Tentatively, I would say that is 'easy'. Easy because the necessary smart card technology has existed for decades, and because almost every smartphone now retailing includes Near-Field Communication features and smart card chips already. Although early smart cards had some security flaws (as would be expected in the early days of widespread civilian encryption), these no longer apply to modern smart cards.
I bought a day pass for the Brussels city transport system at a ticket machine last month, and the machine simply loaded and dispensed a smart card for me to use immediately on any bus, tram or train. This shows that smart cards are not only cheap, they can be literally disposable!
Therefore I would say that is 100% a policy issue: all it would take is one country or large city to implement digital cash with the legal and functional constructs to ensure anonymous transactions and your dream would come true.
I bought a day pass for the Brussels city transport system at a ticket machine last month, and the machine simply loaded and dispensed a smart card for me to use immediately on any bus, tram or train. This shows that smart cards are not only cheap, they can be literally disposable!
Therefore I would say that is 100% a policy issue: all it would take is one country or large city to implement digital cash with the legal and functional constructs to ensure anonymous transactions and your dream would come true.