fisherBridgeSend

Function Type: external
Function Signature: fisherBridgeSend(address,address,address,uint256,uint256,bytes)
Access Control: onlyFisherExecutor
Returns: void

Processes Fisher bridge token transfers from host to external chain. Validates balance and signature, deducts from sender, pays executor fee, and emits event for external chain processing.

Parameters

Parameter	Type	Description
from	address	User initiating the withdrawal from EVVM
addressToReceive	address	Recipient address on the external chain
tokenAddress	address	Token contract address or address(0) for native coin
priorityFee	uint256	Fee amount paid to the fisher executor
amount	uint256	Amount to withdraw from user's EVVM balance
signature	bytes	Cryptographic signature (EIP-191) from the from address authorizing this withdrawal.

Access Control

modifier onlyFisherExecutor() {
    if (msg.sender != fisherExecutor.current) {
        revert();
    }
    _;
}

Only addresses with the current fisherExecutor role can call this function.

Workflow

1. Principal Token Protection

if (tokenAddress == core.getEvvmMetadata().principalTokenAddress)
    revert Error.PrincipalTokenIsNotWithdrawable();

Prevents withdrawal of Principal Token (MATE) to protect ecosystem integrity.

2. Balance Validation

if (core.getBalance(from, tokenAddress) < amount)
    revert Error.InsufficientBalance();

Verifies user has sufficient EVVM balance for the withdrawal amount (note: priority fee is deducted separately).

3. Signature Verification

core.validateAndConsumeNonce(
    from,
    Hash.hashDataForFisherBridge(
        addressToReceive,
        tokenAddress,
        priorityFee,
        amount
    ),
    fisherExecutor.current,
    nonce,
    true,
    signature
);

Validates EIP-191 signature using Core contract's nonce system. The hash is generated using TreasuryCrossChainHashUtils.hashDataForFisherBridge() with the transaction parameters. The async: true parameter indicates this uses a separate nonce system from regular EVVM operations.

4. EVVM Balance Operations

User Balance Deduction

core.removeAmountFromUser(from, tokenAddress, amount + priorityFee);

Deducts total amount (transfer + fee) from user's EVVM balance.

Fisher Executor Fee

if (priorityFee > 0)
    core.addAmountToUser(msg.sender, tokenAddress, priorityFee);

Credits priority fee to Fisher executor's EVVM balance as processing incentive.

5. Event Emission

emit FisherBridgeSend(
    from,
    addressToReceive,
    tokenAddress,
    priorityFee,
    amount,
    nonce
);

Emits an event containing all transfer details for external chain monitoring and processing.

Event Definition

event FisherBridgeSend(
    address indexed from,
    address indexed addressToReceive,
    address indexed tokenAddress,
    uint256 priorityFee,
    uint256 amount,
    uint256 nonce
);

Event Parameters

• from: User who initiated the withdrawal (indexed)
• addressToReceive: Recipient on external chain (indexed)
• tokenAddress: Token being withdrawn (indexed)
• priorityFee: Fee paid to fisher executor
• amount: Withdrawal amount
• nonce: Execution nonce used for this transaction

External Chain Processing

The emitted event serves as a signal for external chain operations. The corresponding external chain station or fisher services should:

1. Monitor for FisherBridgeSend events
2. Extract transfer details from event parameters
3. Execute the actual token transfer on the external chain
4. Transfer amount of tokenAddress to addressToReceive

Security Features

Signature Security

• EIP-191 Compliance: Standard Ethereum signed message format
• Nonce Protection: Prevents signature replay attacks
• User Authorization: Cryptographic proof of user consent

Balance Protection

• Principal Token Guard: Prevents withdrawal of ecosystem's core token
• Sufficient Balance Check: Validates user has adequate funds
• Atomic Operations: Balance updates are processed atomically

Access Control

• Fisher Authorization: Only current fisher executor can initiate withdrawals
• Signature Validation: Requires valid user signature for each transaction (see signature format)

Fee Structure

The priority fee mechanism incentivizes fisher executors:

• User Pays: Total debit of amount + priorityFee from user balance
• Fisher Receives: Priority fee credited to executor's EVVM balance
• Net Transfer: User receives amount on external chain

Error Conditions

Error	Condition
PrincipalTokenIsNotWithdrawable()	Attempting to withdraw principal token
InsufficientBalance()	User lacks sufficient EVVM balance
InvalidSignature()	Signature verification fails
Access Control Revert	Called by unauthorized address

Usage Flow

1. User Intent: User wants to withdraw tokens from EVVM to external chain
2. Signature Creation: User signs withdrawal authorization message
3. Fisher Execution: Authorized fisher calls fisherBridgeSend with signature
4. Validation: Function validates signature and user balance
5. Balance Update: EVVM balances updated (user debited, fisher credited fee)
6. Event Emission: Event emitted for external chain processing
7. External Transfer: External services process the actual token transfer

Off-chain Coordination Required

This function only updates EVVM balances and emits events. The actual token transfer on the external chain must be handled by off-chain services monitoring these events.