On Tue, 27 Oct 2009 20:11:35 +0000, Neil Williams wrote:

Or worse to lose your cap because the wrong card picked up.

I suspect this move will be very, very unpopular as people will have to
take cards out of wallets again. Though I really fail to see the point
in payWave, and consider that it has a significant security flaw.


Last time I was in London, I had a new Singapore EzLink in my wallet.
The first Oyster service I used was a bus, and it ready my Oyster fine. I
then found I couldn't use a station gate. So I pull my Oyster out and
present it to the reader on it's own and it's accepted.

Subsequently my wife noticed that every gate I went through started
beeping as I passed.
I then determined that the Singapore card was being detected by the gate
readers from about 15cm or more while still in my pocket. The gates won't
read my Oyster card that far away.

Later experiments with a ticket machine got me the error 'multiple
oysters cards presented' if the Singapore card got any where near the
reader. (With my own Oyster safely out of range btw).

The software in these readers is going to get tricky with multiple
different types of contactless smart card appearing. If the gate supports
paywave, ITSO and Oyster and there is a card that has an Oyster and
Paywave chip in it, when the reader 'excites' the card, two chips are
going to try and send their response at the same time. Now presumably
there is a back-off and retry system, but it's got to extend the read
times, then the gate software is going to get two responses in random
order and it's going to gave to make a decision on which on to use, it
won't necessary be the first response it gets being the most appropriate
to use.

I can see this getting really messy, and not just for nuts like me that
walk around with multiple city's smart cards in my wallet.