Lets imagine the Fed start registering digital USD for use in offline e-wallets, and they figure out a way to make it so that only registered wallets can make transactions.
Without an online
centralized server validating and tracking ownership of currency to a wallet, I would worry that hackers could theoretically dupe money.
I know that each time that currency changes wallets, the transaction would need to be signed into the currency.
But what about in cases where there is a dupe (Double-spending) of that currency from the same state?
Could a digital currency function even temporarily offline?
Theoretical safeguards like unhackable wallets and a currency unit having to 'check-in' online after a certain amount of time before it can change hands again, and things like that are ok to assume. Just because whatever-coins haven't done it yet doesn't mean it can't be done.
But from an info-sec perspective, what are some ways to prevent/detect fraud in offline digital currency transactions?