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A Technical RFID Primer

Posted by Hemos on from the learn-more-about-it dept.

gManZboy writes "Roy Want, principal engineer at Intel Research, has a pretty meaty technical overview of RFID up at Queue. If you ever wondered how these little things actually work it's worth a read. For instance, I was intrigued to find out how the tags (which are generally battery-free) can absorb enough energy from RFID readers to then power up and transmit their own signal back to the reader."

3 of 131 comments (clear)

  1. RFID isn't a problem-free technology for retailers by hrbrmstr · · Score: 5, Informative
    A little over a week ago, Yahoo! posted a story from TechWeb about IBM's experiences with Wal-Mart in their RFID deployment.
    During the deployment, IBM consultants have encountered interference from handheld devices such as walkie-talkies, forklifts, and other devices typically found in distribution facilities. And nearby cell-phone towers, which transmit at the high end of the frequency band, sometimes leak unwanted radio waves into the RFID readers. Bug zappers in the grocery sections of the pilot stores also caused interference. "When you have a bug that hits the zapper, the RF power generated by the interaction with the bug produces noise in the coax cables," says Douglas Martin, executive consultant at IBM Global Services.
    Regardless of how much a retailer's internal facility might disrupt their ability to monitor me, I still plan on getting one of RSA's RFID jammers when they're out.
    --
    Mind the gap...
  2. transmission vs. reflection and foil bags by Wansu · · Score: 4, Informative


    I was intrigued to find out how the tags (which are generally battery-free) can absorb enough energy from RFID readers to then power up and transmit their own signal back to the reader."

    The high frequency tags don't actually transmit. They change the impedance of their antenna to modulate the reflection back to the transmitter.

    Another problem the article didn't mention is that bags lined with aluminum or copper foil will thwart these systems.

    --
    Wansu, th' chinese sailor
  3. Lukas Grunwald's Blackhat pres. + Linux tools! by phreakmonkey · · Score: 5, Informative
    Lukas Grunwald did an excellent presentation at BlackHat USA 2004 about this very subject.

    The most interesting thing that I learned was that most all RFID tags have a 128 byte "user data" buffer than can be read or written by ANY RFID gate. (Ie: you can put an RFID interface on your laptop and query the tags and change the "user data" portion on them.)

    Obviously, this means that any application that is sensitive to tampering should only use the hard-coded serial numbers, not the "user data" area... but history has told us how well people stick to "common sense" security practices in their implementations.

    His paper and the Linux tool that allows you to query and change the data are located here: http://www.blackhat.com/html/bh-media-archives/bh- archives-2004.html (scroll down to Lukas Grunwald under "Layer 0".