fisherBridgeSendCoin

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

Facilitates native coin deposits from external chain to EVVM through the fisher bridge system. This function validates user signatures using asyncNonce system, accepts native currency payments, and emits events for cross-chain processing coordination.

Parameters

Parameter	Type	Description
from	address	User initiating the deposit from external chain
addressToReceive	address	Recipient address for EVVM balance credit
priorityFee	uint256	Fee amount paid to the fisher executor
amount	uint256	Amount of native coins to deposit to EVVM
nonce	uint256	User-managed sequential nonce for replay protection
signature	bytes	Cryptographic signature (EIP-191) from the from address authorizing this deposit.

Access Control

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

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

Workflow

1. Nonce Validation

if (asyncNonce[from][nonce]) revert CoreError.AsyncNonceAlreadyUsed();

Checks if nonce has already been used. The External Chain Station uses asyncNonce[from][nonce] mapping instead of Core.sol's nonce system.

2. Signature Verification

if (
    SignatureRecover.recoverSigner(
        AdvancedStrings.buildSignaturePayload(
            evvmID,
            hostChainAddress.currentAddress,
            Hash.hashDataForFisherBridge(
                addressToReceive,
                address(0), // Native coins
                priorityFee,
                amount
            ),
            fisherExecutor.current,
            nonce,
            true
        ),
        signature
    ) != from
) revert CoreError.InvalidSignature();

Validates EIP-191 signature by recovering the signer and comparing to from address. Uses SignatureRecover.recoverSigner() with payload built by AdvancedStrings.buildSignaturePayload().

info

For more information about the signature structure, refer to the Fisher Bridge Signature Structure.

3. Payment Validation

if (msg.value != amount + priorityFee)
    revert Error.InsufficientBalance();

Ensures the fisher executor sends exactly the required amount:

• amount: Native coins for deposit to EVVM
• priorityFee: Fee paid to the fisher executor

4. Mark Nonce as Used

asyncNonce[from][nonce] = true;

Marks this nonce as consumed to prevent replay attacks.

5. Event Emission

emit FisherBridgeSend(
    from,
    addressToReceive,
    address(0), // Native coins
    priorityFee,
    amount,
    nonce
);

Emits event with transfer details for cross-chain coordination.

Native Coin Handling

Payment Structure

The msg.value must equal the sum of:

• Deposit Amount: Native coins to be credited in EVVM
• Priority Fee: Compensation for the fisher executor

Value Validation

Total Required = amount + priorityFee
msg.value must equal Total Required

Unlike ERC20 deposits, native coin deposits require exact payment matching.

Event Definition

event FisherBridgeSend(
    address indexed from,
    address indexed addressToReceive,
    address indexed tokenAddress, // address(0) for native coins
    uint256 priorityFee,
    uint256 amount,
    uint256 nonce
);

Event Parameters

• from: User who authorized the deposit (indexed)
• addressToReceive: Recipient on EVVM (indexed)
• tokenAddress: address(0) for native coins (indexed)
• priorityFee: Fee paid to fisher executor
• amount: Native coin deposit amount
• nonce: Execution nonce used for this transaction

Cross-Chain Processing

Host Chain Coordination

1. Event Monitoring: Host chain services monitor for FisherBridgeSend events with tokenAddress == address(0)
2. Native Coin Recognition: Identify native coin deposits by zero address
3. EVVM Credit: Host chain station credits addressToReceive with amount of native coins
4. Fee Handling: Priority fee management through EVVM balance system

Signature Consistency

The signature format includes address(0) for native coins, ensuring consistency between external and host chain validation.

Fisher Bridge Benefits

For Users

• Gasless Deposits: Users don't pay gas fees on external chain
• Direct Payment: Simple native currency payment to fisher
• Signature Authorization: Single signature authorizes the deposit

For Fisher Executors

• Priority Fees: Earn fees in native currency
• Direct Payment: Receive both deposit and fee in single transaction
• Service Revenue: Generate income from cross-chain deposit facilitation

Security Features

Signature Security

• EIP-191 Standard: Uses Ethereum's signed message standard (see signature format)
• SignatureRecover: Uses SignatureRecover.recoverSigner() to validate signatures
• AdvancedStrings: Payload built with AdvancedStrings.buildSignaturePayload()
• Native Coin Identifier: address(0) clearly identifies native coin deposits
• Replay Protection: asyncNonce mapping prevents signature reuse
• Parameter Binding: Signature tied to specific deposit parameters

Payment Security

• Exact Value Matching: Requires precise payment amount
• Atomic Operation: Payment and validation in single transaction
• Fee Transparency: Clear separation of deposit amount and priority fee

Access Control

• Fisher Authorization: Only authorized executors can accept deposits
• Signature Validation: Cryptographic proof of user consent required (see signature format)

Error Conditions

Error	Condition
CoreError.AsyncNonceAlreadyUsed()	Nonce has already been used for this user
CoreError.InvalidSignature()	Signature verification fails
Error.InsufficientBalance()	msg.value != amount + priorityFee
Access Control Revert	Called by unauthorized address

Usage Flow

1. User Intent: User wants to deposit native coins to EVVM
2. Signature Creation: User signs authorization message with deposit details
3. Fisher Payment: Fisher sends amount + priorityFee in native currency
4. Fisher Execution: Fisher calls fisherBridgeSendCoin with signature
5. Validation: Function validates signature and payment amount
6. Event Emission: Event emitted for cross-chain coordination
7. Cross-Chain: Host chain services process the deposit to EVVM
8. Balance Credit: Recipient receives native coins in EVVM balance

Payment Example

For a deposit of 1 ETH with 0.01 ETH priority fee:

fisherBridgeSendCoin{value: 1.01 ether}(
    userAddress,
    recipientAddress, 
    0.01 ether, // priorityFee
    1 ether,    // amount
    userNonce,  // nonce
    signature
);

Result:

• External Station: Receives 1.01 ETH
• EVVM Credit: Recipient gets 1 ETH balance
• Fisher Fee: 0.01 ETH compensation

Integration Requirements

Off-Chain Services

• Event Monitoring: Listen for FisherBridgeSend events with address(0)
• Native Coin Processing: Handle native currency cross-chain transfers
• Nonce Synchronization: Maintain coordination with host chain

Payment Coordination

• User-Fisher Agreement: Establish terms for deposit and fee amounts
• Payment Verification: Ensure correct value transmission
• Cross-Chain Messaging: Coordinate with host chain for EVVM crediting

Exact Payment Required

The fisher executor must send exactly amount + priorityFee in native currency. Any deviation will cause transaction failure.

Native Coin Representation

Native coins are consistently represented as address(0) throughout the system, from signature creation to EVVM balance crediting.