Hello everyone,
I am working on a project which requires RFID.
I have new blank RFID tk4100 cards. I want to give a UID to these blank cards.
Can you please help me with that?
Thank you.

If I remember right blank RFID tk4100 do not exist... it is a 125Khz read only card with a 40 bit (10 HEX digits) UID pre-programmed in each card and this RFID card is read only and not rewritable. —> you can’t change it (there are very few cards where you can change the UID (ie serial number)and they cost 20 or 30 dollars a piece).

This seems an XY problème - what are you really trying to do ?