code: private byte[] computeHmacSha(byte[] keyBytes, byte[] text) {
          try {
              Mac hmac = Mac.getInstance("HmacSHA512");
              SecretKeySpec macKey = new SecretKeySpec(keyBytes, "RAW");
              hmac.init(macKey);
              return hmac.doFinal(text);
          } catch (GeneralSecurityException gse) {
              throw new UndeclaredThrowableException(gse);
          }
      }
docs: Returns the HMAC-SHA hash with {@code keyBytes} as the key, and
  {@code text} as the message.
  
  @param keyBytes
  the bytes to use for the HMAC key
  @param text
  the message or text to be authenticated
  
  @return the HMAC-SHA hash with {@code keyBytes} as the key, and
  {@code text} as the message.