public function getHash() {
		$mediaSalt = Configure::read('Imagine.salt');
		if (empty($mediaSalt)) {
			throw new InvalidArgumentException('Please configure Imagine.salt using Configure::write(\'Imagine.salt\', \'YOUR-SALT-VALUE\')');
		}

		if (!empty($this->request->query)) {
			$params = $this->request->query;
			unset($params[$this->_config['hashField']]);
			ksort($params);
			return Security::hash(serialize($params) . $mediaSalt);
		}
		return false;
	}