Methods and apparatus for preserving privacy in an RFID system
A card comprises an antenna configured to generate and receive radio frequency signals, a chip coupled with the antenna, the chip configured to store sensitive information and communicate the information to an authorized reader via the antenna, and a switching mechanism configured to tune and detune the antenna relative to the chip to enable and disable respectively, the chips ability to communicate the sensitive information via the antenna.
1. A method for protecting the privacy of information stored on an RFID tag comprising an antenna, a switching mechanism, and a chip, the chip including an impedance matching circuit, the method comprising:
activating the switching mechanism to electrically couple a first leg of the antenna to a second leg of the antenna;
in response to activating the switching mechanism, matching the impedance between the chip and antenna so as to tune the antenna relative to the chip via the impedance matching circuit, wherein said impedance matching circuit is configured to account for the effects of a substrate to which the RFID tag is attached;
communicating the information to a reader when the antenna is tuned;
deactivating the switching mechanism to electrically decoupled the first leg of the antenna from the second leg of the antenna; and
in response to deactivating the switching mechanism, mismatching the impedance between the chip and antenna so as to detune the antenna relative to chip after the information is communicated to the reader.
2. The method of claim 1 , wherein activating the switching mechanism comprises pushing a button.
3. The method of claim 1 , further comprising placing the RFID tag within proximity of the reader before communicating the information to the reader.
4. A method for tuning an antenna relative to a chip in an RFID tag, the antenna comprising a the main portion and a leg portion that is not electrically coupled with the main portion, the chip comprising an impedance matching circuit, the method comprising:
configuring a switching mechanism such the main portion and the leg portion of the antenna are electrically coupled when the switching mechanism is activated and electrically decoupled when the switching mechanism is deactivated;
activating the switching mechanism so as to couple the main portion and the leg portion of the antenna;
configuring the impedance matching circuit so as to tune the antenna relative to the chip when the switching mechanism is activated such that there is a good impedance match between the chip and the antenna when the switching mechanism is activated; and
configuring the impedance matching circuit so as to detune the antenna relative to the chip when the switching mechanism is deactivated such that there is an impedance mismatch between the chip and the antenna when the switching mechanism is deactivated,
wherein the impedance matching circuit is further configured to account for the effects of a substrate to which the RFID tag is attached.
5. The method of claim 4 , further comprising accounting for external elements when configuring the impedance matching circuit.