## `deriveKey`

### Signature

```solidity
function deriveKey(string calldata mnemonic, uint32 index) external returns (uint256 privateKey);
function deriveKey(string calldata mnemonic, string calldata derivationPath, uint32 index) external returns (uint256 privateKey);
```

### Description

Derives a private key from a given mnemonic phrase or mnemonic file path.

The first signature derives at the derivation path `m/44'/60'/0'/0/{index}`.
The second signature allows you to specify a custom derivation path.

### Parameters

| Parameter        | Type     | Description                              |
|------------------|----------|------------------------------------------|
| `mnemonic`       | `string` | The mnemonic phrase or path to mnemonic file |
| `derivationPath` | `string` | Custom HD derivation path (optional)     |
| `index`          | `uint32` | The index in the derivation path         |

### Returns

| Type      | Description               |
|-----------|---------------------------|
| `uint256` | The derived private key   |

### Examples

Derive the private key at path `m/44'/60'/0'/0/0`:

```solidity [test/DeriveKey.t.sol]
string memory mnemonic = "test test test test test test test test test test test junk";
uint256 privateKey = vm.deriveKey(mnemonic, 0);
```

Derive the private key at a custom path `m/44'/60'/0'/1/0`:

```solidity [test/DeriveKey.t.sol]
string memory mnemonic = "test test test test test test test test test test test junk";
uint256 privateKey = vm.deriveKey(mnemonic, "m/44'/60'/0'/1/", 0);
```

### Related Cheatcodes

* [`rememberKey`](/reference/cheatcodes/remember-key) - Stores a private key in forge's local wallet
* [`addr`](/reference/cheatcodes/addr) - Computes address from private key

### See Also

* [`deriveRememberKey`](/reference/forge-std/derive-remember-key)