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You cannot overdraw your account because your computers clock is wrong. You cannot overdraw your account because there is an issue with a credit card terminal

You cannot overdraw your account because your computers clock is wrong. You cannot overdraw your account because there is an issue with a credit card terminal around clock sync. This simply cannot happen. If it can, let me suggest that whoever is writing the account debit code wrap the balance check and debit in a transaction. You can easily stick a rackmount atomic clock in your data center. NTP can source from a variety of sources. There are digital RADIO time signals. On a given exchange, again, you can still trade stocks. Folks forget that there used to be open outcry trading. Even without that an order book can be operated successfully without GPS. Credit card terminals do not require clock sync with GPS links, they do not have GPS antennas in most cases. If they need precise time, they can timestamp when going through authorization steps to approve the transaction. It's weird, as someone I guess older, the new generation seems to build such fragile system and think only such ultra complex systems are usable. Yes, things like Google's Spanner are cool. Yes, performance would degrade without GPS (maybe - I can think of some work arounds). But not everyone needs globally distributed consistent databases. You'd be surprised at how much of banking, stock exchange work does NOT depend on anything like these tools. I wish the HN comments would focus on the many pretty obvious options one could deploy if GPS went away if you even believed that the current system means your bank account will be overdrawn because of a lack of GPS.

dogma1138 5y ago
No one said you can overdraw your account but the terminal would simply refuse to connect or the transaction would be rejected by the server due to clock sync issues. Also no one said that the terminals get a GPS signal either but if the clock is off on them vs the server they will fail, I have worked on a lot of payment systems. Rackmount atomic clocks still need a GPS signal today to be set or they have to be pre-set in a central location and then distributed. Time syncing used to be a PITA and now it’s easy due to GPS so pretty much every protocol has a very narrow time tolerance. My work HP laptop drifts 3-5 min over the weekend of the VPN because it’s not set to an external time server and all hell breaks loose. Yes civilization will not end over night but it would have a major impact we will find ways to get by but there will be havoc and the financial damages will be in the trillions heck the disruption to shipping and logistics alone would be immense nearly every one and every thing today is reliant on GPS either directly or indirectly.
- whoknowswhat11 5y ago
  > No one said you can overdraw your account False: The qz article I'm responding to says this. "When you pull cash from an ATM or swipe your card at the coffee shop, the machine needs to determine the precise time that the transaction occurs to, for example, prevent it from being over-drawn." Please please explain how this "over-drawn" situation occurs because of a GPS satellite. > but if the clock is off on them vs the server they will fail, I have worked on a lot of payment systems. False, CC terminal clocks do not need to be GPS time accurate. When the terminal connects to authenticate, they can update their time. There can be issues with authentication if clock skew is bad, but this requires normal levels of time sync (ie, NTP without GPS will be fine).
  - dogma1138 5y ago
    While the reason is not necessarily correct (although it’s more of an over simplification than an outright error) the terminal needs to have the correct time if not the transaction would not be processed for a myriad of reasons. The issue is that in the vast chain of networks that a single transaction flows through you have multiple NTP servers each of them taking their own time form a different source which is often backed by GPS. If GPS services are disrupted globally this would cause payment networks to break down. Yes there would be a way to recover from it and move away from GPS but you are still missing the point on day-0 of a GPS blackout the global financial system would go down and it would be a mess and it wouldn’t be a mess that is easily sorted…

dogma1138 5y ago

No one said you can overdraw your account but the terminal would simply refuse to connect or the transaction would be rejected by the server due to clock sync issues. Also no one said that the terminals get a GPS signal either but if the clock is off on them vs the server they will fail, I have worked on a lot of payment systems. Rackmount atomic clocks still need a GPS signal today to be set or they have to be pre-set in a central location and then distributed. Time syncing used to be a PITA and now it’s easy due to GPS so pretty much every protocol has a very narrow time tolerance. My work HP laptop drifts 3-5 min over the weekend of the VPN because it’s not set to an external time server and all hell breaks loose. Yes civilization will not end over night but it would have a major impact we will find ways to get by but there will be havoc and the financial damages will be in the trillions heck the disruption to shipping and logistics alone would be immense nearly every one and every thing today is reliant on GPS either directly or indirectly.

whoknowswhat11 5y ago
> No one said you can overdraw your account False: The qz article I'm responding to says this. "When you pull cash from an ATM or swipe your card at the coffee shop, the machine needs to determine the precise time that the transaction occurs to, for example, prevent it from being over-drawn." Please please explain how this "over-drawn" situation occurs because of a GPS satellite. > but if the clock is off on them vs the server they will fail, I have worked on a lot of payment systems. False, CC terminal clocks do not need to be GPS time accurate. When the terminal connects to authenticate, they can update their time. There can be issues with authentication if clock skew is bad, but this requires normal levels of time sync (ie, NTP without GPS will be fine).
- dogma1138 5y ago
  While the reason is not necessarily correct (although it’s more of an over simplification than an outright error) the terminal needs to have the correct time if not the transaction would not be processed for a myriad of reasons. The issue is that in the vast chain of networks that a single transaction flows through you have multiple NTP servers each of them taking their own time form a different source which is often backed by GPS. If GPS services are disrupted globally this would cause payment networks to break down. Yes there would be a way to recover from it and move away from GPS but you are still missing the point on day-0 of a GPS blackout the global financial system would go down and it would be a mess and it wouldn’t be a mess that is easily sorted…