The necessity of making change is major usability/privacy/fungibility roadblock that shows up in more than just cash. For example, it presents a problem for cha

The necessity of making change is major usability/privacy/fungibility roadblock that shows up in more than just cash. For example, it presents a problem for chaumian e-cash or other private money systems like pre-MLSAG monero. If it's possible to do the equivalent of cash, but with some sort of smartcards that exchange some sort of offline zero-knowlege proofs, then that would be preferable over physical cash, because it could eliminate the need for change or marked bills and it would be even more private.