> For the complete documentation index, see [llms.txt](https://docs.finema.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.finema.co/api-tutorials/did-api/add-key.md).

# Key Series Addition

Once a DID is registered, its owner has the option to add more key series with `did_add` operation. This operation requires another active key series to sign and verify its HTTP request. In the `did_add` request, the client must specify the SHA-256 hash of the first public key in the new series must be given.

{% hint style="warning" %}
A new key series cannot be used to sign and verify its own addition. 
{% endhint %}

## did\_add

<mark style="color:green;">`POST`</mark> `https://test-network.finema.co/did/<did_address>/key`

#### Request Body

| Name            | Type   | Description                                                                         |
| --------------- | ------ | ----------------------------------------------------------------------------------- |
| operation       | string | The method's name that is "did\_add".                                               |
| did\_address    | string | The DID address.                                                                    |
| current\_key    | string | The current public key in the series. It is used to verify the request's signature. |
| next\_key\_hash | string | The SHA-256 hash of the next public key in the series.                              |
| new\_key\_hash  | string | The SHA256 hash of the first public key in the new series.                          |
| nonce           | number | The request nonce.                                                                  |

{% tabs %}
{% tab title="200 The operation name, DID address (\<did\_address>) and a unique ID for the added key series will be given as the response." %}

```
{
     "operation": "did_add",
     "did_address": "did:idin:afb7ba88c76edbda55c344b70ae0cf0556d770ec256820d7185000de395391b5",
     "key_id": "f975e5f2e4a06fced2d65bd59e12c33c901814555b026264b8377ace79cee60a"
}
```

{% endtab %}

{% tab title="422 " %}

```
{
    "errors": [
        {
           "status": 422,
            "title": "Invalid Attribute",
            "detail": "the server cannot process the request",
        }
    ]
}
```

{% endtab %}
{% endtabs %}

## Example Message and Request

```
{
    "operation": "did_add",
    "did_address": "did:idin:afb7ba88c76edbda55c344b70ae0cf0556d770ec256820d7185000de395391b5",
    "current_key": "-----BEGIN PUBLIC KEY-----\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEu7ZonDYYEnCTvPA9H8eM9JxaQGHB\nMzLgxUMo58SXoJKIzt93kQK/bhwdPnFaEfQhiLB5VkOFgn2qKgScdIcXVw==\n-----END PUBLIC KEY-----",
    "next_key_hash": "ccca6c11cfa40f266968f6a71bba495bc73e97d882eb74523784769d43175cd5",
    "new_key_hash": "2a37b9edff78e6c0d5ef90888b29fa649498094a4970a660adcd5e0b3161e66f",
    "nonce": 1
}

```

The above message can then be encoded in Base64 and signed with ECDSA to obtain the following HTTP request

```
{
    "message": "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",
    "signature": "MEUCIQCfZqZodAu7pTgb9xLHdi+DWTrwbCjI4z18RXAQFcXp0AIgf3VyAP86Yr6gMqUiMg97YJRx67ELwlaKFhh9Bolj3cY="
}
```