Feel free to correct my below logic.
As far as I can tell, HF RFID tags (specifically I've tested MiFare Classic 1kb) have a 48-bit encryption key (default to
0xFFFFFFFFFFFF or something) to protect their contents. A quick Arduino RFID reader I connected together showed me that indeed the blank cards I had purchased could be read, but an old Marriott key could not be. And in the code on the Arduino it did indeed have a customizable key.
From the limited amount of docs I could find on UHF RFID technology, it seems they do not employ this key system and instead everything relies on the serial number so to speak? Is this correct? I can't seem to find much at all in the name of the specifications for these cards at all - they are relatively new and stupid expensive to buy anything related to them. Or, do they in fact use a security protocol to protect unauthorized readers from interfacing with them.
I understand that "UHF RFID" is quite vast, and so if there's a specific protocol or vendor that's more popular and has information available that would be useful. I will be looking at TransCore tags in particular however I have not determined whether they function with other UHF readers or not.