eld-body"><p class="first last">string</p>
</td>
</tr>
</tbody>
</table>
<p>Creates a cryptographic key by fetching random data from
the operating system’s sources (i.e. /dev/urandom).</p>
</dd></dl>

<dl class="method">
<dt id="CI_Encryption::hkdf">
<code class="descname">hkdf</code><span class="sig-paren">(</span><em>$key</em><span class="optional">[</span>, <em>$digest = 'sha512'</em><span class="optional">[</span>, <em>$salt = NULL</em><span class="optional">[</span>, <em>$length = NULL</em><span clas