http://sparrowa7io5pz6ud3ehqzosvepbxbxt2zphmkjsylp2zgxooko23pqd.onion/docs/spending-privately.html
But what if we want to pay someone non-interactively (that is, without asking them for a fresh address every time)?
For that to work in a private manner, we need to get a unique identifier for the recipient we can use to create fresh addresses.