# Use a signer

As ledger devices are able to install applications that will allow to be compatible with different blockchains,
we have created these kits.

Each **signer kit** is coming along with a Ledger Embedded App (ex: _signer-kit-eth_ is coming with _ledger app ethereum_ ).

The main goal of each signer is to ease interaction with the app in the most seamless way possible.

> **Note:** We will show the usage of the signer with the Ethereum signer.
> The same logic can be applied to the other signers.

## Installation

> **Note:** This module is not standalone; it depends on the [@ledgerhq/device-management-kit](https://github.com/LedgerHQ/device-sdk-ts/tree/develop/packages/device-management-kit) package, so you need to install it first.

To install the `device-signer-kit-ethereum` package, run the following command:

```sh
npm install @ledgerhq/device-signer-kit-ethereum
```

## Usage

To initialize an Ethereum signer instance, you need a Ledger Device Management Kit instance and the ID of the session of the connected device. Use the `SignerEthBuilder` along with the [Context Module](https://github.com/LedgerHQ/device-sdk-ts/tree/develop/packages/signer/context-module) by default developed by Ledger:

```typescript
// Initialize an Ethereum signer instance using default context module
const signerEth = new SignerEthBuilder({
  dmk,
  sessionId,
  originToken: "origin-token",
}).build();
```

> **Note:** The `originToken` parameter is required by the default context module to work.
> Token should be delivered by Ledger, otherwise the Transactions Checks will not be available.

You can also configure the context module yourself:

```typescript
// Initialize an Ethereum signer instance using customized context module
const signerEth = new SignerEthBuilder({ dmk, sessionId })
  .withContextModule(customContextModule)
  .build();
```