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Comment by chii | Hacker News Reader

> that the "money you have" is just an int32

well, luckily, that's not how money is stored, but instead, they're transaction based. Aka, that number you have is a calculated value, not a stored, arbitrary value.

Except...perhaps the central bank's, where they could really just generate that money as an arbitrary value to lend out to other banks.

footnote: of course, your account balance is cached, so that it is not recalculated over and over again...

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Alas, no matter how the bits that makes up my bank balance looks, in practice its still a single point of failure where I might simply lose access to my money if the right service is down. Cash has much better uptime stats, even if it can be inconvenient to carry around.

Do you know of any resources where I can read about how banks store digital currency? Would be interesting to see how international transactions are handled, if they chunk data into months/periods, etc.

I can't say this is exactly what you're after, but this article is really interesting https://calpaterson.com/bank-python.html

Similar to what the author describes, I wouldn't be surprised if a lot of this information is generally not public.

I'm a banker. What you're looking for here is called "interbank clearing". In europe that would be SEPA[1]

But yes, most clearing is done daily. Each bank basically submits their daily flow of money to each other participating bank, and the central ACH (Automated Clearing House) keeps track of the balances. There's some processes in there by which banks can dispute charges, which is super interesting, but also way to complicated for me to detail here.

[1]: https://www.europeanpaymentscouncil.eu/what-we-do/epc-paymen...

Side question, but what happens if there's a technical error with the service provider that leads to double spending?

Example: we bought tickets worth 300 EUR from Deutsche Bahn, they were hit by a DDoS and couldn't complete the transaction.

We got charged *twice* (i.e. 600 EUR and not refunded yet. AND no tickets!!!

Now they claim all they can do is to give us 600 EUR in vouchers (that are not even transferrable).

Would a Chargeback work in this case?

And my friend (who's ordered the tickets) has a very traditional bank that only gives a statement monthly, and probably accepts claims on every 29 of February, between 7 and 8 AM and only by fax (IYKYK those German companies...)

Thank you! Will read up on this.

> well, luckily, that's not how money is stored, but instead, they're transaction based.

Not really. That's how the accounting works. It's the gold standard, and what we guarantee our customers, it's not universally how we store it though. Plenty of bank systems store just singular balances and infer that back into "transactions" in other systems to make the balance even out. Then the errors in those balances are manually corrected by looking at the sums.

IT systems only rarely match the legal frameworks they operate within.

Regular banks create new money all the time (loans). There’s no difference to the central bank conceptually as far as I understand, they both record debits/credits to accounts (double entry).

Ah yes, who needs the Federal Reserve when you have Kansas' own Emprise Bank.

Seems like a distinction without difference in this context. The result of the "what is account x's current/available balance" is still some integer or decimal number.

But the GP implied that the bank (or someone) could just alter that number, and it would become reality.

I'm saying that this can't be done - at least, not without leaving such a large trail behind that it would be easily reverted, and relevant people prosecuted.

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