---
title: Cross Chain Messaging
icon: Send
---

## Introduction

<br/>
<picture style={{height: '300px'}}>
    <source srcSet="/diagrams/portal-1-light.png" media="(prefers-color-scheme: light)" />
    <source srcSet="/diagrams/portal-1-dark.png" media="(prefers-color-scheme: dark)" />
    <img src="/diagrams/portal-1-dark.png" alt="Image" className="image" />
</picture>

Manage Groups and Prove from any Chain.

## Interface

Call the following functions on the forwarder contract to pass messages to the base chain GroupManager Contract.

```solidity filename="IForwarder.sol"
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IForwarder {

    // Directly verify proofs on the base chain.
    function verifyProof(
        uint256 groupId,
        uint256 merkleTreeRoot,
        uint256 signal,
        uint256 nullifierHash,
        uint256 externalNullifier,
        uint256[8] calldata proof
    ) external;

    // Directly send `abi.encodeWithSelector` messages to the GroupManager Contract.
    function _sendInternal(
        bytes memory __selectorEncodedPayload
    ) external;
}
```

## Integration

<Steps>

<Step>
### Grab the required Addresses
- [Deployment addresses](/integration/deployments)
</Step>

<Step>
### Setup Contracts

```solidity filename="OmnidDemo.sol"
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import './IForwarder.sol';

contract OmnidDemo {

    IForwarder forwarder;
    constructor (address _forwarderAddress) {
        forwarder = IForwarder(_forwarderAddress);
    }

    function verifyProof(
        uint256 groupId,
        uint256 merkleTreeRoot,
        uint256 signal,
        uint256 nullifierHash,
        uint256 externalNullifier,
        uint256[8] calldata proof
    ) public {
        forwarder.verifyProof(
            groupId,
            merkleTreeRoot,
            signal,
            nullifierHash,
            externalNullifier,
            proof
        );
    }

}
```
</Step>

<Step>
### Deploy 🎉
</Step>
</Steps>