5 ms·

Contactless cards fail to recognise foreign currency

37 points by eksith 12y ago

Guvante 12y ago
How is the card supposed to know the limit in a foreign currency? The real question is whether the banks will accept the transaction.
- mey 12y ago
  It could simply deny transaction requests in foreign currency.
  - tormeh 12y ago
    That doesn't sound like something the EU would be glad to hear...
    - mey 12y ago
      What's worse, additional steps to validate the transaction via swipe or unlimited purchase side by changing currency? It's an insecure design, I'm suggesting a simply approach that doesn't require the card to be more intelligent about international financial markets and exchange rates in real time.
    - dwild 12y ago
      Set a limit for each currency and if it's not on that list, deny it.
      - Guvante 12y ago
        What about currency's that fluctuate? The rate can change a lot in the several years a card is in consumer hands.
  - TheLoneWolfling 12y ago
    Or, you know, it could simply not do financial transactions over wireless.
  - Guvante 12y ago
    Why? The only way it is going to post is if the bank accepts it. Since the card can't know the conversion rate "allow anything" is a perfectly reasonable action.
- zaroth 12y ago
  Bingo! They didn't test the back end system, but what happens is the conversion is done to local currency and seeing that it's greater than the limit, it's denied. A non-story.
  - lxgr 12y ago
    Exactly. They seem to overlook that there are rules for the merchant as well; high-value transactions without a CVM are almost certain to raise flags (or be denied right away) at the merchant acquirer.
Someone1234 12y ago
Contactless card transactions always struck me as bonkers. By the very nature of the system, there is nothing stopping an individual walking down the street and stealing whatever the cap is out of everyone's card. You then immediately use this "money" to buy gift cards, which you then sell on, turning the dirty money into clean money. By the time they have traced back the money to the gift card, you're long gone (you can also cross international borders a couple of times to make things difficult/slow). The fact banks shut down the Mythbusters' investigation into just how insecure contactless cards are really tells you everything you need to know. They know full well they are completely insecure, and they want to keep it hush hush. Now contactless phone transactions are secure, but contactless phone transactions require action from the user to confirm the transaction. If the plastic cards had you press a button to activate contactless-mode they would be fine too, but they don't... NFC is great technology that has a lot of uses. This is just a mis-use.
- eksith 12y ago
  For anyone wondering about the incident with the Mythbusters and banks, here's some context by Adam Savage : https://www.youtube.com/watch?v=-St_ltH90Oc https://www.youtube.com/watch?v=-St_ltH90Oc
- smackfu 12y ago
  The limited scan range is the main security. 2-6 cm is what I see quoted.
  - Someone1234 12y ago
    Hmmm: http://www.bbc.com/news/technology-24743920 http://www.bbc.com/news/technology-24743920
    - smackfu 12y ago
      Although that does sound like it's eavesdropping on the transaction, rather than picking up the card in your pocket.
    - 12y ago
sjwright 12y ago
This doesn't make sense. Why would any transaction occur in a foreign currency? If I use my Australian credit card to purchase a cup of coffee in the UK, the transaction occurs in pounds, not Australian dollars. The terminal never sees "foreign currency". It is the responsibility of Visa/MasterCard to perform currency conversion.
- cmsj 12y ago
  This isn't about the terminal. Your card, which sees itself as a payer of AUD, gets a request for a transaction in GBP. This research suggests it will authorize the transaction even if it is above whatever normal local limit you have on AUD transactions. Whether that's actually true or not, is unknown at this stage - this was a test on a UK contactless card, so maybe we have a slightly different arrangement than your Australian contactless card would. It's also fairly unlikely that the payment processors would accept a transaction higher than the contactless cap, just because it's in a foreign currency. It's also entirely possible that they don't bother enforcing a limit because the UK banks involved won't accept any foreign currency contactless transactions. I've never tried to use my UK contactless cards abroad.
mcv 12y ago
First time I heard about contactless transactions I wondered if people never learned. Apparently they don't. Allowing anyone to take my money without my explicit approval, even if it's only up to 20 pounds at a time, is simply begging to be abused. I don't understand how anyone could possibly have thought this was a good idea.
lxgr 12y ago
The research paper seems to grossly oversimplify the matter of "cashing in" the fraudulent transactions. While the authors claim to "appreciate that banks will have a number of security systems in place to prevent fraud", they seem to neglect that those systems should effectively render the attack impossible: - There are limits for CVM-less transactions; not only in the application running on the chip, but also for terminals. I think that there is one limit above which a CVM (e.g. PIN or signature) is required, and another limit for offline authorizations. CVM-less high-vale transactions would not only be suspicious, but even non-compliant for most card schemes. - It is not trivial to apply for a merchant account, and I guess that a new account would not be allowed to immediately withdraw recently acquired funds. (If it were that simple, magnetic stripe card skimmers could simply apply for a merchant account and avoid all the hassle with PIN skimming, finding vulnerable merchants or ATMs etc.) - A merchant with a higher than average rate of transactions challenged by cardholders will surely be scrutinized even more closely. All in all, the implemented failure mode of offline-authorizing all transactions in unknown currencies seems like a really bad idea and should be improved. The rest of the paper seems like speculation, though. (Compare e.g. to Steven J Murdoch's work ("Chip and PIN is broken" etc.), where the claims have been verified with an actual payment terminal.)

37 points by eksith 12y ago

How is the card supposed to know the limit in a foreign currency? The real question is whether the banks will accept the transaction.

mey 12y ago
It could simply deny transaction requests in foreign currency.
- tormeh 12y ago
  That doesn't sound like something the EU would be glad to hear...
  - mey 12y ago
    What's worse, additional steps to validate the transaction via swipe or unlimited purchase side by changing currency? It's an insecure design, I'm suggesting a simply approach that doesn't require the card to be more intelligent about international financial markets and exchange rates in real time.
  - dwild 12y ago
    Set a limit for each currency and if it's not on that list, deny it.
    - Guvante 12y ago
      What about currency's that fluctuate? The rate can change a lot in the several years a card is in consumer hands.
- TheLoneWolfling 12y ago
  Or, you know, it could simply not do financial transactions over wireless.
- Guvante 12y ago
  Why? The only way it is going to post is if the bank accepts it. Since the card can't know the conversion rate "allow anything" is a perfectly reasonable action.
zaroth 12y ago
Bingo! They didn't test the back end system, but what happens is the conversion is done to local currency and seeing that it's greater than the limit, it's denied. A non-story.
- lxgr 12y ago
  Exactly. They seem to overlook that there are rules for the merchant as well; high-value transactions without a CVM are almost certain to raise flags (or be denied right away) at the merchant acquirer.

Someone1234 12y ago

Contactless card transactions always struck me as bonkers. By the very nature of the system, there is nothing stopping an individual walking down the street and stealing whatever the cap is out of everyone's card. You then immediately use this "money" to buy gift cards, which you then sell on, turning the dirty money into clean money. By the time they have traced back the money to the gift card, you're long gone (you can also cross international borders a couple of times to make things difficult/slow). The fact banks shut down the Mythbusters' investigation into just how insecure contactless cards are really tells you everything you need to know. They know full well they are completely insecure, and they want to keep it hush hush. Now contactless phone transactions are secure, but contactless phone transactions require action from the user to confirm the transaction. If the plastic cards had you press a button to activate contactless-mode they would be fine too, but they don't... NFC is great technology that has a lot of uses. This is just a mis-use.

eksith 12y ago
For anyone wondering about the incident with the Mythbusters and banks, here's some context by Adam Savage : https://www.youtube.com/watch?v=-St_ltH90Oc https://www.youtube.com/watch?v=-St_ltH90Oc
smackfu 12y ago
The limited scan range is the main security. 2-6 cm is what I see quoted.
- Someone1234 12y ago
  Hmmm: http://www.bbc.com/news/technology-24743920 http://www.bbc.com/news/technology-24743920
  - smackfu 12y ago
    Although that does sound like it's eavesdropping on the transaction, rather than picking up the card in your pocket.
  - 12y ago

sjwright 12y ago

This doesn't make sense. Why would any transaction occur in a foreign currency? If I use my Australian credit card to purchase a cup of coffee in the UK, the transaction occurs in pounds, not Australian dollars. The terminal never sees "foreign currency". It is the responsibility of Visa/MasterCard to perform currency conversion.

cmsj 12y ago
This isn't about the terminal. Your card, which sees itself as a payer of AUD, gets a request for a transaction in GBP. This research suggests it will authorize the transaction even if it is above whatever normal local limit you have on AUD transactions. Whether that's actually true or not, is unknown at this stage - this was a test on a UK contactless card, so maybe we have a slightly different arrangement than your Australian contactless card would. It's also fairly unlikely that the payment processors would accept a transaction higher than the contactless cap, just because it's in a foreign currency. It's also entirely possible that they don't bother enforcing a limit because the UK banks involved won't accept any foreign currency contactless transactions. I've never tried to use my UK contactless cards abroad.

mcv 12y ago

First time I heard about contactless transactions I wondered if people never learned. Apparently they don't. Allowing anyone to take my money without my explicit approval, even if it's only up to 20 pounds at a time, is simply begging to be abused. I don't understand how anyone could possibly have thought this was a good idea.

lxgr 12y ago

The research paper seems to grossly oversimplify the matter of "cashing in" the fraudulent transactions. While the authors claim to "appreciate that banks will have a number of security systems in place to prevent fraud", they seem to neglect that those systems should effectively render the attack impossible: - There are limits for CVM-less transactions; not only in the application running on the chip, but also for terminals. I think that there is one limit above which a CVM (e.g. PIN or signature) is required, and another limit for offline authorizations. CVM-less high-vale transactions would not only be suspicious, but even non-compliant for most card schemes. - It is not trivial to apply for a merchant account, and I guess that a new account would not be allowed to immediately withdraw recently acquired funds. (If it were that simple, magnetic stripe card skimmers could simply apply for a merchant account and avoid all the hassle with PIN skimming, finding vulnerable merchants or ATMs etc.) - A merchant with a higher than average rate of transactions challenged by cardholders will surely be scrutinized even more closely. All in all, the implemented failure mode of offline-authorizing all transactions in unknown currencies seems like a really bad idea and should be improved. The rest of the paper seems like speculation, though. (Compare e.g. to Steven J Murdoch's work ("Chip and PIN is broken" etc.), where the claims have been verified with an actual payment terminal.)