如何判断数字证书的密钥用途为"两者"

      bRet = CertGetIntendedKeyUsage(X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
                                                            pCertContext->pCertInfo, &bUsage, 1);
      if ((bUsage & CERT_DIGITAL_SIGNATURE_KEY_USAGE)

            && (bUsage & CERT_DATA_ENCIPHERMENT_KEY_USAGE))
      {
           strCertType = "BOTH";
      }