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Comment by noobermin | Hacker News Reader

I will say this is a cool project. However, the implementation of the idea in reality is even worse than NFC. While NFC is useful in many contexts, it then requires you to put a faraday cage around your card and manually turn on or off the NFC to not get your money stolen, and even then can be circumvented. Even further relaxing the distance constraints even makes it even easier to steal money. I'd imagine a lot of the engineering would go into making it safe (having some set up such that the US sounds vary to some degree...then may be even an authentication protocol..then...then...then...

The moment I saw the headline, I was incredulous. The actual project implementation in the article is a rather cool hack, so props to the author. I dread the day someone actually picks this up, assuming someone does actually choose to.

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Cool technology, bad problem. I fully agree getting more distance is problematic. Not even in the sense of getting your data stolen, but also to allow pro active payment. I mean you want the customer to do an action (holding the card close to a device which shows the amount deducted) to conclusively agree to that payment. Not the cashier presses a button, and anybody too close pays for it.

modem/phone couplers, anyone?

Phone carriers cut off the frequency spectrum.

i'm just referring to the acoustic isolation from the mechanical coupler. obviously (?) the passband for telephone comms is far short of ultrasonic

What do you mean by acoustic isolation?

https://en.wikipedia.org/wiki/Acoustic_coupler

Yes, but what can ultrasonic do here?

The complaint was that the wrong payment can be made, because audio leaks.

yes. Now I understand, but then the stated advantage of longer distance is also gone...

How would you “steal” money from a contactless card or a phone?

For example: NFC Proxy?

1) Gain access to something like a Stripe Terminal (https://stripe.com/gb/terminal) You should probably avoid using your real identity here.

2) Type in a charge like $50

3) Discretely wave the device at your targets wallet

4) Repeat steps 2-3 as much as possible in a short amount of time.

5) Hope you can withdraw the funds before anyone notices.

I don't think this is a wildly plausible attack and also at least here in the UK your targets card issuer takes 100% liability for fraudulent charges.

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.

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).

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(?).

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.

> 1) Gain access to something like a Stripe Terminal (https://stripe.com/gb/terminal)

Getting a payments terminal is not easy, this would requires ID verification and working business bank account (acquirer), this terminals are highly regulated. Someone doing this can get caught easily by just a couple of customers reporting the fraudulent transactions. This is very small risk and is rarely seen.

Most new wallets ac as faraday cages.

> 3) Discretely wave the device at your targets wallet

Phone payments generally require the phone to be unlocked.

Also, it's a credit card transaction: the user will complain later, attacker will get into legal trouble, and user will be refunded fully.

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