public function verify(Crypto $crypto = null): bool
    {
        $crypto = $crypto ?: Crypto::getDefault();
        $data = $this->_certificationRequestInfo->toASN1()->toDER();
        $pk_info = $this->_certificationRequestInfo->subjectPKInfo();
        return $crypto->verify($data, $this->_signature, $pk_info,
            $this->_signatureAlgorithm);
    }