# Gavin Andresen
# 2010-08-06 22:12:44
# https://bitcointalk.org/index.php?topic=737.msg7990#msg7990

Some random Friday afternoon brainstorming: could you print out bitcoins to function as user-created paper money? @p{par}

@p{(link}QR code@p{link)} could be used to encode a transaction hash and a transaction signature on a piece of paper (along with a human-readable amount).  A bitcoin client could print out coins that are in your wallet and marks them as "PRINTED" (so you don't accidentally spend them@p{--} there would probably be a way of recovering them in case the paper versions were lost or stolen, and they'd automatically get removed when the paper versions were spent). @p{par}

Give that piece of paper to a merchant connected to the Bitcoin network and they can scan it and transfer the coins into their wallet.  They should then destroy the paper, because that transaction is spent. @p{par}

Double-spending would be nearly impossible, because once you give the paper to the merchant you lose control over exactly when they submit it to the network to be verified. @p{par}

The only problem I see is how the merchant gives you your change.  The merchant could print out the change, but you'd have to trust that they were giving you valid, unspent coins, unless you have a device connected to the network that could verify them (but that's dumb, because if you do have such a device why bother with paper bitcoins?).  We trust merchants not to give us counterfeit dollars... I wonder if fear of loss of reputation would be enough to keep them honest when giving paper bitcoins as change... @p{par}