4 ms·

Contactless is not less secure than magstripe. I don't know where you got that from. You can't make a fake contactless card, because each card has a private ke

by yarcob 5y ago

Contactless is not less secure than magstripe. I don't know where you got that from. You can't make a fake contactless card, because each card has a private key that you can't extract. But it's trivial to make a fake magnetic stripe card. One type of fraud with EU credit cards works like this: Criminal collects credit card numbers and pins by adding a hidden magnetic stripe reader to an ATM and a video camera, then create a fake magnetic card, and then withdraw money with fake card + PIN somewhere abroad where magnetic stripes are still allowed. For this reason, my bank disables withdrawals from abroad by default, and you need to manually enable world wide payments in the online banking app.

ohazi 5y ago
You're correct that you can't easily clone an NFC card from RF interactions alone, but beyond that just about every other aspect of these cards is worse. Most contactless cards can be asked to transmit the cardholder's name, credit card number, and expiration date, and the card will happily do so, wirelessly. This is often enough to make fraudulent online transactions. It's trivially easy to build a device that does this using a microcontroller and a coil of wire. You don't need to have a payment processor's encryption key, you can just make one up and the card will reply. You can walk around in a crowded area with such a device and capture responses from hundreds of cards in under an hour. Electronic devices that clone your contactless card are usually better, as they generally require some sort of interaction before they'll respond -- actual physical contactless cards might as well be a megaphone attached to your credit card number. If you can capture a genuine transaction between a POS terminal and a contactless card, and if the transaction amount is below the card's floor limit, the transaction can often be replayed or relayed to a different terminal. With a cheap amplifier, this can be done reliably from low single digit ft away. The floor limit is usually somewhere around $20-$100 below which the terminal doesn't ask for a PIN or go online.
- yarcob 5y ago
  > You can't clone a NFC card from RF alone You imply that it is possible to clone NFC cards with other means. Is that really possible? Crypto chips are usually hardened against all kinds of attacks, and I would assume that NFC cards are resistant to cloning even if you have physical access to the chip. I'd be curious to learn more about that if my assumption is incorrect. Regarding replay attacks, do you have a source on that? I would assume that even offline POS terminals would use a nonce to prevent replay attacks. Is that assumption incorrect? And finally, you can extract card holder name and card number from most cards just by looking at them. Claiming that NFC cards are somehow worse than mag stripe cards in that regard is just FUD.
  - ohazi 5y ago
    > You imply that it is possible to clone NFC cards with other means. Is that really possible? I mean, sure, it's always possible, but probing a secure microcontroller with needles and an electron microscope isn't really what I meant. I was referring to what the various mobile wallet applications do behind the scenes when they allow you to "import" a plastic card and then use it as a contactless payment source via your phone's NFC radio. They're not actually cloning the private key inside the card, they're using various banking APIs to ask for a new key that, for all intents and purposes, will act exactly like the key on the physical card. They're supposed to ask for extra info so that they're super ultra sure the person importing the card is the legitimate cardholder, but this is not always very thorough. What kind of info do they typically ask for? Numbers printed on the card that you can acquire wirelessly by accidentally bumping into someone. If you're lucky, they'll try to do two-factor via SMS or email with information that they have on file, but I've seen some that don't bother. > Regarding replay attacks, do you have a source on that? I would assume that even offline POS terminals would use a nonce to prevent replay attacks. Is that assumption incorrect? I worked on an EMV contact + contactless implementation several years ago, and at the time contactless replay attacks were easy to demonstrate. Things may have improved since then, but the protocol was not very good (supposedly due to constraints from early NFC cards that were small and anemic), and I think they would need to redo most of it and kill backwards compatibility to mitigate the risk completely. https://www.youtube.com/watch?v=e023wGfVaE0 https://www.youtube.com/watch?v=e023wGfVaE0 https://www.cs.bham.ac.uk/~tpc/Relay/ https://www.cs.bham.ac.uk/~tpc/Relay/ https://www.hackster.io/news/this-tiny-10-device-can-perform-nfc-payment-replay-attacks-5486d6ecc405 https://www.hackster.io/news/this-tiny-10-device-can-perform... https://link.springer.com/chapter/10.1007/978-3-319-39814-3_8 https://link.springer.com/chapter/10.1007/978-3-319-39814-3_... https://en.wikipedia.org/wiki/Contactless_payment#Security https://en.wikipedia.org/wiki/Contactless_payment#Security From what I can tell, there was a lot of discourse around these problems around 2015-2018. There were demonstrations and exploits galore. But the standards were already out and none of the banks or card issuers wanted to change anything. Security researchers got bored and moved on. I don't see any evidence that replay and relay attack vectors have been fixed, or that they aren't exploited in the wild, just that the banks seem to consider the risk acceptable. > And finally, you can extract card holder name and card number from most cards just by looking at them. Claiming that NFC cards are somehow worse than mag stripe cards in that regard is just FUD. So you'll let me rifle through your wallet and write down the card numbers and expiration dates? Would the average person let me do this? Of course they wouldn't, because basically everybody knows that they need to prevent random people from seeing the various numbers printed on their payment cards. Is the average person aware that I can capture these markings by "accidentally" bumping into their back pocket on the subway? It's not FUD, it's a (subtly?) different issue, one that the public largely doesn't understand yet. What's frustrating about contactless cards is that there isn't even a good solution once you do understand the problem. Metal shields sewn into your wallet only hide the problem. The card will still respond if you shoot enough energy at it, and you'll still be able to pick up the response if you have a sensitive enough receiver.

by yarcob 5y ago

ohazi 5y ago

You're correct that you can't easily clone an NFC card from RF interactions alone, but beyond that just about every other aspect of these cards is worse. Most contactless cards can be asked to transmit the cardholder's name, credit card number, and expiration date, and the card will happily do so, wirelessly. This is often enough to make fraudulent online transactions. It's trivially easy to build a device that does this using a microcontroller and a coil of wire. You don't need to have a payment processor's encryption key, you can just make one up and the card will reply. You can walk around in a crowded area with such a device and capture responses from hundreds of cards in under an hour. Electronic devices that clone your contactless card are usually better, as they generally require some sort of interaction before they'll respond -- actual physical contactless cards might as well be a megaphone attached to your credit card number. If you can capture a genuine transaction between a POS terminal and a contactless card, and if the transaction amount is below the card's floor limit, the transaction can often be replayed or relayed to a different terminal. With a cheap amplifier, this can be done reliably from low single digit ft away. The floor limit is usually somewhere around $20-$100 below which the terminal doesn't ask for a PIN or go online.

yarcob 5y ago
> You can't clone a NFC card from RF alone You imply that it is possible to clone NFC cards with other means. Is that really possible? Crypto chips are usually hardened against all kinds of attacks, and I would assume that NFC cards are resistant to cloning even if you have physical access to the chip. I'd be curious to learn more about that if my assumption is incorrect. Regarding replay attacks, do you have a source on that? I would assume that even offline POS terminals would use a nonce to prevent replay attacks. Is that assumption incorrect? And finally, you can extract card holder name and card number from most cards just by looking at them. Claiming that NFC cards are somehow worse than mag stripe cards in that regard is just FUD.
- ohazi 5y ago
  > You imply that it is possible to clone NFC cards with other means. Is that really possible? I mean, sure, it's always possible, but probing a secure microcontroller with needles and an electron microscope isn't really what I meant. I was referring to what the various mobile wallet applications do behind the scenes when they allow you to "import" a plastic card and then use it as a contactless payment source via your phone's NFC radio. They're not actually cloning the private key inside the card, they're using various banking APIs to ask for a new key that, for all intents and purposes, will act exactly like the key on the physical card. They're supposed to ask for extra info so that they're super ultra sure the person importing the card is the legitimate cardholder, but this is not always very thorough. What kind of info do they typically ask for? Numbers printed on the card that you can acquire wirelessly by accidentally bumping into someone. If you're lucky, they'll try to do two-factor via SMS or email with information that they have on file, but I've seen some that don't bother. > Regarding replay attacks, do you have a source on that? I would assume that even offline POS terminals would use a nonce to prevent replay attacks. Is that assumption incorrect? I worked on an EMV contact + contactless implementation several years ago, and at the time contactless replay attacks were easy to demonstrate. Things may have improved since then, but the protocol was not very good (supposedly due to constraints from early NFC cards that were small and anemic), and I think they would need to redo most of it and kill backwards compatibility to mitigate the risk completely. https://www.youtube.com/watch?v=e023wGfVaE0 https://www.youtube.com/watch?v=e023wGfVaE0 https://www.cs.bham.ac.uk/~tpc/Relay/ https://www.cs.bham.ac.uk/~tpc/Relay/ https://www.hackster.io/news/this-tiny-10-device-can-perform-nfc-payment-replay-attacks-5486d6ecc405 https://www.hackster.io/news/this-tiny-10-device-can-perform... https://link.springer.com/chapter/10.1007/978-3-319-39814-3_8 https://link.springer.com/chapter/10.1007/978-3-319-39814-3_... https://en.wikipedia.org/wiki/Contactless_payment#Security https://en.wikipedia.org/wiki/Contactless_payment#Security From what I can tell, there was a lot of discourse around these problems around 2015-2018. There were demonstrations and exploits galore. But the standards were already out and none of the banks or card issuers wanted to change anything. Security researchers got bored and moved on. I don't see any evidence that replay and relay attack vectors have been fixed, or that they aren't exploited in the wild, just that the banks seem to consider the risk acceptable. > And finally, you can extract card holder name and card number from most cards just by looking at them. Claiming that NFC cards are somehow worse than mag stripe cards in that regard is just FUD. So you'll let me rifle through your wallet and write down the card numbers and expiration dates? Would the average person let me do this? Of course they wouldn't, because basically everybody knows that they need to prevent random people from seeing the various numbers printed on their payment cards. Is the average person aware that I can capture these markings by "accidentally" bumping into their back pocket on the subway? It's not FUD, it's a (subtly?) different issue, one that the public largely doesn't understand yet. What's frustrating about contactless cards is that there isn't even a good solution once you do understand the problem. Metal shields sewn into your wallet only hide the problem. The card will still respond if you shoot enough energy at it, and you'll still be able to pick up the response if you have a sensitive enough receiver.