# Combine DV Private Key Shares

{% hint style="danger" %}
Reconstituting Distributed Validator private key shares into a standard validator private key is a security risk, and can potentially cause your validator to be slashed.

Only combine private keys as a last resort and do so with extreme caution.
{% endhint %}

Combine distributed validator private key shares into an Ethereum validator private key.

## Pre-requisites

* Ensure you have the `.charon` directories of at least a threshold of the cluster's node operators.
* Ensure you have [docker](https://docs.docker.com/engine/install/) installed.
* Make sure `docker` is running before executing the commands below.

## Step 1. Set up the key combination directory tree

Rename each cluster node operator `.charon` directory in a different way to avoid folder name conflicts.

We suggest naming them clearly and distinctly, to avoid confusion.

At the end of this process, you should have a tree like this:

```shell
$ tree ./cluster

cluster/
├── node0
│   ├── charon-enr-private-key
│   ├── cluster-lock.json
│   ├── deposit-data.json
│   └── validator_keys
│       ├── keystore-0.json
│       ├── keystore-0.txt
│       ├── keystore-1.json
│       └── keystore-1.txt
├── node1
│   ├── charon-enr-private-key
│   ├── cluster-lock.json
│   ├── deposit-data.json
│   └── validator_keys
│       ├── keystore-0.json
│       ├── keystore-0.txt
│       ├── keystore-1.json
│       └── keystore-1.txt
├── node2
│   ├── charon-enr-private-key
│   ├── cluster-lock.json
│   ├── deposit-data.json
│   └── validator_keys
│       ├── keystore-0.json
│       ├── keystore-0.txt
│       ├── keystore-1.json
│       └── keystore-1.txt
...
└── nodeN
    ├── charon-enr-private-key
    ├── cluster-lock.json
    ├── deposit-data.json
    └── validator_keys
        ├── keystore-0.json
        ├── keystore-0.txt
        ├── keystore-1.json
        └── keystore-1.txt
```

{% hint style="warning" %}
Make sure to never mix the various `.charon` directories with one another.

Doing so can potentially cause the combination process to fail.
{% endhint %}

## Step 2. Combine the key shares

Run the following command:

```shell
# Combine a clusters private keys
docker run --rm -v "$(pwd):/opt/charon" obolnetwork/charon:v1.10.0 combine --cluster-dir /opt/charon/cluster --output-dir /opt/charon/combined
```

This command will store the combined keys in the `output-dir`, in this case a folder named `combined`.

```shell
$ tree combined
combined
├── keystore-0.json
├── keystore-0.txt
├── keystore-1.json
└── keystore-1.txt
```

We can verify that the directory names are correct by looking at the lock file:

```shell
$ jq .distributed_validators[].distributed_public_key  cluster/node0/cluster-lock.json
"0x822c5310674f4fc4ec595642d0eab73d01c62b588f467da6f98564f292a975a0ac4c3a10f1b3a00ccc166a28093c2dcd"
"0x8929b4c8af2d2eb222d377cac2aa7be950e71d2b247507d19b5fdec838f0fb045ea8910075f191fd468da4be29690106"
```

{% hint style="info" %}
The generated private keys are in the standard [EIP-2335](https://github.com/ethereum/ercs/blob/master/ERCS/erc-2335.md) format, and can be imported in any Ethereum validator client that supports it.

Ensure your distributed validator cluster is completely shut down before starting a replacement validator or you are likely to be slashed.
{% endhint %}


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