Contactless payment cards, NFC, RFID all use the same basic technology, radio frequencies identification using electro magnetic radio wave frequencies. The RFID microchip is linked to a coiled or circuit board antenna built inside the card, passport or security pass. The cards and passes use an international standard set of radio frequencies; bank and payment cards all use 13.56 Mhz, security passes, keys, product tags typically use 125 kHz. The RFID reader transmits a radio signal which is picked up by your card/pass antenna, this signal powers the microchip in the card or pass, which in turn allows the chip on your card to transmit the data stored back through a radio signal. If the RFID reader transmitting signal is not powerful enough it cannot power the RFID chip on the card or pass, This is where RFID shielding and blocking can reduce the signals to stop data being read from RFID cards.
RFID systems are designed to work at short ranges typically from a few inches but can be read up to a meter with normal RFID readers.
Passive and Active RFID Blocking
RFID blocking cards shields and protectors work in one of several ways They are either passive and active, passive shields or protectors can absorb the RFID signal or deflect it. Active RFID shields or protectors use a microchip and send out either an interfering signal or use or drain the power from the transmitting signal which would power the chip in your card/pass, therefore the chip doesn’t receive enough signal/power to power up and transmit it’s own data signal, protecting your personal data stored on your card.
Deflected or absorbed RFID signals
RFID shielding works in two ways, reflective loss (bounced radio frequency energy) and absorption loss (energy/power dissipated in the shield) both of these elements reduce the transmitting radio frequency signal that would power the RFID chip. The effectiveness of the RFID shielding is a mix of both deflected and absorbed signal.
Deflected or absorbing RFID signals for banking, contactless payment cards signal at 13.56 MHz is far simpler than blocking the security cards and passes at 125 kHz, which needs near field shielding to protect the RFID chip from replying to the reader.
RFID Shielding and Blocking Summary
RFID reader transmits signal, which powers the microchip in the card/pass, the microchip in the cards powers up and sends data out when enough power enters the chip.
Reducing the reader transmitted signal power to under that needed by the microchip in the RFID card means your data is safe. You can do this by increasing the distance from the RFID reader, deflecting/blocking RFID signal, or transmitting data that interferes with the main RFID data signal.