protected function validateSignature()
    {
        $check = [];
        foreach ($this->data as $key => $value) {
            if ($key !== 'brq_signature') {
                $check[$key] = $value;
            }
        }

        $signature = new Signature($check, $this->secretKey);
        if (empty($this->data['brq_signature']) || (string)$signature !== $this->data['brq_signature']) {
            throw new InvalidSignatureException;
        }
    }