Why is it useless? You need to pay a single user so you can just mint some cashu for him and be sure he is the only receiver... No trustparties involved in.. that is the main problem that is the solution... Simple and direct!
Discussion
But why would you print that on a paper bill?
Cause someone could take them everywhere without a connection and could share them offline
But you don't know the receiver's pubkey before you leave the house...
I'm just saying that securing with a receiver pubkey and paper ecash don't seem to go hand in hand 😅
No problem.. you could tied it after you receive it.. you generate the token in a wallet and share on the paper 😎