wrote in message
...
On Thu, 14 Oct 2010 11:34:34 +0100
"tim...." wrote:
Interesting, not what I was thinking of (stolen credit cards or
whatever).

I haven't heard of it actually happening 'in the wild' in London

You won't. Not unless the people doing want to bragg and its unlikely
they'll spend then much effort on it just to blow it all in a chatroom.

The reason for my comment was that, at the time, TfL said that they had
the
technology to stop this trick from working.

They're hardly going to say that they can't prevent it.

As the only way that I can see of reliably trapping it is to check the
balance on the card with the balance in the database every time you use it
(not on a bus), I assumed that was what they did.

Unlikely. It would be far too slow to do a central lookup for every single
card each time someone uses it unless the entire database is downloaded to
each gateline every day.

I suppose the alternative is to check the balances "offline" and when you
find a discrepancy, program the gates not to accept that card, but that's
only going to work after the event and there's going to be no way of
stopping someone from using a different cloned card each day.

Or just reusing the same card if they've found a way to reprogram its id
number.

I did meant different "virtual" card. I didn't envisage that they would
have 1000s of physical cards

tim