RFID tags are those flat radiofrequency modulating thingies The resistor plus the capacitor plus the antenna give each a particular radioemission when placed at an electric field
a technology review person got an award for a newer version yet that person wanted a batteryless RFID that would rotate
identity predictably with time as they found it easy to "lift" the ID from any RFID yet an autochanging RFID would provide greater privacy
I use the word wadded RFID yet the reader can readily imagine two rfid antenna glued together on a tensioned flat that gradually pulls apart over month Its an ordinary effect of certain adhesives Just as effective is an Origami RFID that very gradually changes shape as the memory plastic its printed on changes shape
If the shifting RFID was built as a group like [][][][] the user could even physically move one of them such that the RFIDS privacy was separate from factory programming
really though its just a wadded up RFID where the contact planes have capacitive coupling to create definitively different predictable RF responses with time