Can a steel woven wallet prevent RFID scanning of credit card information?

  • According to the Popular Mechanics article RFID Credit Cards and Theft: Tech Clinic, the fact that many new credit/debit cards have a RFID chip embedded on it, there is a risk (albeit, small according to the article) that the card would be 'skimmed' - from the article:

    RFID cards do have a unique vulnerability. "Your card can be read surreptitiously. Unless you were paying attention to the guy behind you with a reader, you'd never know you were being skimmed."

    Now, even though the risk is low, there is always a chance. With that in mind, a friend bought me a wallet - a Stainless Steel RFID Blocking Wallet to be precise, that claims to

    prevents 'accidental' reading of your information

    I have this wallet still (it is rather nice looking), so my question is really two-fold:

    • Can a steel woven wallet prevent RFID scanning of credit card information?


    • Is there a practical way I can test this myself?

    (Note: I have no affiliation with anything to do with the manufacture or sale of these wallets)

    an attacker could set up a RFID receiver nearby a reader to skim of cards being actively read (as in being waved in front of the reader), the only way to protect against that is to surround the reader with a faraday cage and have the user put the RFID card inside to be read

    RFID credit cards are designed for short-range operation (1 centimeter), and radio fields drop off with the square of the distance. Even as close as 1 meter you're talking about a field 10.000 times weaker. That also means a reader can protect the card being read by adding a low-power jamming signal at 10 centimeters from the reader. Even at low power, it would overpower the passive RFID card everywhere but in the proximity of the reader itself. And that's without a feedback circuit from the jammer to the reader.

    Just as an interesting aside, this technology looks very similar to the OffPocket. If the construction is sufficiently similar, I would expect it to work in a similar fashion.

    @MSalters In other words, on an elevator is the perfect time to scan someone

    The little secret the RFID industry has been holding onto for decades is that the technology is outdated, unpredictable and unreliable. Just stand close to the wall in an elevator and that will mess up the signal. Hell a fly could land nearby and mess with it.

    I once got a debit card with an RFID chip in it. When I got it, I took it out and made a purchase at a fast food place that read RFID chips; I'm sure you recognize their big golden arches. By the time I got home, someone other than me had already made purchases on it. My current strategy is to refuse RFID cards entirely.

  • tylerl

    tylerl Correct answer

    8 years ago

    Any Faraday cage will do the trick. So a shielding of just about anything conductive, be it aluminum foil, conductive paint, wire mesh, or any of a number of similar alternatives is going to be opaque to radiation. That means no radio waves in or out, which means the RFID signal is blocked.

    Note that the size of the mesh has to be significantly smaller than the wavelength in question; RFID specs are mostly in the MHz range but go as high as 2.4GHz, which is about a 10cm wavelength. So your mesh should be just fine. But aluminum foil is cheaper.

    Thank you for this (+1), 10cm wavelengths can be definitely overcome, the wallet is smaller than that - but you're right, aluminium foil is a heck of a lot cheaper.

    So what you're saying is, giving your credit card a tinfoil hat *might actually be effective?* ;)

    It should be noted that it's not trivial to make a wallet a real Faraday cage. If you have gaps in the cage, it will leak quite easily. If you have ever tried to cover you mobile phone so well it does not get connection to cell tower anymore, you know it's very tricky. See this, for example:

    @Zds a bit of physics knowledge can be helpful. If you understand what you're doing, then it's pretty simple (overlap, contact, etc) but even crappy shielding will be enough to dramatically lower the useful range of the device.

License under CC-BY-SA with attribution

Content dated before 7/24/2021 11:53 AM