Regarding the private, offline payment, there has been a somewhat comparable, actually offline, system in place in Germany for the last 30 or so years: https://

Regarding the private, offline payment, there has been a somewhat comparable, actually offline, system in place in Germany for the last 30 or so years: https://en.wikipedia.org/wiki/Geldkarte https://en.wikipedia.org/wiki/Geldkarte Probably due to its security being based on the security of the embedded smart card, it had a much lower limit and other than my father showing me how it worked 20 years ago I have neither used nor seen anybody use it.