[kybernetikos]

This attack (and some variants of it, e.g. fooling the proximity detection or man in the middle) work because the acknowledgement action that the user does is simply having the device nearby. This seems like a poor choice of acknowledgement action for something that transfers money. Payment devices should probably have a physical or soft button that you have to press to acknowledge payment.

[underdeserver]

Strong disagree. The usability hit is not worth the added security. Having a cutoff for PIN entry requirement and the card issuer taking responsibility for fraud means customers are quite safe (as long as they look at their charges).

[kybernetikos]

Work could be done to make it more usable. With a phone, it could be a button you could press just by holding it. With a smart watch, it could be hooked into any kind of bluetooth sensor. The point is that in normal society, you don't have that much control over who and what gets into proximity with you, and having a system where anything that does get into proximity can take money from you without you even acknowledging that in any way is just a bad way of doing things.

[samhw]

You could do something like "you need to be physically holding the card with your hand", which would complete some circuit. I can't think of many cases where that wouldn't work, except perhaps people who don't take their cards out of their wallets(?).