9 ms·

While we're on the subject of Japanese vending machines, how do they implement the IC card scanning feature? Does it need to be connected to a special network o

While we're on the subject of Japanese vending machines, how do they implement the IC card scanning feature? Does it need to be connected to a special network or is the logic all done on the card? I'm specifically talking about the payment verification and logic. I have one in my office that accepts IC card payment and I'm not quite sure what is required for that to work.

shidoshi 9y ago
Suica, Pasmo and the like are all contactless SCs. The Wikipedia page is a good start, and you can go deeper from there: https://en.wikipedia.org/wiki/Suica https://en.wikipedia.org/wiki/Suica
- bschwindHN 9y ago
  Ah sorry, I mean how the machine verifies the validity of the card.
  - sly010 9y ago
    It's asymmetric key cryptography. Every vending machine can verify signatures using a CA certificate. Charging stations and a vending machines also have a signing key signed by that central certificate. Whatever is written on the card is signed by whoever wrote it. Charging a card goes like this: - Read everything from the card (data + signature) - Verify signature + expiration dates, etc - Extract amount on card - Decrement said amount - Write new amount to card - Sign data on card using local signing key It's a bit more complicated than that, but you get the idea. In some systems the logs of all transactions are reconciled asynchronously (if and when internet connection is available) so if a card is cloned it can eventually be detected and blocked.
    - bschwindHN 9y ago
      The "local signing key" is the interesting part to me. I guess only vending machines in certain areas can get IC card support. I wonder how often those local keys need to be rotated. That's a great answer though, thanks for writing it up!
eaeertae 9y ago
adsfg afaf asdf asdf dsf f fas df
iand675 9y ago
I'm not entirely sure, but yesterday I observed some vending machines at a local university that worked with student IDs. The machines had a small antenna encased in the drink display, so presumably that model broadcast payment and/or inventory updates to some nearby receiver or via stock WiFi networks. I'd expect that there would be a strong incentive to have the cards require network access to verify balances or else some enterprising hackers could potentially reverse engineer the process to add additional funds to the card.

shidoshi 9y ago

Suica, Pasmo and the like are all contactless SCs. The Wikipedia page is a good start, and you can go deeper from there: https://en.wikipedia.org/wiki/Suica https://en.wikipedia.org/wiki/Suica

bschwindHN 9y ago
Ah sorry, I mean how the machine verifies the validity of the card.
- sly010 9y ago
  It's asymmetric key cryptography. Every vending machine can verify signatures using a CA certificate. Charging stations and a vending machines also have a signing key signed by that central certificate. Whatever is written on the card is signed by whoever wrote it. Charging a card goes like this: - Read everything from the card (data + signature) - Verify signature + expiration dates, etc - Extract amount on card - Decrement said amount - Write new amount to card - Sign data on card using local signing key It's a bit more complicated than that, but you get the idea. In some systems the logs of all transactions are reconciled asynchronously (if and when internet connection is available) so if a card is cloned it can eventually be detected and blocked.
  - bschwindHN 9y ago
    The "local signing key" is the interesting part to me. I guess only vending machines in certain areas can get IC card support. I wonder how often those local keys need to be rotated. That's a great answer though, thanks for writing it up!

eaeertae 9y ago

adsfg afaf asdf asdf dsf f fas df

iand675 9y ago

I'm not entirely sure, but yesterday I observed some vending machines at a local university that worked with student IDs. The machines had a small antenna encased in the drink display, so presumably that model broadcast payment and/or inventory updates to some nearby receiver or via stock WiFi networks. I'd expect that there would be a strong incentive to have the cards require network access to verify balances or else some enterprising hackers could potentially reverse engineer the process to add additional funds to the card.