**Usage**: `new HDPrivateKey(data)`  
**Description**: Instantiate an instance of a hierarchically derived private key (read more about HD in the [BIP-32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki)).

| parameters | type                 | required | Description                      |
| ---------- | -------------------- | -------- | -------------------------------- |
| **data**   | Object/Buffer/String | yes      | A Buffer, JSON string, or Object |

**Returns**: {HDPrivateKey} A new instance of a HDPrivateKey

## HDPrivateKey.isValidPath(path)

**Description**: Verifies that a given path is valid.

**Parameters**:

| parameter | type          | required | Description |
| --------- | ------------- | -------- | ----------- |
| **path**  | String/Number | yes      | A path      |

**Returns**: {Boolean}

## HDPrivateKey.isValidSerialized(data, network)

**Description**: Verifies that a given serialized private key in base58 with checksum format is valid.

**Parameters**:

| parameter   | type           | required | Description                                                                            |
| ----------- | -------------- | -------- | -------------------------------------------------------------------------------------- |
| **data**    | String/Buffer  | yes      | the serialized private key                                                             |
| **network** | String/Network | no       | optional, if present, checks that the network provided matches the network serialized. |

**Returns**: {Boolean}

## HDPrivateKey.getSerializedError(data, network)

**Description**: Checks what's the error that causes the validation of a serialized private key in base58 with checksum to fail.

| parameter   | type           | required | Description                                                                            |
| ----------- | -------------- | -------- | -------------------------------------------------------------------------------------- |
| **data**    | String/Buffer  | yes      | the serialized private key                                                             |
| **network** | String/Network | no       | optional, if present, checks that the network provided matches the network serialized. |

## HDPrivateKey.fromSeed(hex, network)

**Description**: Verifies that a given serialized private key in base58 with checksum format is valid.

**Parameters**:

| parameter   | type           | required | Description                        |
| ----------- | -------------- | -------- | ---------------------------------- |
| **hex**     | String/Buffer  | yes      | seed serialized as string a buffer |
| **network** | String/Network | no       |                                    |

**Returns**: {HDPrivateKey}

## HDPrivateKey.fromString(str)

**Description**: Instantiate a HDPrivateKey from a string representation

**Parameters**:

| parameter | type   | required | Description |
| --------- | ------ | -------- | ----------- |
| **str**   | String | yes      |             |

Returns : {HDPrivateKey} An instance of HDPrivateKey

## HDPrivateKey.fromObject(obj)

**Description**: Instantiate a HDPrivateKey from an object

**Parameters**:

| parameter | type   | required | Description |
| --------- | ------ | -------- | ----------- |
| **obj**   | Object | yes      |             |

Returns : {HDPrivateKey} An instance of HDPrivateKey

## HDPrivateKey.fromBuffer(buf)

**Description**: Instantiate a HDPrivateKey from a buffer

**Parameters**:

| parameter | type   | required | Description |
| --------- | ------ | -------- | ----------- |
| **buf**   | Buffer | yes      |             |

Returns : {HDPrivateKey} An instance of HDPrivateKey

## .deriveChild(arg)

**Description**: Get a derived child based on a string or number.  
If the first argument is a string, it's parsed as the full path of derivation. Valid values for this argument include "m" (which returns the same private key), "m/0/1/40/2'/1000", where the ' quote means a hardened derivation.  
If the first argument is a number, the child with that index will be derived. If the second argument is truthy, the hardened version will bederived. See the example usage for clarification.

**Parameters**: None.

**Returns**: {string} A hex encoded string of the HD private key

```js
const parent = new HDPrivateKey('xprv...');
const child_0_1_2h = parent.deriveChild(0).deriveChild(1).deriveChild(2, true);
const copy_of_child_0_1_2h = parent.deriveChild("m/0/1/2'");
assert(child_0_1_2h.xprivkey === copy_of_child_0_1_2h);
```

## .toString()

**Description**:Will return a string representation of the HD private key

**Parameters**: None.

**Returns**: {string} A hex encoded string of the HD private key

## .toJSON() / .toObject()

**Description**: Will return an object representation of the HD private key

**Parameters**: None.

**Returns**: {Object} A plain object with the HDPrivateKey properties

## .toBuffer()

**Description**: Will return a buffer representation of the HD private key

**Parameters**: None.

**Returns**: {Buffer} A buffer of the HD private key

## .inspect()

**Description**: Will return a string formatted for the console

**Parameters**: None.

**Returns**: {string} Console representation of this extended private key.

```js
const hdPrivateKey = new HDPrivateKey(...);
hdPrivateKey.toInspect() // <HDPrivateKey: xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi>
```