A laptop, running unconnected to a power cord (on battery), using high-quality disks of some sort.
How would you hack that? Short of breaking into where it's set up, I don't see how.
How are you getting information on and off that?
Because if you don't have any way to do so, that device is useless.
Unless you plan on having a person manually enter all the data (which still opens you up to social engineering attacks), you are going to be using some device to transfer data, and that device can be hacked.
USB drives and even floppies can contain viruses.
And there are some ways to get information across that air gap.
What you need is a faraday cage to encapsulate that computer, ideally surrounded by something giving off lots of random noise.
This would not be environmentally friendly at all.
The best way to stop that is to shut the door.
No it isn't.
That is like saying some foods could poison you and cause you to throw up. The best way to stop that is to seal your mouth shut so you can't eat ever, causing your death.
In reality, selecting the best way involves understanding the risks of each option and the consequences of them, including flow on effects.
I could very easily design a computer system to do just that, if I had a computer engineer.
You mean you could come up with a bunch of requirements with no concern for the actual implementation of it.
Implement offline redundancy by making a secure core system which can then transfer to delivery systems. That is, if all gas stations are on the same system, you have a system that will backup without being hacked. And ideally, you have a few of these, in case one fails.
How?
How is this system backed up? How does it transfer?
2. Cut out all these "data centers." Environmentally, they are bloated by constantly being online like that. They use alot of heating and cooling that wouldn't be used by a constant update data load. Our neighboring town for instance is getting its water stolen for a data center. It is far more resource intensive to try to manage that information online than to have local updates which are manually logged each day. It's also more secure.
Data centres can be more environmentally friendly than the alternative.
It needs to be built to handle the maximum load, not a constant load.
A data centre allows different companies to share resources so each can handle their peak load, which moves between different companies.
3. Make secure (if possible, underground) facilities for such data. The harder it is to locate such an area, the harder more physical (such as Ethernet or RF signals) hacks are to do.
And such facilities would require a lot for cooling.
The infrastructure around it will likely give it away.
4. Make an ID chip for these computers. Make the system based on this for upload. The data cannot be updated except one way. Meaning an asshole/idiot cannot tamper from their computer, only the person with that computer hardware can log in and change things. With the same password, any other computer will not login.
And then if the ID chip is lost or damaged, all the data is as well.
But that ID chip is effectively just a fancy password anyway.
You have the possibility of that chip being stolen or cloned, or just the technology behind it being circumvented.
Also, this is effectively what is already used by SSH.
For SSH you generate keys, a private key which should be stored securely on your computer, and a public key which goes to the device you want to access.
That private key is used just like your chip to prove you are allowed to access the computer. But there are flaws with the implementation which sometimes allows other people to get in.
So other than these being made as chips, we already have this technology, and know its limitations.
What makes you think your chip will be magically perfect, and not suffer from any of the flaws of SSH?