如何获取Java中每个用户/ PC的唯一ID或字符串？

As you can read in the title, I'm looking for a unique ID or String to identify users or PC's. I'm creating a Java script with a security method which uses a unique ID or String. I used the MAC Address before, but since an update at the developers I'm coding for, this isn't allowed anymore. Is there another way to get some sort of unique ID to identify users or pc's which is allowed? For more information: I'm coding for RSBot, which is an open-source program which runs user created Java scripts.As you can read in the title, I'm looking for a