> For the complete documentation index, see [llms.txt](https://dev.guardian.hedera.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.guardian.hedera.com/developer-tools-and-resources/api-reference/profile-apis/creates-a-key.md).

# Creates a Key

**`POST /profiles/keys`**

Creates a new policy signing key for the authenticated user.

**Authentication:** Bearer token required (`Authorization: Bearer <token>`)

**Permission:** `Permissions.PROFILES_USER_UPDATE`

***

## Request

### Request Body

```json
{
  "messageId": "1234567890.123456789",
  "key": "ed25519"
}
```

| Field       | Type   | Required | Description                                  |
| ----------- | ------ | -------- | -------------------------------------------- |
| `messageId` | string | Yes      | Hedera message ID to associate with this key |
| `key`       | string | No       | Key type (e.g. `ed25519`)                    |

***

## Response

### Success Response

**Status:** `200 OK`

```json
{
  "id": "63e3e5e8a01b3c001234abcd",
  "messageId": "1234567890.123456789",
  "key": "ed25519",
  "policyId": "63e3e5e8a01b3c001234abce",
  "policyName": "Example Policy"
}
```

### Error Responses

| Status                      | Description                  |
| --------------------------- | ---------------------------- |
| `401 Unauthorized`          | Missing or invalid token     |
| `403 Forbidden`             | Insufficient permissions     |
| `422 Unprocessable Entity`  | Body or `messageId` is empty |
| `500 Internal Server Error` | Unexpected server failure    |