Hiding from Satan’s Radio

I’ve read several articles about the Texas school district being sued for their policy of forcing students to use an ID card embedded with “tracking” technology. The religious freedom angle seems dubious at best (though in Texas you never can tell), but I was surprised by the number of people worried about technology to “track” school children and the supposed dangers of the technology. I’d like to demonstrate how such concerns are overstated with this particular system.

Most of the people discussing this issue seem to have little to no understanding of this technology, so I’m going to try to clear things up a little from the technical perspective and explain how this is a very poor tracking system at best.

The ID cards in question contain an RFID chip, which is an acronym for Radio Frequency ID. There are several different flavors of RFID, and most people have interacted with it in one of several forms for many years now. The most common use over recent decades has been for product theft detection using a simple passive one-bit RFID circuit.

OK, I’ll try to explain what a “passive one-bit RFID circuit” actually is. First let’s cover the “RFID” part.

It’s a simple (yet ingenious) electronic circuit which has a couple of capabilities. At a minimum an RFID chip must have circuitry to store some information in binary format (zeros and ones or possibly just a single “on/off” state), and contain a two-way radio of some kind, including an antenna.

There are active and passive RFID systems. An active RFID uses some sort of power source directly attached to the circuit (such as a battery) to power the circuitry. A passive RFID contains no local power source. Instead it uses the energy in the radio waves coming from the radio transceiver in the reader. That’s the ingenious part in my opinion. As you can imagine, that’s a very tiny amount of power to work with, so passive systems have extremely limited range.  The range of such passive systems can be from a few inches to several yards depending upon the size of the receiving antenna in the reader and the sensitivity of the receiving radio and its ability to discern signal from noise. But it’s mainly all about the size of the receiving antenna.

That’s why there is a large pair of antennae not too far apart near the exit doors of stores which use passive RFID systems for theft control. If the circuit is in an on state, the RFID circuit responds telling the alarm to sound. The circuit can be switched to an off state using the pad on the checkout counter.

By adding to the complexity (and cost) of the circuit, you can store and transmit more than just an on/off state. The more you store and transmit, the more complexity, so most systems just store enough binary information for a short unique ID number.

Most people use an active RFID system when traveling on tollways. The transceiver stuck to your windshield is an active RFID system. Because it uses a battery, it has a much longer range (dozens of yards when combined with large antennae around the toll plazas). That RFID contains a unique ID number which the tollway authority uses to associate with your car and payment information in a database.

Anyone who has been issued a company ID card with and RFID chip used as a key is familiar with the type of chip used in the school district. It’s a passive system (no battery in the card) and the range primarily depends upon the size of the antenna in the reader. If it’s a small antenna (like the one in the block next to the door you need to unlock), you need to get the card very close for the system to work. That’s why you need to do the Backwards Door Jump to get your card to work while it’s still in your back pocket. It stores an ID number which the database associates with your credentials (such as which doors you should be able to unlock).

If you increase the size of the antenna, you can get the system to work at longer ranges (in the several feet to several yard range before the size of the antenna becomes ridiculous).

So, what does this mean to our school children?

First of all, it’s not like a GPS tracker on your phone. The RFID chip has no clue where it is. The only way it can be used for tracking purposes is by setting up a series of readers and sorting through the data collected to find time stamps for when the chip passed near enough to a reader to communicate. In school I could see where you could place readers at every door to actually track students as they passed through them. If a student were, however, kidnapped, there would be no way to find them unless you managed to get within a few yards of them, and they still carried their ID card.

You wouldn’t even be able to ask the tollway system to look for them since they are only designed to work with the active RFID chips. You just couldn’t reasonably get a big enough antenna to be able to activate the passive chip and actually read the ID in a car passing at a high speed.

I haven’t found anywhere just how the system is being deployed at the schools in question, but I did see they implemented it so they could know when a student was in the building, but wasn’t recorded as being in attendance in a particular class for the purposes of getting federal money. (I guess they get money for the student being in the building no matter where the student is.) They don’t even need to track students within the building, so I suspect they didn’t go to the expense of setting up readers at every door to do so. Placing one at each entrance to the building would do the trick.

Secondly, the RFID chips contain no personal information themselves. If someone were to query that chip by using a portable reader, which they would need to do from a very close range (a few feet unless they carried around a huge antenna), they would simply get a number. To parlay that into a home address, for example, they would need to hack into the school database. Of course if someone did that, they would have every student’s home address and ID numbers. I’m not sure why anyone would first want to read the RFID or how that could be used by an Evil Person out to do evil to the student.

I suppose there could be some student hijinks by creating duplicate ID cards (you can order programmable RFID cards and the radios to read/program them for only a few hundred dollars), but I don’t see how a sexual predator, for example, could use RFIDs for tracking or identifying victims.

Do I like the idea of being tracked? No. I have often discussed the pros/cons of systems which can be combined to create tracking information (such as the tollway RFIDs) with my students. But that’s another topic for another time. I see no reasonable way such a system could be used to track students outside of the school.

For homework, I’d like you to think about the number of RFID chips you have. ID card from your employer? Library card? Tollway box in your car? Public transit card? Are you eager to have a Near Field Communication system in your next phone? (That’s just another RFID standard.)

Did you remember to add your car keys to that list? Most automotive keys have an RFID chip in them which your car talks to when you put it in the ignition. If you want to test that, wrap the top part of your key tightly in aluminum foil, sealing it as best you can around the base, then try to start your car.

I wonder if that student in Texas ever plans on owning a modern car…

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