In message , at 10:57:09 on
Fri, 14 Dec 2012, Paul Corfield remarked:
Do contactless credit cards store the journey like Oyster cards?
Blub from TfL says that if an inspector gets on to check tickets, you
just show your card in the same way as Oyster.

My guess would be that the contactless chip is written to with basic
txn info when successfully presented to the bus reader.

VISA say "Only minimal account and information is stored on a Visa
payWave card, which is no more than traditional magnetic stripe cards or
contact chip cards".

On the other hand, a Smartcard newsletter says: "Retailers will be able
to use data stored inside Visa payWave payment card to deliver targeted
messages at the point of sale. For example, a coffee chain can recognize
an infrequent customer that has not been to the chain in over 30 days,
and instantly print an offer at the bottom of the card receipt,
encouraging the customer to return soon."

Which implies that an almost unlimited amount of historic transaction
information is sent with every wave. Which doesn't seem very practical
(and how/when is the data for the latest transaction added to the card,
that implies a 2-way data flow).

I can't see any indication in a 200+ page technical spec I have for
payWave that anything is written back to the card, and the flow chart
for processing an EMV card suggests that the card can be removed from
the RF field before the terminal has done any of its authentication
activity - so at that stage it's unknown whether the transaction
succeeded or not.

There is, however, a "Transaction counter" on the card, although
updating it is optional.

I've asked about this on another specialist list and will report back if
we can nail this down at all.
--
Roland Perry