fisherBridgeReceive

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

Receives and validates Fisher bridge transactions from host chain. Verifies EIP-191 signature and increments nonce but doesn't transfer tokens (validation-only function for external chain).

Parameters

Parameter	Type	Description
from	address	Original sender on the host chain (user requesting withdrawal)
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 transfer to the recipient
signature	bytes	Cryptographic signature (EIP-191) from the from address authorizing this transaction.

Access Control

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

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

Workflow

1. Signature Verification

if (!SignatureUtils.verifyMessageSignedForFisherBridge(
    EVVM_ID,
    from,
    addressToReceive,
    nextFisherExecutionNonce[from],
    tokenAddress,
    priorityFee,
    amount,
    signature
)) revert ErrorsLib.InvalidSignature();

Validates EIP-191 signature with EVVM ID integration using structured message format: "{EVVM_ID},fisherBridge,{addressToReceive},{nonce},{tokenAddress},{priorityFee},{amount}".

2. Nonce Increment

nextFisherExecutionNonce[from]++;

Increments Fisher bridge nonce to prevent replay attacks across cross-chain operations.

Validation-Only Function

This function serves as a validation endpoint and does not perform token transfers. Its purpose:

1. Signature Validation: Cryptographically verifies user authorization for Fisher bridge operations
2. Nonce Management: Tracks sequential nonces to prevent replay attacks
3. Access Control: Ensures only authorized Fisher executors can validate transactions
4. Cross-Chain Coordination: Provides secure validation for off-chain Fisher bridge processes

Note: Actual token transfers on the external chain must be handled by separate Fisher bridge mechanisms that coordinate with this validation system.

Signature Message Format

info

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

Fisher Bridge Architecture

Cross-Chain Coordination

1. Host Chain: User authorizes withdrawal via fisherBridgeSend
2. Event Emission: Host chain emits FisherBridgeSend event
3. External Chain: Fisher executor calls fisherBridgeReceive with same signature
4. Validation: External station validates signature and nonce
5. Execution: Off-chain services execute the actual token transfer

Nonce Synchronization

Both host and external chain stations maintain synchronized nonce counters:

• Host Chain: Increments nonce in fisherBridgeSend
• External Chain: Increments nonce in fisherBridgeReceive
• Coordination: Both must use the same nonce value for signature validation

Security Features

Signature Security

• EIP-191 Compliance: Standard Ethereum signed message format
• Replay Protection: Nonce-based prevention of signature reuse
• User Authorization: Cryptographic proof of user consent
• Address Binding: Signature tied to specific sender address

Access Control

• Fisher Authorization: Only authorized executors can validate signatures
• Distributed Validation: Same signature validates on both chains

Nonce Management

• Sequential Increment: Nonces increase monotonically
• Per-User Tracking: Individual nonce counters for each user
• Cross-Chain Sync: Coordination between host and external chains

Integration with External Services

Since this function only validates signatures, external services must:

Monitor Host Chain Events

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

Execute Token Transfers

Based on validated parameters:

• Native Coins: Transfer amount of native currency to addressToReceive
• ERC20 Tokens: Transfer amount of tokenAddress tokens to addressToReceive
• Priority Fees: Handle fee distribution to fisher executor

Error Handling

• Signature Validation: Use this function to verify user authorization (see signature format)
• Nonce Tracking: Ensure nonce synchronization with host chain
• Transfer Validation: Verify successful token transfers

Error Conditions

Error	Condition
InvalidSignature	Signature verification fails
Access Control Revert	Called by unauthorized address (not current fisher executor)

Usage Flow

1. Host Chain: User calls fisherBridgeSend with signature
2. Event Monitoring: External services detect FisherBridgeSend event
3. Signature Validation: Fisher calls fisherBridgeReceive with same parameters
4. Nonce Increment: External station increments user's nonce
5. Token Transfer: External services execute actual transfer
6. Fee Distribution: Priority fees handled by external coordination

Coordination Requirements

For proper fisher bridge operation:

Signature Consistency

• Same signature used on both host and external chains
• Identical parameter values across chains
• Synchronized nonce values

Service Integration

• Off-chain monitoring of host chain events
• External token transfer execution
• Priority fee distribution mechanisms
• Error handling and retry logic

Off-chain Coordination Required

This function only validates signatures and manages nonces. Actual token transfers on the external chain require off-chain services that coordinate between the validation and execution steps.

Nonce Synchronization Critical

Nonce values must remain synchronized between host and external chain stations. Mismatched nonces will cause signature validation failures and break the fisher bridge system.