5 ms·

What authorization token? If you mean the CVV it isn't required to make a transaction.

by tjoff 8y ago

gruez 8y ago
>If you mean the CVV it isn't required to make a transaction. that's incorrect. there's a cvv1 on the magstripe that's needed for magstripe transactions, and there's cvv2 that's on the back of the card that's mostly required (depends on merchant policy) for card not present transactions. for EMV transactions, you need a payment terminal because the card will refuse to communicate unless the other side has a valid certificate. even then, the card only returns a signed response, which you can't use elsewhere.
- tjoff 8y ago
  > that's incorrect. No? You just said so yourself? "depends on merchant policy" Why would an attacker choose a merchant whose policy denies their use case? Why would an attacker opt for a magstripe transaction or a contactless transaction?
  - gruez 8y ago
    >No? You just said so yourself? "depends on merchant policy" Why would an attacker choose a merchant whose policy denies their use case? it's not as easy as you think. nearly all merchants require some sort of additional information (cvv, billing address, cardholder name) in addition to card number + expiration date. reason being, for card not present transactions (eg. online), the merchant is liable for fraud (the purchase amount + ~$25 chargeback fee), so they have a strong financial incentive to collect/verify as many pieces of information to reduce their losses. it would be insane to not collect any of those (only requiring card number + expiry date), because the chargebacks will bankrupt you. the reason i said "depends on merchant policy" is because some merchants (iirc amazon) don't collect cvv2 (but they do collect billing address + cardholder name), which I presume is for convenience/conversion rate reasons. I don't actually know of any merchants that only collects card number + expiry date.
    - tjoff 8y ago
      Sure, forgot that name wasn't provided. But name is the only additional information you need to make a legitimate purchase, and that information isn't a secret (if you, under any circumstance, ask for someones CVV they will tell you to fuck off. Ask for their name is another thing (maybe even present on a name tag or in many cases trivial in a certain context)). It will make it slightly harder to just randomly scan peoples pockets on the subway but still an absolute security nightmare. Just disable NFC altogether, no reason not to.
      - gruez 8y ago
        >But name is the only additional information you need to make a legitimate purchase where did you get the impression that there are merchants (worth stealing from) that only accepts card number + expiry + name? the example I gave was with amazon, and they take name AND address. even if you're able to find a merchant with lax security and is worth stealing from, how long can you keep the scam up for? maybe a week or two before the fraud reports start pouring in? then they'll patch up their systems and you're back to square one. you're better off installing skimmers and using the card numbers at any merchant that accepts credit (at least in the US). >will make it slightly harder to just randomly scan peoples pockets on the subway but still an absolute security nightmare. considering that you have to be pretty close for NFC to work, whoever is doing it is going to look pretty suspicious as he's bumping into everyone walking endlessly through the train. >Just disable NFC altogether, no reason not to. I can think of one: convenience. wave your card in front of the reader vs insert card, wait, type in, wait some more, then taking out your card.
        tjoff 8y ago
        Do amazon really even validate the address to the card owner? I've sent stuff to different locations in different names using the same card. I've heard poker and gaming sites are popular to extract funds (and simultaneously launder them), don't expect them to have much security no. > considering that you have to be pretty close for NFC to work, whoever is doing it is going to look pretty suspicious as he's bumping into everyone walking endlessly through the train. Seriously? Just go during rush hour and you can basically stand still, the victims will practically bump into you for you. I don't expect anyone to attempt sprinting a carriage at a time...

What authorization token? If you mean the CVV it isn't required to make a transaction.

by tjoff 8y ago

What authorization token? If you mean the CVV it isn't required to make a transaction.

>If you mean the CVV it isn't required to make a transaction. that's incorrect. there's a cvv1 on the magstripe that's needed for magstripe transactions, and there's cvv2 that's on the back of the card that's mostly required (depends on merchant policy) for card not present transactions. for EMV transactions, you need a payment terminal because the card will refuse to communicate unless the other side has a valid certificate. even then, the card only returns a signed response, which you can't use elsewhere.

tjoff 8y ago
> that's incorrect. No? You just said so yourself? "depends on merchant policy" Why would an attacker choose a merchant whose policy denies their use case? Why would an attacker opt for a magstripe transaction or a contactless transaction?
- gruez 8y ago
  >No? You just said so yourself? "depends on merchant policy" Why would an attacker choose a merchant whose policy denies their use case? it's not as easy as you think. nearly all merchants require some sort of additional information (cvv, billing address, cardholder name) in addition to card number + expiration date. reason being, for card not present transactions (eg. online), the merchant is liable for fraud (the purchase amount + ~$25 chargeback fee), so they have a strong financial incentive to collect/verify as many pieces of information to reduce their losses. it would be insane to not collect any of those (only requiring card number + expiry date), because the chargebacks will bankrupt you. the reason i said "depends on merchant policy" is because some merchants (iirc amazon) don't collect cvv2 (but they do collect billing address + cardholder name), which I presume is for convenience/conversion rate reasons. I don't actually know of any merchants that only collects card number + expiry date.
  - tjoff 8y ago
    Sure, forgot that name wasn't provided. But name is the only additional information you need to make a legitimate purchase, and that information isn't a secret (if you, under any circumstance, ask for someones CVV they will tell you to fuck off. Ask for their name is another thing (maybe even present on a name tag or in many cases trivial in a certain context)). It will make it slightly harder to just randomly scan peoples pockets on the subway but still an absolute security nightmare. Just disable NFC altogether, no reason not to.
    - gruez 8y ago
      >But name is the only additional information you need to make a legitimate purchase where did you get the impression that there are merchants (worth stealing from) that only accepts card number + expiry + name? the example I gave was with amazon, and they take name AND address. even if you're able to find a merchant with lax security and is worth stealing from, how long can you keep the scam up for? maybe a week or two before the fraud reports start pouring in? then they'll patch up their systems and you're back to square one. you're better off installing skimmers and using the card numbers at any merchant that accepts credit (at least in the US). >will make it slightly harder to just randomly scan peoples pockets on the subway but still an absolute security nightmare. considering that you have to be pretty close for NFC to work, whoever is doing it is going to look pretty suspicious as he's bumping into everyone walking endlessly through the train. >Just disable NFC altogether, no reason not to. I can think of one: convenience. wave your card in front of the reader vs insert card, wait, type in, wait some more, then taking out your card.
      - tjoff 8y ago
        Do amazon really even validate the address to the card owner? I've sent stuff to different locations in different names using the same card. I've heard poker and gaming sites are popular to extract funds (and simultaneously launder them), don't expect them to have much security no. > considering that you have to be pretty close for NFC to work, whoever is doing it is going to look pretty suspicious as he's bumping into everyone walking endlessly through the train. Seriously? Just go during rush hour and you can basically stand still, the victims will practically bump into you for you. I don't expect anyone to attempt sprinting a carriage at a time...