public static function parseSignature($data)
    {
        if (empty($data)) {
            return null;
        }

        $signatureData = array();

        $list = explode(';', rtrim($data, ';'));
        if (empty($list)) {
            return null;
        }

        foreach ($list as $value) {
            $explode = explode('=', $value);
            if (count($explode) != 2) {
                return null;
            }
            $signatureData[$explode[0]] = $explode[1];
        }

        return $signatureData;
    }