Decrypt a license key

How to decrypt a license key (we get it with MySQL query)?

Yes you have a known “defuse.txt” file. But you don’t state a method of how to use it in PHP to decrypt the key. Using a Crypto class would be ok, if it did work.

define('ABSPATH', dirname(__FILE__) . '/');
require_once('SOMEPATH/wp-content/plugins/license-manager-for-woocommerce/includes/Crypto.php');
echo 'ok'; //this works
$cr = new Crypto();
echo 'ok';// this does not work

PS. I was searching through all the similar topics here but found only clues, but no answers.