How does eCash solve the double-spending problem in an offline environment? I'm not comfortable just trusting the payer.
📍In areas without internet or banking access, we use solutions that meet local needs, like those built on the Cashu protocol.
💡With this tech, offline transactions are possible, like this child buying a donut with SATs at an onboarded shop. 🍩⚡️nostr:npub12rv5lskctqxxs2c8rf2zlzc7xx3qpvzs3w4etgemauy9thegr43sf485vg nostr:npub1f0rtesc8yd8utjhpgktlltv4t2rftxd5kmkagt5kymt8946pqf7qe90snx
#Bitcoin_for_unbanked
https://blossom.primal.net/ccb20c9477b9a2744a8f11ad2de17d3f4b66b4068e10d479a131246a915f0f61.mp4
Discussion
You redeem with the mint (internet) as soon as you’re able as the receiver.
if you're the merchant and have Internet, you don't need to trust anyone. the payer can remain offline.
generally, one party having internet is enough to prevent double spending
also this is a surprisingly common situation throughout the world
merchant has internet, customer does not
yes, merchant usually doesn't move, customer does!
the opposite could also exist, tho probably less common:
vending machine (offline) - customer mobile (online)
in that case, customer/sender can create offline verifiable tokens
This was a specific design goal for my Bitcoin Deposits proposal. Always-online vault pays an invoice based on onion message for the invoice and max fee signed by the deposit private key. Potentially a single NFC tap by an offline customer
This is going to take off unbelievably in Africa, we haven't seen anything yet.