public function getSignature(array $query = array())
    {
        switch ($this->signature) {
            case self::HMAC_SHA1:
                return $this->getHmacSha1Signature($query);
            case self::RSA_SHA1:
            case self::PLAIN_TEXT:
            default:
                return $this->getHmacPlainTextSignature();
        }
    }