None — FROM VISA:
"First, to give you some background on Visa's contactless payment platform. Visa payWave is Visa's contactless payment technology. It facilitates fast and convenient transactions at the point of sale and eliminates the requirement for a consumer to make physical contact with the terminal when making a purchase (therefore "contactless"). Consumers simply hold the card or phone in front of the contactless terminal in order to pay.
To your point about security, ensuring payment security is one of Visa's highest priorities and Visa payWave enabled payment cards are no exception. Visa payWave cards are as secure as traditional cards and meet all the same standards for security and more.
Specifically to answer the question you had below, there have been no reports of fraud perpetrated by reading Visa payWave cards. In keeping with evolving best practices in the industry, Visa mandates that Visa payWave cards do not transmit the cardholder's name during a transaction. So, intercepting a Visa payWave transaction (aka electronic pickpocketing) results in less sensitive information than when handing a card over to a clerk. Neither the cardholder name nor the three-digit security code on the back of the card are available when the card is read via a contactless reader."
WPXI
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