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Overview

TokenMinterV2 is responsible for minting and burning tokens on the local domain. It inherits from the V1 TokenMinter contract and adds support for minting to multiple recipients in a single transaction, enabling efficient fee distribution. Contract Location: src/v2/TokenMinterV2.sol

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Key Features

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New Features vs V1

  1. Multi-Recipient Minting: Mint to two recipients in a single transaction (useful for separating fees)
  2. Efficient Fee Distribution: Mint principal amount to recipient and fee to fee recipient atomically
  3. Backward Compatible: Inherits all V1 functionality for single-recipient minting

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Constructor

constructor(address _tokenController)

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Parameters

  • _tokenController (address): Token controller address

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Core Functions

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mint (Multi-Recipient)

function mint(
    uint32 sourceDomain,
    bytes32 burnToken,
    address recipientOne,
    address recipientTwo,
    uint256 amountOne,
    uint256 amountTwo
) external returns (address)
Mints to multiple recipients amounts of local tokens corresponding to the given (sourceDomain, burnToken) pair. Reference: src/v2/TokenMinterV2.sol:54

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Parameters

  • sourceDomain (uint32): Source domain where burnToken was burned
  • burnToken (bytes32): Burned token address as bytes32
  • recipientOne (address): Address to receive amountOne of minted tokens
  • recipientTwo (address): Address to receive amountTwo of minted tokens
  • amountOne (uint256): Amount of tokens to mint to recipientOne
  • amountTwo (uint256): Amount of tokens to mint to recipientTwo

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Returns

  • mintToken (address): Address of the token that was minted

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Requirements

  • Contract must not be paused
  • Caller must be the local TokenMessenger
  • The (sourceDomain, burnToken) pair must map to a nonzero local token address
  • Both mint operations must succeed

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Behavior

This function performs two sequential mint operations:
  1. Mints amountOne to recipientOne
  2. Mints amountTwo to recipientTwo
If either mint operation fails, the entire transaction reverts.

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Inherited Functions

From TokenMinter (V1):

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mint (Single-Recipient)

function mint(
    uint32 sourceDomain,
    bytes32 burnToken,
    address to,
    uint256 amount
) external returns (address mintToken)
Mints amount of local tokens corresponding to the given (sourceDomain, burnToken) pair, to to address. Reference: src/TokenMinter.sol:85

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Parameters

  • sourceDomain (uint32): Source domain where burnToken was burned
  • burnToken (bytes32): Burned token address as bytes32
  • to (address): Address to receive minted tokens
  • amount (uint256): Amount of tokens to mint

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Returns

  • mintToken (address): Token that was minted

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burn

function burn(address burnToken, uint256 burnAmount) external
Burns tokens owned by this TokenMinter. Reference: src/TokenMinter.sol:111

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Parameters

  • burnToken (address): Burnable token address
  • burnAmount (uint256): Amount of tokens to burn (must be greater than 0 and less than or equal to maximum burn amount per message)

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Requirements

  • Contract must not be paused
  • Caller must be the local TokenMessenger
  • Burn amount must be within the burn limit for the token

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Token Controller Functions

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linkTokenPair

function linkTokenPair(
    address localToken,
    uint32 remoteDomain,
    bytes32 remoteToken
) external
Links a local token to a remote token (token controller only).

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unlinkTokenPair

function unlinkTokenPair(
    address localToken,
    uint32 remoteDomain,
    bytes32 remoteToken
) external
Unlinks a local token from a remote token (token controller only).

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setMaxBurnAmountPerMessage

function setMaxBurnAmountPerMessage(
    address localToken,
    uint256 burnLimitPerMessage
) external
Sets the maximum burn amount per message for a local token (token controller only).

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getLocalToken

function getLocalToken(
    uint32 remoteDomain,
    bytes32 remoteToken
) external view returns (address)
Gets the local token address associated with the given remote domain and token.

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Local TokenMessenger Management

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addLocalTokenMessenger

function addLocalTokenMessenger(address newLocalTokenMessenger) external
Adds a TokenMessenger for the local domain (owner only). Only this TokenMessenger has permission to call mint() and burn() on this TokenMinter. Reference: src/TokenMinter.sol:128

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removeLocalTokenMessenger

function removeLocalTokenMessenger() external
Removes the TokenMessenger for the local domain (owner only). Reference: src/TokenMinter.sol:151

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setTokenController

function setTokenController(address newTokenController) external
Sets the token controller address (owner only). Reference: src/TokenMinter.sol:168

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State Variables

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Inherited from TokenMinter

  • localTokenMessenger (address): Local TokenMessenger with permission to call mint and burn
  • tokenController (address): Token controller address (inherited from TokenController)

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Inherited from TokenController

  • burnLimitsPerMessage (mapping): Per-token burn limits
  • remoteTokensToLocalTokens (mapping): Remote token to local token mappings

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Integration Example

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Multi-Recipient Mint (V2)

// TokenMessenger calls TokenMinter to mint tokens and fees
address mintedToken = tokenMinter.mint(
    sourceDomain,
    burnToken,
    recipient,      // Main recipient
    feeRecipient,   // Fee recipient
    950000,         // 0.95 USDC to recipient
    50000           // 0.05 USDC fee to fee recipient
);

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Single-Recipient Mint (V1 Compatibility)

// Traditional single-recipient mint
address mintedToken = tokenMinter.mint(
    sourceDomain,
    burnToken,
    recipient,
    1000000 // Full 1 USDC to recipient
);

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Burn Tokens

// TokenMessenger calls TokenMinter to burn tokens
tokenMinter.burn(
    address(usdc),
    1000000 // 1 USDC
);

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Differences from V1

| Feature | V1 | V2 | |---------|----|----|| | Single-recipient mint | ✓ | ✓ (inherited) | | Multi-recipient mint | ✗ | ✓ | | Burn functionality | ✓ | ✓ (inherited) | | Token controller | ✓ | ✓ (inherited) | | Burn limits | ✓ | ✓ (inherited) |

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Multi-Recipient Use Cases

  1. Fee Distribution: Mint principal to recipient and fee to protocol in one transaction
  2. Gas Optimization: Reduce gas costs by combining multiple mints
  3. Atomic Operations: Ensure both mints succeed or both fail
  4. Simplified Logic: Remove need for TokenMessenger to call mint twice

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Function Signatures

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V2 Multi-Recipient Mint

mint(uint32,bytes32,address,address,uint256,uint256)

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V1 Single-Recipient Mint

mint(uint32,bytes32,address,uint256)
Both functions have the same name but different signatures, allowing the TokenMessenger to choose which to call based on whether fees need to be distributed.

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Security Considerations

  1. Burn Limit Controls: Enhanced burn limit enforcement prevents excessive burns per message
  2. Permission System: Only the registered local TokenMessenger can mint or burn
  3. Token Pairing: Strict token pairing validation ensures correct cross-chain token mappings
  4. Atomic Minting: Multi-recipient minting is atomic - both mints succeed or both fail
  5. Access Control: Token controller, owner, and pauser roles enforce proper authorization

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