4 ms·

The card readers are processing transactions? Wouldn’t there be a giant mainframe doing that somewhere?

MBCook 4y ago
It’s a combination of both sides. It’s something like this: For EMV the terminal and the card generate a request, and send it to the payment processor/bank. They say yes/no and send back some stuff needed to complete the transaction. At this point there would be a hold on your card. The terminal and card verify that and finish things, preparing proof of the final transaction. That’s sent to the processor again who confirms the transaction took place. This is when the money is taken and the hold disappears. Final proof from the processor is sent back to the terminal so the system knows everything went through. Now you get your receipt.
- FearlessNebula 4y ago
  The nitty gritty of everyday things like this can be so interesting sometimes
  - MBCook 4y ago
    I learned a lot of neat stuff about this process and other things around it as a side benefit of some of the tasks I was given at a job. It was fun to learn, and to see how they solved some of the problems that would come up that you might not think about. Of course the side effect is you also learn just how insecure older CC tech was. I think almost everyone sort of notice that at this point, but once you start learning the details… it’s bad. Basically electronically writing down CC numbers like they might have in the ‘60s, assuming people are good and trustworthy.
PeterisP 4y ago
It's a bit tricky with different payment flows possible for all kinds of scenarios. While at some point the transaction will get to "a giant mainframe somewhere" to get processed, it may or may not be during the process that a customer sees. It may be a "online" transaction where it's essentially that the terminal prepares a transaction message, the chipcard signs it, and then forwards it to issuing institution for authorization (including but not limited to checking availability of funds); or it may be permitted, within certain limits and depending on configuration, to have the chipcard sign the transaction and then deliver it for processing some time later (e.g. at end of day) so that either you can enable transactions in places which do not have internet access, or simply for processing speed for small amounts, taking on some limited risk for customer convenience.

It’s a combination of both sides. It’s something like this: For EMV the terminal and the card generate a request, and send it to the payment processor/bank. They say yes/no and send back some stuff needed to complete the transaction. At this point there would be a hold on your card. The terminal and card verify that and finish things, preparing proof of the final transaction. That’s sent to the processor again who confirms the transaction took place. This is when the money is taken and the hold disappears. Final proof from the processor is sent back to the terminal so the system knows everything went through. Now you get your receipt.

FearlessNebula 4y ago
The nitty gritty of everyday things like this can be so interesting sometimes
- MBCook 4y ago
  I learned a lot of neat stuff about this process and other things around it as a side benefit of some of the tasks I was given at a job. It was fun to learn, and to see how they solved some of the problems that would come up that you might not think about. Of course the side effect is you also learn just how insecure older CC tech was. I think almost everyone sort of notice that at this point, but once you start learning the details… it’s bad. Basically electronically writing down CC numbers like they might have in the ‘60s, assuming people are good and trustworthy.

PeterisP 4y ago

It's a bit tricky with different payment flows possible for all kinds of scenarios. While at some point the transaction will get to "a giant mainframe somewhere" to get processed, it may or may not be during the process that a customer sees. It may be a "online" transaction where it's essentially that the terminal prepares a transaction message, the chipcard signs it, and then forwards it to issuing institution for authorization (including but not limited to checking availability of funds); or it may be permitted, within certain limits and depending on configuration, to have the chipcard sign the transaction and then deliver it for processing some time later (e.g. at end of day) so that either you can enable transactions in places which do not have internet access, or simply for processing speed for small amounts, taking on some limited risk for customer convenience.