Blocking contactless payment – or, make your bank card a tinfoil hat

How to protect your bank card and still use your Oyster

Contactless payment cards, touch-for-access ID cards, and prepay travelcards all use the same technology – RFID. This is great in principle, but it means that you can’t keep more than one of them together without either confusing the readers, or accidentally using the wrong one. I wanted to be able to touch my wallet on the London Underground Oyster pads, with my bank card in there too, and have it Just Work.

So, I made some shielding! Metal blocks the radio waves that make RFID work. There are a lot of technical or expensive proprietary solutions out there, some of them intensely cool, some actually practical to carry around with you, but here’s mine.

Take a roll of kitchen foil, and cut a piece 200mm (or 8″) square. Fold it in four, and glue it that way. Leave it to dry, trim it a bit if you need to, and hey presto, that’s your RFID shielding card. I like to glue a piece of heavy paper on either side for strength and interestingness – you could always use it to write medical info on, or use a photo of the five-year-old in your life, or an inspirational poem, or a photographer’s rights card.

Tuck it into your wallet, between your bank card and your travel card, as far away from the travel card as possible – this is because if it’s too close behind the travel card when it’s being read, the reflections can bounce back and confuse a relatively low-power reader.

I’ve been using this design more or less daily for the last few months, so I can guarantee it works. It should also make sure that nobody can read your bank card remotely and clone it, but obviously I haven’t tested this. Knowingly, at least. It does mean I can’t make contactless payments without taking the bank card out of my wallet, which is the way I like it.

I’m going to be selling durable versions, with unique art on each, but please don’t let that stop you making your own! In fact, please do, and please show me your designs.


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