I'm working on a project. The basic Idea is I want to use NFC phone's UID as an unique identifier for log in process. User will be provided a client, where they only need to tap Log in and it will read the NFC UID from the phone, send it to the server, if it's registered then the log in process is successful. But I'm totally new to the technology so I want to ask if doing so is really possible? I've been researching for awhile and found some articles say that the UID is randomly generated each time it's scanned. Is that true? Is there any real fixed UID that can be used to serve my purpose? Please help me, thanks!