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> how do you prove that you can spend the received funds? You prove it by producing a partial signature for the transaction (a transaction essentially requires

• tsimionescu 5y ago
  > You prove it by producing a partial signature for the transaction (a transaction essentially requires a multisig by both sender and receiver). Oh, ok, I misunderstood what this meant. > You couldn't send it twice because the transaction consumes an input utxo. Paying twice would require two different transactions with two different multisignatures. This assumes the receiver is trust-worthy, that they counter-sign the transaction if it was accidental. So if I accidentally pay twice for a single item, the seller can just sign both transactions and send me only one item, and I can't do much about it. Of course, they can also send 0 items, which is why blockchains can't secure transactions in a useful sense - you need the law and insurance and other social mechanisms for that.