furio on Nostr: So Alice has a phone (this is the acquiring device) and tries to pay for coffee at a ...

So Alice has a phone (this is the acquiring device) and tries to pay for coffee at a merchant (Bob's Coffee). The offline "device" is Alice's phone? The acquiring device is some third "acquiring agent" that has to do with nostr (nostr safebox)?

If true, a user could have a home (online) lightning node, and keep a key to use the node on a phone that needn't be online, and spend by just (somehow secretly) passing the key to the coffee merchant?

Could cashu stored on nostr locked by a private key also do the same thing, a lot easier? Offline I could keep ecash tokens on my phone, which is one way. Or I could store them on relays (as private notes) and unlock them (with a private key app on my phone (could be offline)), and send them to the merchant.