, sender, amount, cantonRecipient, nonce)

Withdrawal Events

  • WithdrawalFromCanton(token, recipient, amount, cantonSender, withdrawalId)
  • WithdrawalProcessed(withdrawalId, success)

Admin Events

  • TokenRegistered(token, symbol, cantonTokenId, isNative)
  • BridgePaused(by) / BridgeUnpaused(by)
  • RateLimitSet(token, amount, period)

License

Apache 2.0