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How do you use stored credit card info if the cc# is not stored? Unlike passwords, the encryption for the cc#s has to be reversible. That's part of the reason

by ak217 16y ago

How do you use stored credit card info if the cc# is not stored? Unlike passwords, the encryption for the cc#s has to be reversible. That's part of the reason why they introduced CVCs, right?

jimktrains2 16y ago
You could at least have them encrypted on disk with a key only stored in memory, i.e.: when the system is turned on. Alternatively a dedicated crypo device where you feed it cipher text and it gives you plain text would also help as the attack wouldn't be able to get the key (even if they have the physical box (for good crypto devices)) While only marginally better depending on the type of attack and permissions gained by the attacker, if all they got was static data on disk, then it would be secure.
- cookiecaper 16y ago
  And what if that server needs to be rebooted some day? What if there's a hardware failure and it has to be powered off? Something as big as PSN has multiple servers reading the same DB and must be able to tolerate failures without forcing everyone to re-enter their CC #. The keys must be stored persistently somewhere.
  - tzs 16y ago
    What we do where I work is take the newly generated key whenever we key or rekey the system, split it into multiple pieces using Shamir's secret sharing algorithm, and those pieces are distributed to several people. Whenever the server needs to be started, two of those people must enter their key shares. That enables the server to reconstruct the key, which is then stored in memory.
  - jimktrains2 16y ago
    As tzs said, you basically have to have someone(s) restart the system and re-enter they key.
Terretta 16y ago
> How do you use stored credit card info if the cc# is not stored? Simplifying just a bit -- The one time you pass the # along to the bank, they give you back a transaction ID you can use to do future things with that card. The bank knows the number, looks it up by that ID.

by ak217 16y ago

How do you use stored credit card info if the cc# is not stored? Unlike passwords, the encryption for the cc#s has to be reversible. That's part of the reason why they introduced CVCs, right?

jimktrains2 16y ago

You could at least have them encrypted on disk with a key only stored in memory, i.e.: when the system is turned on. Alternatively a dedicated crypo device where you feed it cipher text and it gives you plain text would also help as the attack wouldn't be able to get the key (even if they have the physical box (for good crypto devices)) While only marginally better depending on the type of attack and permissions gained by the attacker, if all they got was static data on disk, then it would be secure.

cookiecaper 16y ago
And what if that server needs to be rebooted some day? What if there's a hardware failure and it has to be powered off? Something as big as PSN has multiple servers reading the same DB and must be able to tolerate failures without forcing everyone to re-enter their CC #. The keys must be stored persistently somewhere.
- tzs 16y ago
  What we do where I work is take the newly generated key whenever we key or rekey the system, split it into multiple pieces using Shamir's secret sharing algorithm, and those pieces are distributed to several people. Whenever the server needs to be started, two of those people must enter their key shares. That enables the server to reconstruct the key, which is then stored in memory.
- jimktrains2 16y ago
  As tzs said, you basically have to have someone(s) restart the system and re-enter they key.

Terretta 16y ago

> How do you use stored credit card info if the cc# is not stored? Simplifying just a bit -- The one time you pass the # along to the bank, they give you back a transaction ID you can use to do future things with that card. The bank knows the number, looks it up by that ID.