public function testGetObjectKey()
 {
     $permissions = array('print', 'modify', 'copy', 'annot-forms', 'fill-forms', 'extract', 'assemble', 'print-high');
     $enc = new \Com\Tecnick\Pdf\Encrypt\Encrypt(true, md5('file_id'), 2, $permissions, 'alpha', 'beta');
     $result = $enc->getObjectKey(123);
     $this->assertEquals('93879594941619c98047c404192b977d', bin2hex($result));
 }