The Dangers of Verify PIN on Contactless Cards

Contactless / Near Field Communication (NFC) card payments are being introduced around the world, allowing customers to use a card to pay for small purchases by simply placing the card onto the Point of Sale terminal. Although the terminal needs to be able to verify a PIN, it is not clear if such PIN verification features should be available on the NFC card itself. We show that contactless Visa payment cards have (largely redundant) functionality, Verify PIN, which makes them vulnerable to new forms of wireless attack. Based on careful examination of the Europay, MasterCard and Visa (EMV) protocol and experiments with the Visa fast Dynamic Data Authentication transaction protocol, we provide a set of building blocks for possible attacks. These building blocks are data skimming, Verify PIN and transaction relay, which we implement and experiment with. Based on these building blocks, we propose a number of realistic attacks, including a denial-of-service attack and a newly developed realistic PIN guessing attack. The conclusion of our work is that implementing Verify PIN functionality on NFC cards has no demonstrated benefits and opens up new avenues of attack

Another Look at Relay and Distance-based Attacks in Contactless Payments

Relay attacks on contactless e-payments were demonstrated in 2015. Since, countermeasures have been proposed and Mastercard has recently adopted a variant of these in their specifications. These relay-counteractions are based on the payment-terminal checking that the card is close-by. To this end, several other EMV-adaptations have emerged, with the aim to impede dishonest cards cheating on their proximity-proofs. However, we argue that both the former and the latter measures are ineffective. We only sketch possible designs in the right directions, with the idea to pass on the message that these problems should be look at much more carefully. We shortly debate what should and should not be the case w.r.t. confirmation of EMV contactless payments. We also discuss alternative views onto making contactless payments secure against relay-attacks via proximity-checking

Secure Contactless Payment

A contactless payment lets a card holder execute payment without any interaction (e.g., entering PIN or signing) between the terminal and the card holder. Even though the security is the first priority in a payment system, the formal security model of contactless payment does not exist. Therefore, in this paper, we design an adversarial model and define formally the contactless-payment security against malicious cards and malicious terminals including relay attacks. Accordingly, we design a contactless-payment protocol and show its security in our security model. At the end, we analyze EMV-contactless which is a commonly used specification by most of the mobile contactless-payment systems and credit cards in Europe. We find that it is not secure against malicious cards. We also prove its security against malicious terminals in our model. This type of cryptographic proof has not been done before for the EMV specification