Card transactions by proxy

Peter Tomlinson pwt at
Mon Apr 4 10:25:54 BST 2011

On 04/04/2011 10:14, Roland Perry wrote:
> In article <32797A21-D2BB-4B1B-A9EA-BC45CA32B17C at>, Ian 
> Batten <igb at> writes
>> I don't feel inclined to book a hotel just to find out, but I'm
>> pretty certain they are an exception.
> Hotels are "different" because they routinely 'reserve' some of the 
> cardholder's credit, although in the relatively recent C&P world they 
> seem to make a nominal ($100 or whatever) charge as a refundable 
> deposit, which doesn't show up on your statement because they cancel 
> the transaction when you checkout.
That triggers something, at a tangent. Transport for London is, as many 
of you will know, adding contactless bank payment to its portfolio of 
technology methods. They want to retain exactly the same daily fare 
capping as they have with classic Oyster cards, so they will daily 
aggregate all the taps that you make with your bank card, and then 
compute overnight the amount to charge to your card account, and ship 
off one transaction to your bank. So your taps are just for card 
authentication and logging of the location of the tap. The question was 
how to do this, and thus was created the concept of the zero value 
transaction between card and terminal (and possibly associated with it 
may be online authentication back to a local server, including checking 
against a hot list - I'm not sure if that online server side transaction 
process will be implemented in London).


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