The fine art of hacking RFID tags for the Internet of Things

An RFID tag is modified by cutting out a small part its antenna (silver ribbon) and placing a small light-sensing phototransistor or temperature-responsive resistor (thermistor) on it. Credit: University of Waterloo
An RFID tag is modified by cutting out a small part its antenna (silver ribbon) and placing a small light-sensing phototransistor or temperature-responsive resistor (thermistor) on it. Credit: University of Waterloo

A team of researchers at the University of Waterloo (Canada) have come up with an inexpensive and novel way to create smart devices that don’t require charging or batteries. What they did is to take standard RFID (radio frequency identification) tags and hacked them to be sensors that can sense temperature and light levels.

RFID tags usually provide two things to a device that reads it: identification and location. The team took a stock RFID tag, removed the plastic cover, cut out a small portion of the tag’s antenna with scissors, and then attached a sensor across the gap created to complete the circuit.

The team gave an RFID tag the ability to “see” by putting a phototransistor on the spot they carved out with scissors. When the phototransistor was exposed to light, it “tuned” the RFID tag’s antenna differently and caused a change in the signal detected by the reader. On the reader, the team was able to develop an algorithm to monitor the changes in the signal — therefore knowing how it senses light or dark.

Other hacks included adding a thermistor (a temperature-responsive resistor) to the circuit to make the RFID tag sensitive to temperature changes, as well as adding a simple switch to a tag to make it a touch-sensitive keypad. As one of the researchers, Professor Omid Abari, noted, “Our main contribution is showing how simple it is to hack an RFID tag to create an IoT (internet of things) device. It’s so easy a novice could do it.”

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