combine with a central authority server network and make it blind signatures and you have untraceable e-cash.
E-cash depends on the secrecy of the signed data, and immediate redemption with the issuer once it's been spent/accepted. This is a terrible model for physical cash.
> immediate redemption with the issuer once it's been spent/accepted. This is a terrible model for physical cash
also the obvious way such cash would work is that "redemption" is just the new minting of coin. the central authority will mint a new coin by blindly signing your secret after you "destroy" the spent coin by giving them the unblinded signature.
> That's really neat! Seems potentially adaptable to paper currency--a verifiable QR code digital signature of the bill's serial number creates a cryptographically hard obstacle to counterfeiting!
I don't see how any e-cash solutions can help here.
It's just much "too private" to get any political traction. At the very least, I suspect an acceptable modern alternative would either have caps on what can be sent/received completely anonymously (e.g. per recipient and timespan) or want non-anonymous recipients (to allow for VAT/sales tax accounting etc.)