On Wed, 02 Sep 2015 02:09:20 +0100, the renowned David Billington
wrote:

On 02/09/15 01:22, Joe Gwinn wrote:
In article , Tom Gardner
wrote:

See ads for wallets that prevent skimming credit cards? Are those
considered Faraday cages? I was thinking I could laminate some AL foil
the size of credit cards and have one on top and bottom of the stack of
cards in my wallet to do the job. Sound feasible?
Credit cards require physical contact, be it swiping the magnetic
stripe or communicating with the chip within. Neither is RFID, and so
cannot be skimmed from a distance.

Passports are quite another matter. They very much can be read from
ten or twenty feet. I'm not sure how important it is to prevent this,
but a sheet of 0.003" thick brass shimstock foil folded into the
passport completely prevents this. This costs maybe a dollar.

It is not necessary to enclose the passport. So long as the foil is
close to the antenna coil in the passport, it shorts the local field
out quite well.

If the foil is not removed, not even the legit reader at passport
control works. The officers at passport control do not get excited
about this - just remove the piece of shimstock, and put it back in the
passport later.

Joe Gwinn
Maybe in the US this true but I doubt it, contactless payment technology
has been around in the UK for a few years at least and I would expect in
the US as well, see https://en.wikipedia.org/wiki/Contactless_payment ,
and has been in the news in recent days here as they are raising the
limit for this type of transaction to £30, previously £20 IIRC. I don't
have one and not sure if I want one. A few years ago I was warned by
friends in Holland about IIRC Oyster card travel payment cards being
scanned while in your pocket and details/funds being withdrawn.

I have about six in my wallet that will do contactless payment. Limit
varies by vendor and by some kind of algorithm- sometimes up to $75 or
more, other times a $20 payment will require chip+PIN. More times it
won't work at all with Amex, but will with M/C or Visa even where all
are accepted. It's actually faster than cash where the registers are
set up for it.

It doesn't have a lot of range with the typical readers- maybe 1/2".

The 'Octopus' stored value cards they've been use in Hong Kong for
more than a decade seem to have a bit more range- folks keep them in
their wallet or purse and just flap it against the reader to pay
subway fares etc.. I think some cell phones have it built in.

I think a bit of tin foil would work in the wallet. Maybe even the
aluminized paper in cig packs (do they still have that?).

--sp


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Spehro Pefhany
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