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It has now been two weeks since we published our paper “Chip and PIN is broken”. Here, we presented the no-PIN attack, which allows criminals to use a stolen Chip and PIN card, without having to know its PIN. The paper has triggered a considerable amount of discussion, on Light Blue Touchpaper, Finextra, and elsewhere.
One of the topics which has come up is the effect of the no-PIN vulnerability on the consideration of evidence in disputed card transactions. Importantly, we showed that a merchant till-receipt which shows “PIN verified” cannot be relied upon, because this message will appear should the attack we presented be executed, even though the wrong PIN was entered.
On this point, the spokesperson for the banking trade body, the UK Cards Association (formerly known as APACS) stated:
“Finally the issuer would not review a suspected fraud involving a PIN and make a decision based on the customer’s paper receipt stating that the transaction was “PIN verified”, as suggested by Cambridge.”
Unfortunately card issuers do precisely this, as shown in a recent dispute over £9,500 worth of point-of-sale transactions, between American Express and a customer. In their letter to the Financial Ombudsman Service, American Express presented the till receipt as the sole evidence that the PIN was correctly entered:
“We also requested at the time of this claim, supporting documents from [the merchant] and were provided a copy of the till receipts confirming these charges were verified with the PIN.”
The issue of evidence in disputed transaction cases is complex, and wider than questions raised by just the no-PIN attack. To help bring some clarity, I wrote an article, “Reliability of Chip & PIN evidence in banking disputes”, for the 2009 issue of the Digital Evidence and Electronic Signature Law Review, a law journal.
Read more at Light Blue Touchpaper...
This content is provided by an external author without editing by Finextra. It expresses the views and opinions of the author.
Patrick Bermingham CEO at Adflex
29 August
Ben Lane VP of Colleague Experience Group at American Express UK
28 August
Alex Kreger Founder & CEO at UXDA
27 August
Luigi Wewege President at Caye International Bank
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