Wanted: Application to print your own Bitcoin Money

[brendio]

I've been thinking about the issue of the current need for portable wallet technology to spend bitcoin at point of sale locations, such as Meze Grill. I present here my idea for critique and possible application from someone with the required knowhow to implement. My idea is a combination of Bitbills, Cassius's paper wallets and the metal engraved cards. My idea focuses not so much on security so much as portability. The idea is an application that would allow one to print their own Bitcoin keypairs (and even better, corresponding QR codes) to make single-use paper Bitcoin currency is various demoniations (e.g. 1, 0.5, 0.1, 0.05 BTC etc.)

What I envisage is a program that can print the key pairs off the grid if required and print either directly to a printer of via a pdf file. Ideally, you would be able to use a template for print the paper money on to standard sized sheets, such as perforated business card printer sheets. You could make it such that you fold the card to hide the private key and seal it with a tamper-evident sticker, but leave the public key and QR code linked to the block explorer address visible, as well as having the denomination value printed on the card. Basically, it is a home made Bitbill, but without the extra security features.

Then, either the program or the user loads the card by sending bitcoins from the user's wallet to the paper money address.

Since I've made and loaded the money myself, I don't need to trust a third party keeping a copy of the private key. I do however, need to keep the paper money physically secure, just like the other money in my wallet.

Now when I go to a restaurant and need to pay my bill, I just hand over the required amounts of paper Bitcoin money to the owner, who then reveals then private key and transfers the balance to his account. I could also keep a card in my physical wallet with an address of my own for receiving change if I don't have the exact change in paper money.

Would anyone be interested in implementing such a solution?

Please understand what this is and isn't supposed to be. This is a means to make Bitcoin as portable as paper money without needing to carry a laptop or smartphone to make a payment (okay, the merchant still need technology, so it is perhaps more akin to a prepaid debit card). This is not meant for storing large amounts of Bitcoin, only for what you would ordinarily carry in your physical wallet. This is not meant for people receiving the Bitcoin paper money to be able to spend again. It is for single use only, as the recipient has no way to know that you have not kept a copy of the private key and can spend it before they redeem it. This is intended to be lower cost than BitBills, and available in any desired value.

Addendum: The major problem with implementing such a system right now is the inability of the standard client to import key pairs. So a useful interim solution would be a website running siba's patch that allows you to input a private pair and make a transaction to another Bitcoin address. This could then be used by the merchant to redeem the paper Bitcoin money.

[Stephen Gornick]

Addendum: The major problem with implementing such a system right now is the inability of the standard client to import key pairs.

Wouldn't instawallet do 99.5% of this?

An example of a service built on top of InstaWallet
 - http://forum.bitcoin.org/index.php?topic=24452.0

[bitfreak!]

Here's a better idea:

 A website where you deposit BTC and in return you get a code which is linked to those funds. So that code can basically be redeemed on the same website by anyone. The code doesn't even need to be physcially written down onto paper, it could be saved into your phone too.

But both methods have the same problems. Anyone can easily create fake codes/notes and pretend they are real. Like you say, they will need to have the necessary technology. So it's viable for businesses who will most likely always have internet access, but not for small trades between people.

Put simply, you cant use the bitcoin codes/notes like normal money, which requires no verification because the notes are hard enough to forge that people assume it is going to be real if it looks real.

[brendio]

Here's a better idea:

 A website where you deposit BTC and in return you get a code which is linked to those funds. So that code can basically be redeemed on the same website by anyone. The code doesn't even need to be physcially written down onto paper, it could be saved into your phone too.

Actually, you could make a series of Instawallets, encode their urls to to a QR code, and print the QR code with the denomination on it. Load them up as in my OP, and then just hand them over. The merchant can scan them in on their computer/mobile device and immediately transfer the value out to their account for payment. Much simpler than my original idea.

I'm aware of the problems you mention, but thought I made it clear in my post that the purpose of this was an easy way to carry paperlike Bitcoin money without needing technology as a customer and without having to load your wallet or potentially expose you login detail to an ewallet on the merchants computer (might be running a keylogger for all you know).

[david4dev]

It looks like someone has at least started a project to do exactly this. It's called paper-keys. I haven't tested it myself, but it looks like a good start.

[brendio]

Thanks for the link. Looks like I'm not the first to have the idea. Will try it out.

[TheRandomGuy]

/???This is very interesting...