I'll discuss a bit of passive RFID at FOSDEM ... I think there are two parts to the question: detecting RFID measurement attempts on the one hand, and decoding the backscattered signal on the other hand. Detecting RFID is, imho, obvious: because the backscattered signal decays as 1/d^6 for an inductive coupling, and because of the inefficiency of the rectifier diode when considering silicon based RFID, the emitted power must be very strong, and making a simple carrier detection of a 10-W emitter is very simple (since the emitted carrier power decays as 1/d^2). Getting the backscattered (amplitude modulated) signal is a different story, with an efficient signal to noise ratio requiring the removal of the carrier, which I cannot think of an obvious strategy if the emitted carrier is not recorded as well for a coherent demodulation.
JM > On 27/12/15 19:03, Marcus Müller wrote: > > The problem is that technically, the energy sent out by an RFID > > reader isn't big enough to detect readers from afar; they are > > near-field devices, as opposed to the typical far-field antenna > > based radio transmitters. > > > > If the sniffer was carried in close proximity to the card itself (e.g. > the card and sniffer in a backpack) and the backpack passed a hidden > RFID scanner at the entrance to a shop, would the sniffer be able to > detect the communication? _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
