Printing bitcoins : could it work?

[em3rgentOrdr]

or you could just hand them a $20 bill...

QR codes that you can print on your computer is the way to go.

http://delivr.com/qr-code-generator  
(I also mesaged them and asked for bitcoin to be added to their list of services)

I put a btc address in the following qr code lol

AWESOME!!!  Turns out there are a whole variety of these QR code scanners for all brands of cell phones...  http://delivr.com/11gru.  I just installed i-nigma for iPhone with realtime scanning for Free on my iPhone, pointed my iPhone at your image on my computer screen, and it instantly recognized the QR code as:

1MG2EaHRBnL4FPuy2Wu752ZGaqNeyuJ9aJ

Could you verify if this is correct?  I will send you a bitcoin in a few minutes...please verify if you receive them.  If so, we can mark September 11, 2010 as the first day in history that bitcoins were exchanged by scanning a QR code of a bitcoin address! 

One you receive my bitcoin, feel free to return it back to me  at the my bitcoin address below:



Thanks!

[jgarzik]

QR-code should decode to something like

      bitcoin://17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j

because there are plenty of non-bitcoin QR-code users out there too.

[theymos]

QR-code should decode to something like

      bitcoin://17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j

because there are plenty of non-bitcoin QR-code users out there too.

Zarutian wrote a proposed Bitcoin URI scheme for this kind of thing, and I made some modifications. Here it is:
http://pastebin.com/VsBbmXQx

According to that, you would use something like:
x-btc:addr=1NXYoJ5xU91Jp83XfVMHwwTUyZFK64BoAD?theymos;store
This says "Store 1NX... in your address book under the label 'theymos'".

[LZ]

I think that using URI is the right way. You may test my QR Code too.



P.S. I found online QR Code decoder: http://zxing.org/w/decode.jspx

[Anonymous]

or you could just hand them a $20 bill...

QR codes that you can print on your computer is the way to go.

http://delivr.com/qr-code-generator  
(I also mesaged them and asked for bitcoin to be added to their list of services)

I put a btc address in the following qr code lol

AWESOME!!!  Turns out there are a whole variety of these QR code scanners for all brands of cell phones...  http://delivr.com/11gru.  I just installed i-nigma for iPhone with realtime scanning for Free on my iPhone, pointed my iPhone at your image on my computer screen, and it instantly recognized the QR code as:

1MG2EaHRBnL4FPuy2Wu752ZGaqNeyuJ9aJ

Could you verify if this is correct?  I will send you a bitcoin in a few minutes...please verify if you receive them.  If so, we can mark September 11, 2010 as the first day in history that bitcoins were exchanged by scanning a QR code of a bitcoin address!  

One you receive my bitcoin, feel free to return it back to me   at the my bitcoin address below:



Thanks!

I just noticed this today and nearly fell off my chair lol



I sent the coin back to you 

[em3rgentOrdr]

I just noticed this today and nearly fell off my chair lol



I sent the coin back to you 

Great!  I got that coin back from you yesterday!  Now I would like to try something else: send a bitcoin wallet as qr code.  Below is the qrcode for a bitcoin wallet.dat (of size 45 bytes) containg .05 bitcoins encoded as a string of lowercase hexadecimal characters:



Please decode that image, export the string of hexadecimal characters (using your favorite hex editor) into a bitcoin wallet.dat, run your bitcoin client with this wallet.dat file, and try to send that .05 bitcoins out of it to your own address.  Tell me if it works.

I suppose this "offer" is first come first serve to whoever can decode this wallet and extract the .05 bitcoins...

I hope I'm not forgetting some other necessary information that I need to provide you other than this wallet.dat file?

[LZ]

It seems broken. There are 46 bytes, but not 45.
Should we try to inject it to the existing wallet.dat?
Also I think that we should use UUE/MIME encoding.
But wallet even compressed XZ can't fit in QR Code.

[jgarzik]

A QR-code of a wallet isn't going to be very useful to a lot of people.

More useful is to make a QR-code represent a database entry at PrintedBitcoins.com.  Then anyone may redeem the QR-code for bitcoins, even if they do not have a bitcoin client.

[em3rgentOrdr]

It seems broken. There are 46 bytes, but not 45.
Should we try to inject it to the existing wallet.dat?
Also I think that we should use UUE/MIME encoding.
But wallet even compressed XZ can't fit in QR Code.

ok, my bad...I guess what I thought was my wallet wasn't a real wallet...somehow got corrupted.

Ok.  Let me try printing an actual entire bitcoin file.  Here are my steps: I started with a fresh client (with full block chain), got .05 bitcoins from the bitcoin faucet, waited for 8 confirmations, stopped my bitcoin client, compressed my 16kb wallet.dat file into a 6kb wallet.dat.gz, outputted that compressed wallet.dat.gz as a string of hexadecimal bytes (big nibble first, little nibble second) seperated by spaces (od -t x1 -A n wallet.dat.gz), then removed the spaces and returns from that using sed so that I now have a 12kb text file of hex bytes, then I split that 12kb file into six 2kb files (using split -b 2048), and then I used iec16022 -f PNG to convert each of those six 2kb hex files into six DataMatrix images below:








now this bitcoin wallet (containing the measly sum of .05 bitcoins) can be decoded by scanning those files with a DataMatrix decoder, and then reversing all the steps above to obtain the wallet.dat file.  Then swap your current wallet.dat file with this wallet.dat file and see if the bitcoins are present.  If so, then you can extract the bitcoins out of them by sending them to your own bitcoin address.

A QR-code of a wallet isn't going to be very useful to a lot of people.

More useful is to make a QR-code represent a database entry at PrintedBitcoins.com.  Then anyone may redeem the QR-code for bitcoins, even if they do not have a bitcoin client.

Well I disagree.  One of the reasons we want to print bitcoins is to avoid having to connect to the network or deal with computers at that moment, to deal with bitcoins in person-to-person without having to have electronics, to deal with bitcoins in case of temporary network disconnection, to safely store your bitcoin wallet in a non-electronic format incase of long-term power-outage/natural disater, and other reasons as has been discussed earlier in this forumn.  So it seems that some people would very much find it useful to print out their wallet.

Anyway, first-come-first-serve to whoever can extract the .05 bitcoins out of that wallet.

Also, what is the best way using linux to output a binary file into something that can most effectively be encoded by QRcode or DataMatrix?  How exactly would I use UUE/MIME encoding (i.e. what command would I type in linux to format a wallet.dat binary file)?

[bitwaffle]

Think you need online verification to prevent me from printing 2 copies of my wallet and double spending it. Who ever makes it back first to the scanner wins. Even an online database has the same problem... if I am relying on a paper token, it can always be copied and double spent.

[em3rgentOrdr]

Think you need online verification to prevent me from printing 2 copies of my wallet and double spending it. Who ever makes it back first to the scanner wins. Even an online database has the same problem... if I am relying on a paper token, it can always be copied and double spent.

Yes.  I understand this.  But as has been talked about earlier in this forum, paper bitcoins are great if you are dealing offline with someone you trust:

It all comes down to how much you trust the entitiy you are transacting with.

If I'm paying the kid mowing my lawn in Bitcoin 'notes' I know I'm honest. If there is some problem we can sort it out when he comes back next month.
If I'm buying my groceries from 'Big Grocery Store' (BGS) they will be doing online transaction processing to verify my Bitcoin notes are valid before I leave the store, and I can trust that the notes they are printing me for my change will be valid.
If I'm borrowing 10BTC from my friend, he can pass a note from the BGS to me because I can trust he he's not double spending it. The note can proceed down the chain of trust.

If I'm buying a DVD from a guy on a street corner, he might not be inclined to take my bitcoin note (unless he has an iPhone to check the transaction is valid) and I'll probably want to use exact change, because I'm not going to trust any notes he gives me in return.

Bitcoin notes are a great solution when you are:

a) Offline
b) Dealing with someone you trust.

It also doesn't prevent you choosing to use some other method.
It just provides you with an extra option. Which is a Good Thing.

[em3rgentOrdr]

I think that using URI is the right way. You may test my QR Code too.



P.S. I found online QR Code decoder: http://zxing.org/w/decode.jspx

Oh, btw, I just sent you a bitcoin to your QR-encoded address for your wasted effort trying to get that .05 bitcoins out of my corrupted wallet file.

[em3rgentOrdr]

OK!  I have thought of a new idea: use self-destructing messages to hold the wallet containing the bitcoins.  And basically the printed part that you carry around in your pocket (outside of visible light) is the printed QR code of the url for that self-destructing message.  Now of course real self-destructing messages only exist in quantum computation, but there are a variety of free internet services that will store messages that will destruct whenever the first person reads them: http://www.google.com/search?q=self+destructing+message.  Anyway, I have put 10 bitcoins in the self-destructing message you can access only once by decoding this QR code below, going to the encoded URL, copying the hex codes from the self-destructing message into a wallet.dat.gz file, uncompressing that .gz file, swap it with your regular wallet file, start your client, send the 10 bitcoins to your own address, and restart the client with your regular wallet file.  Ok!?  Anyone can give it a try and report your success by decoding this QR code below:

[LZ]

Someone took this wallet, but did successfully decode it?

[TTBit]

If printed bitcoins were created, I would use them. Please keep up the good work.

I would use it to print out 100 BTC notes on 3x5 index cards and stash them away in a fire proof box/safety deposit box for safe keeping. Software would be needed to print/decode/verify the coins and forward to my wallet when needed.

I understand I can probably do this with a thumbdrive, but for a non-techie, there is a relaxing feeling of actually holding a physical something with a number on it. I am terrified of moving around my wallet file, especially if I had 1000+ coins on it.

[WARlrus]

I believe that the way forwards with this may still be to have a central authority responsible for holding the money - as a bank would do.

Been having a think about how this could work, and here's what I've come up with...

Getting printed money

• User deposits BitCoins on an online system
• User selects quantity of BC that they want to generate a note for
• System generates QR code containing hash of transaction, and gives the user a printable/saveable note

Purchasing

• User goes to shop and pays with BC note
• Shop scans QR code, and passes the hash to the bank (via an open API)
• Bank checks if that note has been redeemed before (IE is still valid), and returns the response
• Shop accepts/rejects payment accordingly
• Shop can either keep the note, or redeem it

Redeeming

• User scans QR code and passes hash to the bank along with a BC address to pay to
• Bank checks if note has been redeemed
• Bank makes payment to given address

Does this sound like a system people would want to use? If so, I might be persuaded to write a website to handle such a process!

[nelisky]

Purchasing

• User goes to shop and pays with BC note
• Shop scans QR code, and passes the hash to the bank (via an open API)
• Bank checks if that note has been redeemed before (IE is still valid), and returns the response
• Shop accepts/rejects payment accordingly
• Shop can either keep the note, or redeem it <-- The only way to be safe is to redeem on check availability, otherwise the user can take a copy of the note elsewhere

[TTBit]

Purchasing

• User goes to shop and pays with BC note
• Shop scans QR code, and passes the hash to the bank (via an open API)
• Bank checks if that note has been redeemed before (IE is still valid), and returns the response
• Shop accepts/rejects payment accordingly
• Shop can either keep the note, or redeem it <-- The only way to be safe is to redeem on check availability, otherwise the user can take a copy of the note elsewhere

Kinda like when I go to the horse races? I have winning tickets that can be used to bet against, and a machine just gives me back a credit voucher (my change). There are thousands of old tickets lying on the ground, but everyone knows these are worthless. Doesn't seem too difficult if thought of this way.

[jgarzik]

I believe that the way forwards with this may still be to have a central authority responsible for holding the money - as a bank would do.

Yes, that is the central thesis behind this forum thread,
http://bitcointalk.org/index.php?topic=739.0

[WARlrus]

The only way to be safe is to redeem on check availability, otherwise the user can take a copy of the note elsewhere

Yup, I just thought of that. There's nothing to stop the user creating multiple copies of a note, so it would have to be checked and redeemed straight away.

Would that be a problem?

And the question stands - would anyone actually use this?