[akira2501]

Charged as in has a full and operational battery. A card with a chip in this does not require that. I can also intentionally give someone else my card to effect a purchase and neither myself nor my phone actually has to be there.

Fraud clearly hasn't had a deleterious effect on the entire system, and the penalties for fraud align incentives to fight fraud properly. It's not such a large problem that I'm willing to take steps backwards in terms of functionality and privacy to digitize my purchasing.

[arjvik]

Modern iPhones actually support being used for NFC payments even when they're dead (using a tiny bit of reserve power)

[toomuchtodo]

Wouldn’t it be cool if payment terminals were also Qi enabled so even if the phone was dead it could provide enough power wirelessly to enable payments to be made?

[fastball]

That's actually already how NFC works. The chip being read doesn't need its own source of power – the EM field in the terminal induces a current in the target NFC chip and then uses that same EM field to read the contents. That's why your contactless debit card doesn't need a battery.

Powered devices like a phone have read/write NFC chips that the device will write data to on demand, usually waiting for some form of user auth to make it secure, e.g. an iPhone keeps the NFC chip empty until you specifically request to pay for something, at which point it authenticates you (e.g. with FaceID) and then writes the data to the chip which can then be read by the terminal to authorize payment. Once payment has been made it wipes the NFC chip again.

But a device can have some payment info written to the NFC chip at all times, which is what iPhones do when you have the "Express Transit Card" option enabled – with certain authorized vendors, that payment data stays on your phones NFC chip indefinitely, so you don't need to auth with FaceID and even when the phone is out of battery it can still be read by those authorized terminals.

[toomuchtodo]

Brilliant. TIL!

[unstatusthequo]

If your threat model is a modern phone running out of battery, I suggest an external battery pack. Portable, powerful, and allows you not to carry a slow chip and pin.

[iggldiggl]

Maybe I've picked the wrong phones, but I've also found them to occasionally completely die without any advance warning even if treated carefully, so I remain a bit wary about using them for anything ultra-critical.

And mobile phone providers over here don't guarantee even two nines of reliability, never mind that even 3½ days of no service per year is already too much for some critical things, like being able to get at your money.

And the local public transport association for example tries to disclaim any responsibility for any sort of problems if you're using their mobile ticketing app – if it doesn't work, though luck, your problem, buy a new ticket or pay a fine. Even if you've bought a monthly season ticket there are no special provisions, and the rules don't even differentiate between technical issues caused by myself [1], those caused by third parties (like the mobile service provider) or those caused by the public transport provider respectively its app developers themselves.

[1] Although while I can take care to keep it sufficiently charged, not letting it fall to the ground or whatever, I still can't prevent it from just randomly dying anyway, or the manufacturer issuing some borked update or whatever