Now regimes blockade, censor, or simply disable the internet.
In such places only 'paper' currency or 'barter' currency (Au,Ag,?) has value.
We need a cash that needs no internet.
That means a piece of 'paper/plastic/ceramic' that physically cannot possibly be counterfeited. According to quantum mechanics such a beast could be fabricated.
As a matter of mathematical and physics, we already do exactly that whenever we cast a brick or print paper or ?: In a quantum perspective anything we create is utterly unique.
Yes, this gets weird in microseconds. Imagine for a moment you could buy a 'scrying stone' which would decrypt the quantum appearance of a coin reflecting a specific laser light.
A "coin" would have a specification written on it that, under a specific light, reflection would yield a specific pattern through a 'standard' 'scrying stone'. True Magick.