Printed bitcoins / fast transactions

[commlinx]

This is just a random thought I had over a beer, so I promise to take it well if someone points out it's retarded / impossible / already been discussed .

If I want to head to the pub for a few beers and pay with BTC and see in their advertisement a beer is 0.5BTC I could send them coins in advance and maybe they could give me coupons for the beer, or send me coins back for what I didn't drink etc. But it's a bit less convenient than printed notes and what if I feel like a pizza on the way home? I might have my phone on me but those buttons get small when you're 3 parts pissed .

I was thinking in printed form the coin (which would likely really be a note) could have the private key of a wallet, but a newly generated one that only contained the face value. Because printing the notes well in advance is convenient / likely it would already be confirmed, so then the only problem would be a double-spend by two copies being in existence, but it could be backed by a verification network that took a hash of the key and another random number (also printed on the note) so it didn't have much to do and could quickly verify that the note should exist, and then mark it as spent in a second.

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[Pieter Wuille]

www.bitbills.com

[commlinx]

Cool. That is similar to what I was thinking of but I'd envisaged everyone would print their own. I guess your idea adds a level of physical security (much like a banknote) and makes a double-spend less likely, but it comes at the cost of some hassle like added charges and needing to order in advance and get it physically delivered etc.

[Meni Rosenfeld]

You can print your own if the bar is properly equipped. Put exactly 0.5 BTC in an address and print a QR-code of its private key. You give it to the bar, they scan it, claim the coins and give you a beer. They might also be willing to give you the beer in advance, and sort it out later if it turns out you gave them a fake.

Unlike bitbills, they will have to claim it on the spot, they can't keep it for future use as a note.

[steelhouse]

I was thinking have a bill that is a dollar bill in size.  On it have Edward Griffin, Ron Paul, Bill Still, Jim Rogers, and Peter Schiff.  Then have a code for wallet that contains say 1 BTC.  You make this dollar yourself on your laser printer.  It is no good until scanned then become worthless.  But I think in the real world you might need change with copper, silver, nickle.

[commlinx]

I was thinking have a bill that is a dollar bill in size.  On it have Edward Griffin, Ron Paul, Bill Still, Jim Rogers, and Peter Schiff.  Then have a code for wallet that contains say 1 BTC.  You make this dollar yourself on your laser printer.  It is no good until scanned then become worthless.  But I think in the real world you might need change with copper, silver, nickle.

Not sure if you're taking the piss or not, but what Meni posted above is the basic idea I had for low value transactions. As he said would have to be processed straight away and couldn't be saved. I'm not sure change is always required, in my example you might have a good idea before you leave a beer is 0.5BTC, and if a pizza is 2.9BTC you probably wouldn't be too worried about giving a 0.1BTC a tip, or could carry a few smaller denominations if you were.

[Ryland R. Taylor-Almanza]

http://bitcoin.modernjob.info/print.html