Column: The electromagnetic magic inside a prox

Enter the Radio Frequency Identification (RFID) tag. Embedded in your prox, the RFID contains only an integrated circuit and a coiled antenna. When close to a sensor — which provides power to the card by generating an electromagnetic field — the antenna transmits data stored in the circuit. Once the data in your card is recognized by the sensor, the magic happens: A lock turns, and you’re in.

While everyone knows that proxes unlock doors, few realize that their use is also tracked in a database that Public Safety monitors during emergencies, the Honor Committee consults during investigations and administrators can access for (hopefully benign) purposes.

Outside Princeton’s gates, RFID technology is widely used for commercial record keeping. Retailers like amazon.com slip RFID tags into books to streamline shipping. Knowing what’s inside is as simple as scanning the boxes holding the books. And it’s not just merchandise: In a 21st century version of branding, farmers often tag cows with sub-dermal RFID tags for quick identification.

The idea of tiny, hidden RFID tags pervading our daily lives — ready to tag, scan and identify — causes instinctual discomfort, especially considering the privacy ramifications of widespread RFID use. RFID technology is remarkably insecure. A tech-savvy stalker armed with a sensor could access your personal information simply by walking close by and could gain access to buildings by retransmitting the information to any RFID scanner on campus.

RFID tags are used in a host of potentially startling applications, including in highway tollbooth systems like E-Z Pass. If you go through an E-Z Pass at 5 p.m., and drive through another one 100 miles later at 6 p.m., police can easily calculate that you were speeding at some point during your journey. They simply look at the time you passed each booth and calculate the distance between them. The RFID tags provide them with enough information to glean those facts and write you a ticket.

In the not-so-distant future, it’s conceivable that RFID tags will be used in even the most routine activities, like buying clothes. Imagine, for example, walking into a future Nike store in New York City to purchase a pair of shoes with your credit card. Future Nike has put RFID tags in the soles of every pair of sneakers. When you step into another Nike store a few weeks later in Los Angeles, the RFID reader under the rug alerts the clerk to your name and purchase history. The tag in your shoes, linked to some pertinent information about you from your credit card, now makes you far from anonymous.

In some stores, a version of this future is already here. Galeria Kaufhof, a department store based in Cologne, Germany, equipped its dressing rooms with RFID readers. When customers try on the RFID-tagged clothes, a screen informs them of available sizes and colors.

The ubiquity of RFID tags, and the fact that they are paper-thin, easily hidden and don’t require physical contact to work, raise a host of privacy issues to consider.

Pure anonymity is, in many ways, a fiction of our collective imaginations. If you use e-mail, Google or Facebook, or simply browse the web, chances are you’re being tracked, and your preferences, interests and browsing history are now sitting in databases all over the world, waiting to be analyzed. RFID tracking is just the tip of the iceberg when it comes to technology and it’s impact on personal privacy.