On 17/12/2012 07:55, Neil Williams wrote:

Roland Perry wrote:

Which implies that an almost unlimited amount of historic transaction
information is sent with every wave.

Not really, the retailer's POS system can do this with nothing more than
the card number.

Bus ticket inspections could be done by having the ticket machine print out
a ticket containing the last 4 digits of each credit card used during that
journey, perhaps. Or more technologically, communicate it to the
electronic gripping irons.

My understanding is that a (very) small amount of data can be written to
an EMV-standard contactless card - i.e. the card itself can prove that
it has been validated (e.g. where and when).