You may remember that back in August I got an RFID-shielded wallet; at the time, I was looking for way to test it (preferably free and not involving criminal activity).
I finally got around to testing it using the contactless access control readers at a Sun office, and the results were quite interesting.
I put my Sun badge into the wallet, closed it and waved the card over the reader as normal. The wallet is just a normal billfold-style one, and some people had been predicting that unless it completely wrapped around the card, enough emissions would get in (or out) for the chip to be interrogated. The result? Not a sausage. No reaction, no access.
So I opened the wallet and tried again, this time with the card face down; again, no reaction, either with the card 'wafted' normally, or held against the reader. The only thing between the card and the reader at this point was a transparent plastic 'window'.
Interesting.
I don't know enough about electronics to hold forth on this, but someone I was with suggested that, because the reader has to emit enough power to 'energise' the RFID chip, the same energy could interact with the Faraday mesh so as to produce a 'haze' which itself shields the chip from being read. I dunno, but given the observable results it sounds plausible.
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