# Chain Connector Configuration

The Chain Connector serves as a middleware linking the 2PM Node with blockchain systems. It abstracts the blockchain interface, enabling the 2PM Node to support a variety of different blockchain systems. Additionally, the Chain Connector is responsible for key management and signing tasks required by the blockchain system, ensuring the secure usage of these keys.

### Downloading the Image

Copy and execute the following command to pull the Docker image:

```bash
$ docker pull 2pmmpc/2pm-chain-connector:latest
```

### Initializing Configuration

Before launching the Connector, it is necessary to first initialize its configuration:

Start by creating a new folder named `2pm_chain_connector`, which will serve as the root directory for launching the node:

```bash
$ mkdir 2pm_chain_connector
```

Navigate into the node's root directory and enter the following command:

```bash
$ cd 2pm_chain_connector
$ docker run -it --rm -v ${PWD}:/app 2pmmpc/2pm-chain-connector:latest init
```

After executing this command, a new folder named `config` will be created within the root directory `2pm_chain_connector`. This `config` folder is used to store the node’s configuration files.

### Modifying the Configuration File

Below is an example of a configuration file that needs to be updated according to your specific blockchain and smart contract requirements:

```json
{
  "log": {
    "level": "debug"
  },
  "impl": "chain",
  "host": "0.0.0.0",
  "port": 4500,
  "evm": {
    "nodeAddress": "YOUR_PUBLIC_KEY",
    "privateKey": "YOUR_PRIVATE_KEY",
    "provider": "ws://localhost:8545",
    "gasPrice": "CHAIN_GAS_PRICE",
    "gasLimit": "CHAIN_GAS_LIMIT",
    "chainParam": {
      "chainId": "CHAIN_ID",
      "name": ""
    },
    "identity": {
      "contractAddress": "REPLACE_WITH_REAL_ADDRESS"
    },
    "hfl": {
      "contractAddress": "REPLACE_WITH_REAL_ADDRESS"
    },
    "datahub": {
      "contractAddress": "REPLACE_WITH_REAL_ADDRESS"
    },
    "hlr": {
      "contractAddress": "REPLACE_WITH_REAL_ADDRESS",
      "verifiers": {
        "3": "REPLACE_WITH_REAL_ADDRESS"
      }
    }
  }
}
```

Next, you will need to update the following configurations in the `evm` section of your file:

* **evm.nodeAddress** and **evm.privateKey**: These are used to configure your blockchain wallet address and private key. You can generate these using any EVM-compatible wallet, such as MetaMask. 

{% hint style="info" %}
This wallet account will also be the one you need to use to stake $2PM before joining any subnets, and to receive rewards after performing computing tasks.
{% endhint %}

* **evm.provider**: This should be set to your blockchain node's WebSocket URL.
* **evm.identity**, **evm.hfl**, **evm.datahub**, and **evm.hlr**: These entries correspond to configurations for the IdentityContract, HFLContract, DataHub, and HLR smart contracts respectively. Each `contractAddress` field represents the address of the corresponding smart contract. In the `evm.hlr.verifiers` section, you configure addresses for zero-knowledge proof verifiers specific to different input lengths, for instance, `evm.hlr.verifiers.3` refers to the address for the smart contract PlonkVerifier3.

{% hint style="info" %}
Each subnet has corresponding contracts deployed, and you will need to look up these contracts in the subnet information section (deployed smart contracts) to find them.
{% endhint %}


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