Printing bitcoins : could it work?

[Gavin Andresen]

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

QR code 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-- 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).

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.

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.

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...

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[NewLibertyStandard]

What you would want to do is act as a bitcoin reserve. You print paper money which promises to be redeemable for bitcoins by you. And you promise to keep those bitcoins reserved. If the person spending and accepting the paper money trust you, it would work fine.

[jgarzik]

Sure, printing bitcoins could work

I just posted a proposal for bitcoin checks, including source code and a printable PDF example, in the " [RFC] bitcoin electronic check standard" thread:
http://bitcointalk.org/index.php?topic=739.0

[MoonShadow]

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

QR code 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-- 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).

I see problems already.

First, there are no crypto-objects in your wallet that could actually be called coins.  You could, at best, print out a 2d scancode that represents the signed transfer chain, but you would still need an address first.  You would need some kind of bitcoin bank reserve willing to issue traditional banknotes or checks. 

[NewLibertyStandard]

I only glanced at the check idea, so this might be the same thing, but you could theoretically send the amount of bitcoins that you want to spend to yourself and then write the private key on a piece of paper. Anyone who knows that private key can spend the money, so the check would need to be kept private. It would not be safe to let your cashier accept them since he or she could secretly steal them and say that they had already been spent.

[hugolp]

Maybe this has future, who knows.

But I really think that using smartphones to make payments with bitcoin is a more comfortable way of doing things. Printing paper is a thing of the past.

[jimbobway]

in most casinos there is a printer in all the slot machines that print out what money you have left. there is a barcode on the piece of paper where u can put it into another slot machine or go to a casino teller and exchange it for cash. so I think such a concept is feasible since casinos already somewhat have such a system.

[skull88]

Maybe this has future, who knows.

But I really think that using smartphones to make payments with bitcoin is a more comfortable way of doing things. Printing paper is a thing of the past.

My idea too, just type in the amount on your smartphone, type in the adress, cashier can see instantly the payment and done.
I don't see why we need paper bitcoins and deal with al the troubles involved with it, printing, scanning, trust,... and it isn't eco friendly.

So I go for smartphone or maybe card, paper bitcoins doesn't have a future imho, but I can be wrong offcourse.

[RHorning]

I remember reading about something like this almost twenty years ago in a Byte magazine article about electronic money.  The concept at the time was in reference to "e-mailing" a debit transfer through a hash/cryptographic process which is in principle a concept similar to printing money on paper.

The trick here is to set up some system that would prevent a double spending of the money.  Once that is solved, the rest is fairly mechanical and simple to accomplish.

I should note here that checks can and have been used as a medium of exchange in the past too, treated literally as a "bank note" in the same fashion that other more direct "bank notes" like most fiat currencies have been accepted.  The reputation and trust of the individual who wrote the check was the deciding factor for acceptance of the check.  Early Renaissance era merchants commonly used checks instead of currency for a great many transactions, and it was common for a check to go through the hands of hundreds of people before it finally landed at the bank for redemption.  That is a bit more unusual today, where most checks usually get cashed out immediately, or a second generation at best.  A noted exception would be for autograph hunters that may value the autograph more than the value of the check.

Here is a technical question on the topic:  Is there a way to "spend" bitcoins to some hash address that could be verified as "available" (not recovered or claimed) and put both the private and public keys for claiming that money onto some piece of paper or to be transmitted through some lightweight protocol medium like e-mail, FTP, or even a simple thumb drive?

This is essentially setting up a "wallet" (in the Bitcoins sense) that would hold the value of the "money" being printed, where the wallet is backed up onto paper and you are in essence handing all of the information for that entire wallet over to some other person.  They would then have the option of transferring all of the money in that wallet to their own wallet, or using that "money" in some way and handing it over to a 3rd person as a separate transaction.  Once the money is transferred out of the wallet, the information about that wallet could then be discarded.

Am I missing something here, of would that work?  It really would be the bitcoins equivalent to actual printed money, and for the paranoid you could easily verify that the coins really are in that wallet.  A really paranoid merchant could "destroy" the wallet and re-issue the currency in fresh newly minted bitcoin certificates to their customers if they were making change... with the trust being strictly the integrity of the merchant alone and the relationship between the customer and the merchant.

Somebody being foolish (or stupid) and printing out multiple certificates with the same information would have their reputation tarnished when somebody tries to examine the contents of this wallet only to discover there is no value in there.  Some might claim that the wallet was hacked, but the presumption would be that the person was trying to double-spend bitcoins.

I like this as it turns money back into a personal relationship experience.  If you don't trust a stranger (or they are somebody who you know has scammed you in the past), you still can go back to the network to verify that the value of the money is real.  But it can be a way to remove the electronic overhead for small value transactions on day to day purchases.  Carrying around such a certificate would be no different than carrying around current government-issued money in a physical wallet.

[RHorning]

My idea too, just type in the amount on your smartphone, type in the adress, cashier can see instantly the payment and done.
I don't see why we need paper bitcoins and deal with al the troubles involved with it, printing, scanning, trust,... and it isn't eco friendly.

So I go for smartphone or maybe card, paper bitcoins doesn't have a future imho, but I can be wrong offcourse.

The problem with a smartphone or some other gadget is that there is overhead involved in trying to get the device to carry out the transaction.  Yes, it could be done, but what happens when the networks are shut down temporarily, or you are in a situation where access to electronics is limited.  Not everybody has 24/7 access to a network even in industrialized western nations.

I would also have to be convinced on the eco-friendly aspect of this too.  You can print out quite a bit of paper for it to have the same environmental impact as the production of an iPhone.  You are also burning up a fair bit of coal for simply operating that device, or causing other sorts of environmental damage.

Also, all trade of any kind is a matter of trust between the customer and the merchant.  The question is how to reduce the threshold where distrust prevents a trade from happening.  If you are in a situation where large numbers of Bitcoins (in terms of value) need to be transferred or if you really don't trust either the merchant or the customer, you would need something a bit more complex for the transfer.  That is where cashier's checks and other more secure fiscal instruments are used even in today's business world.

If you have the smartphone, I would say go for it, but this idea of "paper bitcoins" and variations on the theme have a niche application where a smartphone isn't strictly needed.  Dismissing completely out of hand the idea that you could make paper bitcoins doesn't really resolve the issue as to if it is is possible or practical.

[hugolp]

As I said previously, maybe this idea could work, who knows, let the people who want to use it decide, but in my opinion is not a good idea. This is why:

The problem with a smartphone or some other gadget is that there is overhead involved in trying to get the device to carry out the transaction.  Yes, it could be done, but what happens when the networks are shut down temporarily, or you are in a situation where access to electronics is limited.  Not everybody has 24/7 access to a network even in industrialized western nations.

Well, a smartphone has mobile internet connection (almost) everywhere in a industrialized nation. Also, the shop could have a wifi or bluetooth connection to allow for the phone to connect and make the payment. And you dont need to have a bitcoin server in the phone, you could have a frontend that connects through ssh to you home bitcoin server and orders payments. You can even have the objects tagged with 3D barcodes that allows the phone to recoignaze them and the customer does not even have to type anything into the phone, just scan the barcodes with its phone and confirm the transaction.

Or this idea I just came up with: Imagine bitcoind would have a webpage frontend where you could order it to make payments (obviously password protected). The shop would only need to let you access your server webpage and make the payment.

Arent all this options simpler that printing paper?

I would also have to be convinced on the eco-friendly aspect of this too.  You can print out quite a bit of paper for it to have the same environmental impact as the production of an iPhone.  You are also burning up a fair bit of coal for simply operating that device, or causing other sorts of environmental damage.

I dont think people is going to decide if they own an iPhone depending on its capability as a bitcoin wallet.

Also, all trade of any kind is a matter of trust between the customer and the merchant.  The question is how to reduce the threshold where distrust prevents a trade from happening.  If you are in a situation where large numbers of Bitcoins (in terms of value) need to be transferred or if you really don't trust either the merchant or the customer, you would need something a bit more complex for the transfer.  That is where cashier's checks and other more secure fiscal instruments are used even in today's business world.

If you want a middle man that the merchant could trust there alredy exists internet bitcoin accounts.

If you have the smartphone, I would say go for it, but this idea of "paper bitcoins" and variations on the theme have a niche application where a smartphone isn't strictly needed.  Dismissing completely out of hand the idea that you could make paper bitcoins doesn't really resolve the issue as to if it is is possible or practical.

Again, we'll see what happen. Maybe it does have some use, I just dont see it.

[HostFat]

I think that Bitcoin has to add a new way to sign coins, something like "without-owner". ( a new sign in the protocol )

1) An user ( A ) ask the Bitcoin client to make a QR-code ( or a like ) of 100 Bitcoins ( it's an example )
2) Bitcoin client cut 100 Bitcoins from the A user's wallet, and signs them ( 100 bitcoins  ) with the new sign "without-owner", and generate the QR-Code of this operation.
3) User B will be able to check the QR-Code to see if these 100 bitcoins ( he will also find that they are "100" bitcoins ) are still signed "without-owner" or not, and he can chose to own them or not.

[dwdollar]

The masses will demand paper, regardless of whether we consider it outdated or foolish.  I think it's a good idea to have a redeemable note and/or check if we want Bitcoin to be available to them.  How it should work I don't know.

[RHorning]

Arent all this options simpler that printing paper?

No.  Imagine if you have a kid mowing your lawn.  In that case I think it would be much easier to hand him a bitcoin certificate for his work than trying to demand that he has bluetooth or a wireless device to receive the payment for services rendered.  

The idea of a web front-end with password protection is even less secure (by a huge degree... and opening up the potential for that merchant to wipe out all of the money you now or in the near future will have) than simply handing over a cryptographically secure "wallet" or "wallets" with a predetermined and small amount of bitcoins of roughly the amount needed to conduct the transaction.

Mind you, this doesn't necessarily have to be done with physical objects.  You could "e-mail" bitcoins in this manner to somebody who doesn't even have a Bitcoin node running, where they could even "redeem" the bitcoins for government-issued money straight away without even getting directly involved with Bitcoins.  As an alternative, the bitcoins could simply be in a thumb drive instead where you could transfer over the files to the merchant representing the bitcoins you wish to use for the purchase, and they could even return the "change" to you in a similar fashion.

All in all, what you are suggesting here is far and away more complex than this paper currency system I'm suggesting here, and has been originally discussed at the start of this thread.  This is a very lightweight bitcoin transfer system that has electronics of any kind as an optional aspect, and can enable purchases even if network access is unavailable on a temporary basis.

What keeps people honest here is that the values can be verified, and double spending is minimized through the verification process.  Somebody who is double spending is committing fraud, which has existing legal implications.  If they obtained those bitcoin certifications from a 3rd party, a legal investigation of fraud would then target that person who created those bogus bitcoin certificates in the first place.

Also, don't get caught up in the technical details.  A 3-D bar code is there only to enable a higher density of information, not necessarily that it is superior to a 2-D or even 1-D (like a UPC symbol) bar code.

I would also have to be convinced on the eco-friendly aspect of this too.  You can print out quite a bit of paper for it to have the same environmental impact as the production of an iPhone.  You are also burning up a fair bit of coal for simply operating that device, or causing other sorts of environmental damage.

I dont think people is going to decide if they own an iPhone depending on its capability as a bitcoin wallet.

That is handwaving off the idea.  I'm just saying that the environmental friendly aspect is not nearly as clear-cut as was previously indicated and shouldn't be a rationale for dismissing this idea.  It shouldn't even really play a part in this discussion, and to me is more of a wash in terms of potential environmental damage rather than a reason not to use this system.

Also, all trade of any kind is a matter of trust between the customer and the merchant.  The question is how to reduce the threshold where distrust prevents a trade from happening.  If you are in a situation where large numbers of Bitcoins (in terms of value) need to be transferred or if you really don't trust either the merchant or the customer, you would need something a bit more complex for the transfer.  That is where cashier's checks and other more secure fiscal instruments are used even in today's business world.

If you want a middle man that the merchant could trust there alredy exists internet bitcoin accounts.

This is more than just a middle man, and this system doesn't require a 3rd party to be involved in the first place.  You create the "bitcoin certificate" from BTC you already have, and present that to a merchant or whomever you need to pay in terms of services or products rendered.  The purpose here is to provide a very simple and technologically lightweight system for payments using bitcoins.

If you have the smartphone, I would say go for it, but this idea of "paper bitcoins" and variations on the theme have a niche application where a smartphone isn't strictly needed.  Dismissing completely out of hand the idea that you could make paper bitcoins doesn't really resolve the issue as to if it is is possible or practical.

Again, we'll see what happen. Maybe it does have some use, I just dont see it.

For you, I think this would take a very direct and physical demonstration of the concept to convince you that it could work.  It would never be something that I would be comfortable in terms of a purchase of an automobile or a house, but if I went to a local farmer's market and handed over a 5 BTC note to buy a bag of apples, that would be an almost ideal application of this "technology".

As I also hinted at above, this would also be a way to expand the number of Bitcoin users in a rather substantive way where they wouldn't necessarily have to be generating coins to join into the network, or even have a need to generate the coins.  A bitcoin certificate would be a great way to advertise the project at say a convention or a conference, where you could "give away" bitcoins for people to try out the system.... sort of like how the bitcoin faucet currently works but on a larger scale.

[RHorning]

The masses will demand paper, regardless of whether we consider it outdated or foolish.  I think it's a good idea to have a redeemable note and/or check if we want Bitcoin to be available to them.  How it should work I don't know.

I talked about something called "wallet escrow" on this thread awhile back:

https://www.bitcoin.org/smf/index.php?topic=455.0

I think the concept could be applied here in terms of a "throw away" wallet too, where the information would be stored and encrypted in a strong fashion.  My original intent here was to provide a safe way for backing up wallet information so if your computer crashed you could recover the information quickly and it wouldn't even necessarily require anything more than the *very strong* password to recover the information.  I'm thinking a SHA2-512 bit hash or similar kind of high difficulty password, not your run of the mill ordinary passwords here.

In theory you could also "print" your "main" wallet in this fashion too, as a certificate for back-up purposes, and keep that certificate locked in a safe or a bank safety deposit box.  If your local node crashed, all you would need to restore the wallet is to get that hash key.  The hash key would be printed on this certificate in a fashion like serial numbers are used on government-issued currency.

Printing out a certificate where you even print out the quantity of money in that wallet in clear distinguishable letters (40 point bold type or larger) would be basically all that would be needed to get this to work.

[sgtstein]

This is a very interesting idea. The more I read about it, the better it sounds. As RHorning has said, implementing this would give a huge boost to "outside" people and let them know about the project. Using a "wallet escrow" system would make this as secure as normal wallets and prohibit double spending just as we do now. Very nice idea!

The ability to use simple "BitCoin notes" just like everyday paper currency has HUGE advantages for building the system and ease of access for even small business. I would assume that eventually bitcoin will be allowed to use with automated checkout systems IRL like at grocery stores etc. Until then, this definitely gets your foot in the door to those willing to accept it.

Coupling this with an "elevator pitch" would build recognition and acceptance very quickly.

[hugolp]

No.  Imagine if you have a kid mowing your lawn.  In that case I think it would be much easier to hand him a bitcoin certificate for his work than trying to demand that he has bluetooth or a wireless device to receive the payment for services rendered.

  Why wont you use the mobile internet connection or the internet connection of your house? Why does the kid mowing your lawn need to provide a internet connection?

Mind you, this doesn't necessarily have to be done with physical objects.  You could "e-mail" bitcoins in this manner to somebody who doesn't even have a Bitcoin node running, where they could even "redeem" the bitcoins for government-issued money straight away without even getting directly involved with Bitcoins.

This is not very interesting as it drives people away from bitcoins.

As an alternative, the bitcoins could simply be in a thumb drive instead where you could transfer over the files to the merchant representing the bitcoins you wish to use for the purchase, and they could even return the "change" to you in a similar fashion.

This is a good idea, but involves merchant computer use, and it seems similar to me to the smartphone solutions I already mention. The pros of this option is that it seems slightly simpler as the bitcoin program could have a transfer option to a usb wallet (or to a smartphone wallet for the case, they have usb connections). The cons of this option is that you can only access the funds you transfered to the usb dongle (or the smartphone memory).

This seems to me like a smartphone solution, not a paper solution.

All in all, what you are suggesting here is far and away more complex than this paper currency system I'm suggesting here, and has been originally discussed at the start of this thread.  This is a very lightweight bitcoin transfer system that has electronics of any kind as an optional aspect, and can enable purchases even if network access is unavailable on a temporary basis.

I dont think installing a frontend or a wallet for bitcoin in the mobile phone from a app shop is complicated.

What keeps people honest here is that the values can be verified, and double spending is minimized through the verification process.  Somebody who is double spending is committing fraud, which has existing legal implications.  If they obtained those bitcoin certifications from a 3rd party, a legal investigation of fraud would then target that person who created those bogus bitcoin certificates in the first place.

How does the kid that mows the lawn know that the certificate is valid? To really be able to verify the certificate you need a computer, and then the smartphone solution its more practical.


I think that a bitcoin wallet software for mobile phones or usb dongles is more practical, if you dont want to have your phone connected to the internet in any way, than this paper certificates. If this paper would be used without imediate validation in the bitcoin network, they could be unreliable and give bad image to bitcoin currency.

[Insti]

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.

[MoonShadow]

[No.  Imagine if you have a kid mowing your lawn.  In that case I think it would be much easier to hand him a bitcoin certificate for his work than trying to demand that he has bluetooth or a wireless device to receive the payment for services rendered.  

It's not required that the kid have a bluetooth phone, although he is likely to already have one.  It's not even required that *you* have one, although that might make the transfer more convientent.  All that is required is that you have an address of his.  He doesn't need to verify that your money is good; he knows where you live and he couldn't force you to pay him if you refused anyway.  He is dependent upon your honesty from the start, although if you screw him, not only are you going to have to cut your own grass, you might wake up one day and find someone has salted your flowers.

[Insti]

All that is required is that you have an address of his.  

If you mean Bitcoin address, you shouldn't even need this.

He doesn't need to verify that your money is good; he knows where you live and he couldn't force you to pay him if you refused anyway.  He is dependent upon your honesty from the start, although if you screw him, not only are you going to have to cut your own grass, you might wake up one day and find someone has salted your flowers.

Exactly.

[RHorning]

How does the kid that mows the lawn know that the certificate is valid? To really be able to verify the certificate you need a computer, and then the smartphone solution its more practical.


I think that a bitcoin wallet software for mobile phones or usb dongles is more practical, if you dont want to have your phone connected to the internet in any way, than this paper certificates. If this paper would be used without imediate validation in the bitcoin network, they could be unreliable and give bad image to bitcoin currency.

I don't see how this is going to "give bad image to bitcoin currency".  At the moment the concept of bitcoins are completely unknown in any form.

How does a kid know the certificate is valid?  How does that kid know that a check or for that matter government-issued currency is valid?  If that kid takes a check or bank note somewhere and tries to buy something with it (deposit it into a bank or whatever), and the merchant or bank refuses to honor the check or banknote.... the kid knows at that point he has been ripped off and fraud has been committed.  The same kind of test would apply to bitcoin certificates, where those attempting to defraud would get caught red-handed.  It would be the act of using the note which would be the final test, as with all financial instruments.

I'm curious about how you think e-mailing somebody some bitcoins with an e-mail equivalent of a certificate like this would "drive people away from bitcoins"?  If they have a certificate and want to redeem the money, the inclination would be to download a client and join into the network.  Presumably the URL for the Bitcoins client would be on the certificate.  If they purchased government-issued money directly with such a certificate (presumably from one of the exchange websites), they are still using the bitcoins and instead are helping the exchange markets and spreading the coins out to more people.  I fail to see where a down side to the issue of e-mailing certificates would come from.  I'm talking people who would not normally be using Bitcoins, rather than people who are using them and are bailing out of the system.

Mind you, I'm not dismissing the "smartphone" solution either, and I think multiple approaches can and should be tried.  I am talking freedom here, and noting that not all people will fit into a simple worldview of highly connected power computer geeks.  The concept of paper currency is one of many possible solutions, not the one solution that rules all.  I'm also pointing out that the practical issues could be dealt with and make this something that could work.  It does take opening up your mind a little bit and to imagine other possibilities.  Right now the only solution for government money is to use a central bank of some kind or to use paper currency alone.  Almost all arguments against this concept apply equally well to arguments against government-backed paper money as well.  This potential of having a paper currency equivalent for Bitcoins could offer a way to ease a transition for people to get away from government currencies to adopting Bitcoins.

Existing real-world currencies have been established on far and away flimsier grounds and backing than bitcoin certificates, including several "alternative currencies" that are currently accepted by a number of merchants.

[RHorning]

[No.  Imagine if you have a kid mowing your lawn.  In that case I think it would be much easier to hand him a bitcoin certificate for his work than trying to demand that he has bluetooth or a wireless device to receive the payment for services rendered.  

It's not required that the kid have a bluetooth phone, although he is likely to already have one.  It's not even required that *you* have one, although that might make the transfer more convientent.  All that is required is that you have an address of his.  He doesn't need to verify that your money is good; he knows where you live and he couldn't force you to pay him if you refused anyway.  He is dependent upon your honesty from the start, although if you screw him, not only are you going to have to cut your own grass, you might wake up one day and find someone has salted your flowers.

It isn't true that the kid is not in a position to force payment.  If you refused to pay somebody for services rendered, it becomes fraud and can be prosecuted both civilly and criminally as such.  Failure to make payment or paying with an invalid financial instrument are treated exactly the same as if payment never happened.... and indeed worse with a "bad check" because it acknowledges that the debt was legitimate but that the payment was done in an illegal manner with an intent to defraud.  It is that basis that check kiting usually gets people into jail.

Yes, personal integrity does play a role here, but a well structured and functioning judicial system can also play a role to stop would-be con artists from abusing a system of this nature.

I don't know how many kids will take you to small claims court over five dollars (assuming that is a rough price for mowing a lawn), but I'm quite certain that the judge hearing such a case would not be too sympathetic if it got to him in regards to the home owner trying to rip off an young entrepreneur.

[hugolp]

Existing real-world currencies have been established on far and away flimsier grounds and backing than bitcoin certificates, including several "alternative currencies" that are currently accepted by a number of merchants.

As you are guessing, I am not convinced, but maybe you are seeing something I dont. Good luck with the initiative.

[FreeMoney]

 
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.

My understanding is that you don't get any coins from the guy you pay. Your transaction simply involves you sending all of the coin from one of your address; some to the person you are paying and the rest to one of your addresses (change). You don't need to trust his payment.

 
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.

If you are trading with a trusted partner why can't you just pay when you get a machine?

[NewLibertyStandard]

The easiest solution would be to make a user account at MyBitcoin.com, deposit desired amount of bitcoins and then write the user name, password and web address on a piece of paper. You could even suggest he change the email and password or withdraw the funds to complete the transaction.

[MoonShadow]

Another way would be for a bank-like institution to print banknotes with only an address, in both machine and human readable form, onto a difficult to copy banknote.  That way, anyone who was to see it would be able to check the blockchain to make sure that said money is actually associated with that address.  However, the banknotes would have to return to the bank in order for anyone to claim the bitcoins, and the address used would have to be retired.  This allows the pubic to 'audit' the bank at will to make sure that there is full reserve related to the banknotes, and it's difficult for anyone to nab the bitcoins before you deposit them.

Another similar way would be to use the plastic rfid tokens that casinos use, each could have a face value, but report a checkable address when a rfid reader was available.  Once they return to the bank, the rfid tag could be rewritten with a new valid address and sent back out into the flow.

There is no way that I can see that easily copied paper money could work, particularly without a bank.

[RHorning]

The easiest solution would be to make a user account at MyBitcoin.com, deposit desired amount of bitcoins and then write the user name, password and web address on a piece of paper. You could even suggest he change the email and password or withdraw the funds to complete the transaction.

The problem with using a site like "Mybitcoin.com" is that it is a 3rd party website that sort of flies in the face of the decentralized nature of this project.  There are other approaches that don't necessarily require anything other than simply accessing the network as a whole, and not depending on any single website as to if it happens to be up, has their domain name paid for (aka not expired), and doesn't even tempt that the 3rd party maintaining that site to even have the opportunity to watch your transactions in a direct fashion... or involve any sort of direct legal jurisdictional issues that might be associated with that website.

Yes, that would be a quick and dirty way to get this accomplished, and certainly if somebody wanted to go that route, go ahead.  Just don't give up on this idea yet and claim that the issue is solved, as it isn't.

[Anonymous]

The easiest way to carry your cash around  is to have a mobile client you can use on your phone.With the bitcoin app you could just go and stand near someone and your money is transferred.The location of your goods could then be sent to your phone,or you collect the goods when you pay.No one would be aware you did this and to everyone else it would appear no transaction actually took place,just that you took something off the shelf or you stood next to someone looking at your phone....This would also be a great way to use an automatic bitcoin server as you wouldnt have to risk getting your card scammed.Just stand near it and your cash appears on your phone.The only problem with a physical object is you have no deniability.If someone films you handing over a token or cash it makes you look guilty.


(Come to think of it probably a great system for bribing politicians and paying for weed. )

[Anonymous]

Having said that last post,i am in favor of as many ways to access bitcoins as possible.An app on a phone,sms payments,paper certificates,metal tokens,plastic notes,digital iou's,bearer certificates,ripple pay.

[chaord]

Having said that last post,i am in favor of as many ways to access bitcoins as possible.An app on a phone,sms payments,paper certificates,metal tokens,plastic notes,digital iou's,bearer certificates,ripple pay.

I too am in favor of as many processes/mediums/methods as possible.  Incidentally, the guys at http://www.kilowattcards.com/template/index.cfm came up with a pretty cool paper solution.  It actually seems quite similar to bitcoin.  Basically, the paper notes have a serial number on them.  When you give the note to a merchant, or anyone with internet access, they type the serial number in, and get an additional 2 digits.  They cross off the first two digits, and hand write the new digits at the end.  This forms  the new cereal number and prevents double spending.  When the merchant trusts  you he might just skip the verification process or save it for later in the day. Unfortunately this solutions still requires at least some internet capability to prevent fraud.

[MoonShadow]

Having said that last post,i am in favor of as many ways to access bitcoins as possible.An app on a phone,sms payments,paper certificates,metal tokens,plastic notes,digital iou's,bearer certificates,ripple pay.

I too am in favor of as many processes/mediums/methods as possible.  Incidentally, the guys at http://www.kilowattcards.com/template/index.cfm came up with a pretty cool paper solution.  It actually seems quite similar to bitcoin.  Basically, the paper notes have a serial number on them.  When you give the note to a merchant, or anyone with internet access, they type the serial number in, and get an additional 2 digits.  They cross off the first two digits, and hand write the new digits at the end.  This forms  the new cereal number and prevents double spending.  When the merchant trusts  you he might just skip the verification process or save it for later in the day. Unfortunately this solutions still requires at least some internet capability to prevent fraud.

That's pretty cool, and a similar system could be used to create a local paper trade currency backed by bitcoins without the need for expensive printing processes to make it difficult to photocopy.  A note design that incorporates the moving serial number with the 2d machine readable Bitcoin address would work great.  Any computer with a reader could check the blockchain to be certain that the funds actually exist (instant bank audit) while the serial number could be used by literally anyone with the bank's own website to create an anonymous chain of custody of a particular note, so that when the note returned to the bank for redemption and replacement, there is no (likely) way that a counterfit copy (no matter the quality) can be used to claim the funds between the acceptance of the note and depositing it in an account at the bank.  This would allow the Bitcoin backed notes to circulate for a longer period of time with less risk of loss by fraud.

I think that more than a six digit serial would be required, however, and the circulation of the note is limited by the number of blank spaces on the note.

[chaord]

I think that more than a six digit serial would be required, however, and the circulation of the note is limited by the number of blank spaces on the note.

Yeah.  I thought the system was pretty simple and smart too.  I agree though that the serial number would probably need to be longer than 6 digits.  The cool thing is that even if you run out of blank space to write more numbers, you could simply print off another one and start adding more.

[Anonymous]

Nice simple system.A bitcoin version would be redeemable for bitcoins?

[MoonShadow]

Nice simple system.A bitcoin version would be redeemable for bitcoins?

I was thinking that a local version would need some kind of local connection also.  After reading about their kilowatt-hour backed currency idea, that got my mind rolling.  The national currency is so widely accepted, even though it's fiat, because that is all that is accepted by government for payment of taxes.  This is intentional, as it means that there will always be someone in any market with a need for them.  In any city that I know of, the power company is the *one* company that every company and household in the vicinity must deal with.  Even those "greenies" who have a massive phtovoltic array usually deal with the power company on a monthly basis.  So a local currency with dual, concurrent backing would be ideal.  A face value in both bitcoins and kilowatt-hours with an agreement with the local power company.  The bearer could redeem the cash either at the institution that issued them for bitcoins, redeem them at the power company for kilowatt-hours, or just pay someone else with them in the same way that they likely received them.  They could redeem them in an either-or manner, but not both.  The likely result would be that their value would be very close to whichever of those two options was the more valuable at the time.  The issuing institution would need a contract with the power company that fixed the private exchange rate that the institution would be obligaged to repurchase the notes from the power company for, should the power company choose to redeem them for US$, but if the value of the bitcoin face value should exceed the value of a KWH at the residential rate, both the public and the power company itself would likely be redeeming them in bitcoin.  The private exchange rate with the power company does not need to be public, and could likely be set at or near the wholesale power rate.  Which would give the notes themselves an initial arbitrage value that the issuing institution could use to pay for the initial printing, because the creation of cash isn't a free exchange.  The power company would likely require a cap on the total currency in circulation, in order to limit their counter party risk; they simply can't have the entire city paying for all their power at the wholesale rate (from their perspectives).  In my state, the power company is obliged to trade KWH with greenies, but only up to a limit of 1% of the company's total connected load.  I imagine that the cap on currency would be far lower than that.

This would help to keep the currency local as well as keep it in circulation without a need to be tied to the national currency in any explict or fixed way.  Even local governments have to pay for their power, so maybe local taxes would eventually be payable in KWHs/

[Ground Loop]

I'd love to see printed bitcoins.

Basically, a bearer-bond note in a 2D barcode.

The receiver would have no protection against double-spend, so it would behoove them to scan it on-the-spot and get it into the Bitcoin network.  They could wait for a confirmation, or not.

It seems like this would be pretty simple -- get the client to generate a one-time receiving address, pay to it, and then print out the address public/private key pair onto the note.  Any scanner would then have the required keys to receive the transaction and re-spend the coin.

Assuming the receiver has a method to scan & post the note, it's no less secure than any other means of bitcoin payment, right?

[jgarzik]

The receiver would have no protection against double-spend, so it would behoove them to scan it on-the-spot and get it into the Bitcoin network. 

Correct.  And a mobile phone's camera works great as a "scanner."

[MoonShadow]

I'd love to see printed bitcoins.

Basically, a bearer-bond note in a 2D barcode.

The receiver would have no protection against double-spend, so it would behoove them to scan it on-the-spot and get it into the Bitcoin network.  They could wait for a confirmation, or not.

It seems like this would be pretty simple -- get the client to generate a one-time receiving address, pay to it, and then print out the address public/private key pair onto the note.  Any scanner would then have the required keys to receive the transaction and re-spend the coin.

Assuming the receiver has a method to scan & post the note, it's no less secure than any other means of bitcoin payment, right?

Print only the address on the note, so the amount can be verified by any client, but the backing cannot be nabbed by the guy who had the bill last week and render the note useless.  We would want it to circulate more than once.

Personal checks, however, could potentially print the private key, but even that presents a risk that an employee of a company could steal the coins before the company could claim them.

[Insti]

Personal checks, however, could potentially print the private key, but even that presents a risk that an employee of a company could steal the coins before the company could claim them.

Shops seem to do fine accepting dollar bills which are subject to the same risk.

[nelisky]

Personal checks, however, could potentially print the private key, but even that presents a risk that an employee of a company could steal the coins before the company could claim them.

Shops seem to do fine accepting dollar bills which are subject to the same risk.

Yes, but when the dollars get stolen/spent, you no longer hold the bills. It's pretty obvious that something happened.

If you could spend based on the serial of the bill, or something alike, that would be a good analogy.

[MoonShadow]

Personal checks, however, could potentially print the private key, but even that presents a risk that an employee of a company could steal the coins before the company could claim them.

Shops seem to do fine accepting dollar bills which are subject to the same risk.

Um, no, they are not subject to the same risks.  The US FRN is physically the object of value.  With a bitcoin backed note, the paper note is simply data.  If the private key is on the note, that data can be used to take the value of the note without needing to take the note itself.  If we were to make a paper note that had the private keys, it wouldn't be long before some employee was stealing bitcoins from their employer by taking photos of the notes and using the keys to transfer the bitcoins before the company's billing department could do so.  If the private keys were in a machine readable 2d format, how long would it be before some criminal app was developed that could take the photo and transfer the funds automaticly and immediately?  If only the address is present on the note, then anyone could verify that bitcoins exist associated with that address, but could only claim them by bringing it into the institution that issued the note. 

What I cannot resolve is how to prevent the issuing institution from issuing multiple notes with the same address, because the address can be verified, and the rolling serial number checked so that it's not a counterfit copy of another note, but there is no way to verify that said institution isn't engaged in double issuing *itself*.

[Insti]

Um, no, they are not subject to the same risks.  The US FRN is physically the object of value.  With a bitcoin backed note, the paper note is simply data.  If the private key is on the note, that data can be used to take the value of the note without needing to take the note itself.  If we were to make a paper note that had the private keys, it wouldn't be long before some employee was stealing bitcoins from their employer by taking photos of the notes and using the keys to transfer the bitcoins before the company's billing department could do so.

You have an interesting idea of what value is.

It doesn't matter if there is a piece of paper there or not. Either way, the billing department is going to start asking questions and firing (or worse) the guilty parties.

[MoonShadow]

Um, no, they are not subject to the same risks.  The US FRN is physically the object of value.  With a bitcoin backed note, the paper note is simply data.  If the private key is on the note, that data can be used to take the value of the note without needing to take the note itself.  If we were to make a paper note that had the private keys, it wouldn't be long before some employee was stealing bitcoins from their employer by taking photos of the notes and using the keys to transfer the bitcoins before the company's billing department could do so.

You have an interesting idea of what value is.

Do I?  How is that?

It doesn't matter if there is a piece of paper there or not. Either way, the billing department is going to start asking questions and firing (or worse) the guilty parties.

Sure, but it will be too late, and the risks of such a thing happening will prevent businesses from wishing to deal in the paper trade, if not the entire Bitcoin trade.

[Ground Loop]

Maybe I'm dense, but I still don't get it.  The whole point in handling paper bitcoins is to do so without a central "issuing authority".  I want to print my own, and accept them from anyone's home printer.

I totally understand that "showing your bills" to someone gives them a chance to photograph, and "receive them" (steal them, intercept, cash in, whatever).

That's just part of the deal.  You're carrying machine-readable (2d barcode) bearer-coins.  Show them only to the party you are paying, who is expected to transfer them on-the-spot to another account.

The receiver needs a network connection, the payer does not.  Perfect for customer/merchant scenarios.

[FreeMoney]

But it was too late, the employee had already taken 8 days worth of wages....

Printing bitcoins is not all that compelling an idea to me, but it surely isn't because employees will finally have found a way to steal from their employers.

[MoonShadow]

Maybe I'm dense, but I still don't get it.  The whole point in handling paper bitcoins is to do so without a central "issuing authority".  I want to print my own, and accept them from anyone's home printer.

I totally understand that "showing your bills" to someone gives them a chance to photograph, and "receive them" (steal them, intercept, cash in, whatever).

That's just part of the deal.  You're carrying machine-readable (2d barcode) bearer-coins.  Show them only to the party you are paying, who is expected to transfer them on-the-spot to another account.

The receiver needs a network connection, the payer does not.  Perfect for customer/merchant scenarios.

Wht you want are bitcoin checks, then.  That is also doable.

[RHorning]

But it was too late, the employee had already taken 8 days worth of wages....

Printing bitcoins is not all that compelling an idea to me, but it surely isn't because employees will finally have found a way to steal from their employers.

I'm trying to figure out what the complaint is here.  Any employee who handles large amounts of cash is going to have access to that money.  It isn't that hard to play games at the cash register and I'm sure that any kind of fraud that a cashier can do toward their employer applies equally to fiat currency as it does to something like bitcoins.  I would say it is even easier with fiat bank notes... and I've known people who have been convicted of stealing money from their employer because they had access to the cash register.

If you don't trust an employee with cash, don't let them have access to the bank account.  BTW, that is also one of the reasons why the position of comptroller in a company (the person who signs the checks written by the company) is considered one of the key positions and usually ranks just below CEO in terms of importances within the company.  Sometimes CEO and comptroller are the same person, but usually are different to make sure you need permission from both people before money is spent.  Employees stealing from employers is quite common place, which is why finding people for these positions is usually a long process with a whole lot of vetting to make sure they won't rob the company blind.

Certainly any company worth their salt is not going to be putting a minimum wage employee on their first day in front of the cash register unless they are begging to be robbed.

[MoonShadow]

But it was too late, the employee had already taken 8 days worth of wages....

Printing bitcoins is not all that compelling an idea to me, but it surely isn't because employees will finally have found a way to steal from their employers.

I'm trying to figure out what the complaint is here.  Any employee who handles large amounts of cash is going to have access to that money.  It isn't that hard to play games at the cash register and I'm sure that any kind of fraud that a cashier can do toward their employer applies equally to fiat currency as it does to something like bitcoins.  I would say it is even easier with fiat bank notes... and I've known people who have been convicted of stealing money from their employer because they had access to the cash register.

And all the security issues with paper money also applies to paper bitcoin notes and a paper bitcoin note with the private key can also be stolen by remembering that private key in any fashion.  The last thing that we would want to do is add one more security issue with paper bitcoins than already exist with paper money, at least if we actually want businesses to accept them.  Simply put, the private key cannot be on the paper notes, period.  There is no way to make that workable.

[Ground Loop]

You seem pretty certain about it, creighto.
I'm not trying to change your mind, and if I and a merchant can find a system that works for "handing over" physical Bitcoins, I suppose it doesn't have to involve anyone else.

As a thought experiment, imagine the "scratch off" lottery tickets.  You can't see the receiving key until you scratch it, which makes it visibly void.  A drawer full of these ought to alert the shift manager than an employee isn't following SOP. 

I don't really get the difference betwen "checks" and printed coins, except that a check sounds like it involves an intermediate processor -- a cashing authority or bank.  No can do.  The whole point is anonymous payer, anonymous receiver.  I don't want to know who cashed the check, and I don't want them knowing who wrote it.

If I'm willing to divulge everything, might as well have a Bank Of Bitcoin MasterCard and leave it at that.

[MoonShadow]

You seem pretty certain about it, creighto.
I'm not trying to change your mind, and if I and a merchant can find a system that works for "handing over" physical Bitcoins, I suppose it doesn't have to involve anyone else.

True, and that is pretty much what your personal checking account is supposed to be, even though it isn't.  There is no hidding one's identity in a two party (or three party) arrangement, however.

As a thought experiment, imagine the "scratch off" lottery tickets.  You can't see the receiving key until you scratch it, which makes it visibly void.  A drawer full of these ought to alert the shift manager than an employee isn't following SOP. 

Now that's an idea, but it would still become void for the purpose of futher trade should anyone, honestly or not, scratch off the hidden zone to get to the private key.  But so long as each person continued to trust that the bitcoins behind the visable address, something checkable, there might not be any reason to scratch off the hidden portion of the note in order to claim the bitcoins themselves.  Eventually, however, someone will do so in order to buy something online, so the "lifespan" of such a note is still limited.  But it would certainly be as anonymous as cash, and never require that any person along the chain of trade walk into any kind of bank to redeem them.

Something to consider.  I wonder how much it costs to print something like that.

I don't really get the difference betwen "checks" and printed coins, except that a check sounds like it involves an intermediate processor -- a cashing authority or bank.  No can do.  The whole point is anonymous payer, anonymous receiver.  I don't want to know who cashed the check, and I don't want them knowing who wrote it.

Well, a bitcheck would have to be processed after only one trade, just like a normal check, but not neccessarily by an institution.  The receiver could, and probably should, process one on his own client immediately; because without the mutual trust of a third party (a bank) the receiver cannot be assured of the payer's honesty without doing so while he is still present.  Of course, as you said, if you have immediate access to a running client, what good would a check serve?

If I'm willing to divulge everything, might as well have a Bank Of Bitcoin MasterCard and leave it at that.

I've got bad news for you, there is a place for banking institutions within the future Bitcoin economy, and there almost certainly will be such banks.

[btchris]

As a thought experiment, imagine the "scratch off" lottery tickets.  You can't see the receiving key until you scratch it, which makes it visibly void.  A drawer full of these ought to alert the shift manager than an employee isn't following SOP. 

Now that's an idea, but it would still become void for the purpose of futher trade should anyone, honestly or not, scratch off the hidden zone to get to the private key.  But so long as each person continued to trust that the bitcoins behind the visable address, something checkable, there might not be any reason to scratch off the hidden portion of the note in order to claim the bitcoins themselves.  Eventually, however, someone will do so in order to buy something online, so the "lifespan" of such a note is still limited.  But it would certainly be as anonymous as cash, and never require that any person along the chain of trade walk into any kind of bank to redeem them.

Something to consider.  I wonder how much it costs to print something like that.

I really like this idea. It turns out you can buy clear stickers with scratch-off material applied to the top fairly cheaply. A quick search turned up these, which are 1.5 x 2 inches, and cost between 5 and 8 cents each, depending on qty: http://www.easyscratchoffs.com/rectangle-scratch-off-stickers.html

I wonder how big an area would be needed to print a private key in a 2d barcode of some sort?

[nelisky]

Scratch-offs are an amazing idea. They could have qrcode to a mybitcoin address, and the password be used as 'PIN code' like in an ATM machine, thus loosing the card would not mean loosing the coins.

Also, you could pair a bunch of same address cards that you hand off to (physical) merchants, and have another scratch off with 10 BTC worth codes, each one single usage. you could easily see if someone used your codes as they would be scratched off. So you hand out one qrcoded scratch off, and you use your own multi pin card and scratch as many as as 10BTCs you need. If they where those 'easy rip apart' things you could actually hand over the codes too

You would then carry only as many pin codes as you wanted to carry around, reducing the possibility of loosing them. But if you did loose them, you could completely cancel all unused address/pin code pairs.

[Insti]

Scratch-offs are an amazing idea.

Or you could just fold it over and staple it.

[MoonShadow]

Scratch-offs are an amazing idea.

Or you could just fold it over and staple it.

The receiver could never be certain that the private key hasn't already been copied by other means.  Same with an evelope, before anyone mentions it, because the receiver cannot be certain that the evelope is the original. 

It's a great deal more tricky to put the grey coating back over a scratch-off, which is exactly the reason that the lottery commisions use them.

[nelisky]

Scratch-offs are an amazing idea.

Or you could just fold it over and staple it.

The receiver could never be certain that the private key hasn't already been copied by other means.  Same with an evelope, before anyone mentions it, because the receiver cannot be certain that the evelope is the original. 

It's a great deal more tricky to put the grey coating back over a scratch-off, which is exactly the reason that the lottery commisions use them.

Although with this sticker style coating thingies, it gets much easier

But I was only considering an online transaction, as in debit card style. For offline usage, I'm not sure I have read of thought about a single system that would work, without some central issuer and physical material that is hard to counterfeit and/or more expensive to copy than the actual value it holds.

[MoonShadow]

[But I was only considering an online transaction, as in debit card style. .

Uh, Why?

This entire thread has been about using bitcoins in person and IRL.  You can already use bitcoins online, that's the point.

[RHorning]

Scratch-offs are an amazing idea.

Or you could just fold it over and staple it.

The receiver could never be certain that the private key hasn't already been copied by other means.  Same with an evelope, before anyone mentions it, because the receiver cannot be certain that the evelope is the original. 

It's a great deal more tricky to put the grey coating back over a scratch-off, which is exactly the reason that the lottery commisions use them.

It still is technically possible to find out what is underneath the grey paint with the scratch-off paint/ink used to cover over the numbers/barcode.  The question would be if the cost to do so would be more (aka using an x-ray machine to take a photograph or some other similar system) would be worth the effort to find out.

I presume another "home printing" option would be to use a silk screen with the ink in question to cover over the code used to transfer the coins electronically.  A simple home screen can be made for roughly $50-$100 (with print-quality screen material) and the ink itself can be purchased for relatively minimal cost.  A link for the ink can be found here:  http://www.iicink.com/si_scratchoffsolvent.html  Another link that discusses some of the technical problems for doing this can be found here:  http://printplanet.com/forums/ink-substrates-consumables-discussion/15180-scratch-off-inks

The costs involved with making these bills, even with the scratch off area, is largely dependent upon what kind of volume and how much effort you as an individual want to put into them.

[nelisky]

[But I was only considering an online transaction, as in debit card style. .

Uh, Why?

This entire thread has been about using bitcoins in person and IRL.  You can already use bitcoins online, that's the point.

Well, it might just be me, but walking into the (insert favorite large surface store here), standing in line for 10 minutes and, already having 10 other people behind me I head to the counter and they say: "that will be 5461BTCs please, sir" to which I reply:

- Wait, I'll just log in in my android phone, how was that 64 random characters address again? 'T' or 'D' again? Can you write that down, thank you.
- It will just be 10 minutes now, sir...

Ok, maybe it doesn't have to be this way, but this check / note/ scratch ticket thingy will still need to be confirmed online, or else there's really little you can do to avoid fraud, and that will do more hurt to bitcoins that one initially imagines. Sure, completely offline secure transactions would rock, but I just thought this would be a great middle ground solution. Easy to create, hard to copy without physically stealing, easy to assert if used before. I personally think it would rock

And it would make it much easier to sell this idea to local shops, while also allowing offline transactions between parties with some trust level, as in the 'neighbor kid moans the lawn' scenario.

[Ground Loop]

as in the 'neighbor kid moans the lawn' scenario

Your neighborhood sounds pretty fun. 

Is it possible that 'testing' a bitcoin bill for double-spend could be done much faster than confirmation?

After all, you just want to know if the coin has been previously spent.

SO the cashier takes the bill with the 2D barcode, scans it, and the register confirms that the coin hasn't been previously spent (ie, the balance is real).  The confirmations can come later if the merchant wants to extend some trust.  Seems this wouldn't take any longer than a Visa authorization.

In a nutshell, my goal is to pay for something
1) Anonymously (thank you sir, you have no idea who I am.)
2) Spontaneously (I wasn't planning to spend bills at lunch, but here I am)
3) Off-line (I didn't bring my gadgets)
4) Minimal trust required (Give me physical goods, and you have reasonable confidence my bill is good.)

A completely separate discussion would be valid for discussing a quick way to share BTC addresses, IRL.  Cut & Paste works fine.  "Read your number to me" would not.  A standard 2D sticker on the back of a register would be the ticket here.  "BTC Accepted @" with a phone client that scans and pays.

[MoonShadow]

as in the 'neighbor kid moans the lawn' scenario

Your neighborhood sounds pretty fun. 

Is it possible that 'testing' a bitcoin bill for double-spend could be done much faster than confirmation?

Certainly, if the receiver is willing to trust that his own client is up to date.

At least as well as the credit card companies can promise that the person who is holding the card didn't steal it.

After all, you just want to know if the coin has been previously spent.

SO the cashier takes the bill with the 2D barcode, scans it, and the register confirms that the coin hasn't been previously spent (ie, the balance is real).  The confirmations can come later if the merchant wants to extend some trust.  Seems this wouldn't take any longer than a Visa authorization.

Quicker, actually; since the Point-of-sale system within the store could check that address against it's own client in milliseconds.  Credit cards are usually assumed to be good for orders under $50 anyway.

In a nutshell, my goal is to pay for something
1) Anonymously (thank you sir, you have no idea who I am.)
2) Spontaneously (I wasn't planning to spend bills at lunch, but here I am)
3) Off-line (I didn't bring my gadgets)
4) Minimal trust required (Give me physical goods, and you have reasonable confidence my bill is good.)

A completely separate discussion would be valid for discussing a quick way to share BTC addresses, IRL.  Cut & Paste works fine.  "Read your number to me" would not.  A standard 2D sticker on the back of a register would be the ticket here.  "BTC Accepted @" with a phone client that scans and pays.

Bluetooth in the register.

[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

[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?

[em3rgentOrdr]

What about Printable RFID Tags with printable transistors that can store, read, and write data:

http://www.popsci.com/technology/article/2010-03/cheap-plastic-rfid-tags-promise-replace-bar-codes

cheap...currently 3 cents each, possibly as low as 1 cent each:


and flexible too


Or instead just use good old RIFD tags with really cheap embedded memory chips inside of a hard plastic, cardboard, or even paper?

[LZ]

In the event of war with the use of EMP generators I would prefer non-electronic storage method.

[em3rgentOrdr]

In the event of war with the use of EMP generators I would prefer non-electronic storage method.

Of course yes, you might want to print a physical copy of your wallet to paper for long term storage, but i think the main topic of this thread is for printing bitcoin notes for day-to-day person-to-person exchanges without having to carry around your gaget or be connected to the network, NOT necessarily long-term storage.  People currently don't carry around cash for long term storage...they just keep enough money in their pocket to handle day-to-day person-to-person transactions...they don't keep their whole life savings as cash inside their wallet.

[em3rgentOrdr]

I was just brainstorming now thinking outside the box: maybe instead of thinking that we have to keep all the code inside one piece of paper, maybe we should be thinking about a printed coding scheme that uses one or more of the following operations:

• split the printed code in half when making a transaction
• modify the printed code when making a transaction
• append more code to the printed code when making a transaction
• destroy and recreate the printed code when making a transaction
• having two pieces of paper with different printed codes for each note

Of course I didn't give any solutions here...just some brainstorming in case this sparks some other ideas the clever people out there on the bitcoin forum...

Also, what about the idea of using self-destroying codes somehow to prevent double spending.  Maybe volatile RFID memory that when scanned gets erased.  Or maybe some special ink that changes its chemical properties when exposed to certain light, causing the code to get erased when scanned.  Or maybe some online database that self-destructs when the url is accessed (such as my 10BTC wallet file I stored on-line as a self-destructing message whose url I encoded in a QRcode...that 10BTC wallet is still up for grabs ).  Or maybe using some expiration date scheme for each note...if we have short-life span notes then that means it is less likely for those double spending in its lifetime.  For instance, I just stumbled upon Vansih - Self Destructing Digital Data which will use on line Distrusted Hash Tables to store an encrypted message and key which will decay in a specified amount of time, say 8 hours.

[theymos]

You could print out the public/private keys, but send your coins to that key with a special transaction that also requires a password to claim (done securely with the hash functions and a salt). Then tell the recipient the password orally. An attacker needs to both hear the password component and scan the key component.

You wouldn't want to use just a password because your transaction would then be vulnerable to MITM attacks.

[MoonShadow]

You could print out the public/private keys, but send your coins to that key with a special transaction that also requires a password to claim (done securely with the hash functions and a salt). Then tell the recipient the password orally. An attacker needs to both hear the password component and scan the key component.

You wouldn't want to use just a password because your transaction would then be vulnerable to MITM attacks.

Might work for major transactions, but can you see yourself doing this in the checkout line at Kroger?

[theymos]

Might work for major transactions, but can you see yourself doing this in the checkout line at Kroger?

People already use PIN entry screens for debit cards, which is pretty much the same.

[leryn17]

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

I haven't tried printing coins. But I think, printing bitcoins will probably work. It is possible to identify it as the user-created paper money.

[anarchy]

Why print something when digital is the way to go?

[Anonymous]

Why print something when digital is the way to go?

I have a book sitting on my bookshelf that is 200 years old. Do you think you will still be able to read your chosen digital format in 200 years?

[jgarzik]

I have a book sitting on my bookshelf that is 200 years old. Do you think you will still be able to read your chosen digital format in 200 years?

Indeed.

Furthermore, all known digital media -- magnetic tape, magneto-optical, CD, DVD, hard drive, flash drive -- deteriorates over time.  While many of us old codgers have 20-year-old hard drives that still work, your "average" media can start losing data in under 10 years.

Machine-readable, printed material is far more durable than that.

[Bitquux]

Why print something when digital is the way to go?

I have a book sitting on my bookshelf that is 200 years old. Do you think you will still be able to read your chosen digital format in 200 years?

Do you have any 200-year-old bank notes? If you do, would they still be honored? I can't even keep current bills in my wallet for long. If you want long term storage, convert to something you feel is likely to retain value (nothing is guaranteed). This is currency, not artifacts or knowledge. It's supposed to be used.

In the case of some war involving EMP, many smaller electronics should survive. Even so, if you're worried about that, you should stock up on things like food, medical supplies, and beer. That's what what people will want when the lights go out.

[MoonShadow]

In the case of some war involving EMP, many smaller electronics should survive. Even so, if you're worried about that, you should stock up on things like food, medical supplies, and beer. That's what what people will want when the lights go out.

You should be doing that anyway, if you have the funds to risk in investments, you should be trying to limit your risks of personal loss in the unlikely event of a social crisis before placing any funds at risk for a retirement.  Even the bible talks about this in many places.  It's so central to the Mormans' religious interpretation that households are obligated to stock up for a year for their entire family, so as not to be a burden upon the community in the event of social collapse.  Morman churches usually have a collective food pantry controlled by the head of the local church (bishop?) to cover this obligation concerning the missionaries (mostly young men in college) who are no longer a part of their parents' household and not yet at the point in life to establish their own household.

Mormans take the passage, "A fool spends all that he has, but the storehouses of the wise are filled with choice food and oil" very seriously.  Considering that they are the only denomination to have experienced a real war with the US Government at any point in history, they might have something to contribute to plans for a future that that same government goes mad.

[em3rgentOrdr]

As has been mentioned by many bitcoiners several times in this thread, why bother printing bitcoins, when the future of payment will be on your cell phone?  From http://www.pcworld.com/article/210735/android_23_will_do_mobile_payments_and_lots_of_bump.html:

Android will soon support mobile payments (starting with Android 2.3), and some future Android phones--the Nexus S might be the first--will contain NFC (near field communication) chips. NFC chips can effectively turn your smartphone into a credit card of sorts by broadcasting data to other NFC-speaking machines. For example, you would be able to walk into a store, "bump" your phone on a NFC sensor there, and pay for your goods without having to pull out a credit card or cash. Some retailers may start accepting smartphone payments as early as next year.

So it seems that it may not necessarily be terribly important to have to print bitcoins anyway.  Maybe someone can write a cellphone app to handle bitcoin payments via bumping?

Any thoughts?

[Anonymous]

Why print something when digital is the way to go?

I have a book sitting on my bookshelf that is 200 years old. Do you think you will still be able to read your chosen digital format in 200 years?

Do you have any 200-year-old bank notes? If you do, would they still be honored? I can't even keep current bills in my wallet for long. If you want long term storage, convert to something you feel is likely to retain value (nothing is guaranteed). This is currency, not artifacts or knowledge. It's supposed to be used.

In the case of some war involving EMP, many smaller electronics should survive. Even so, if you're worried about that, you should stock up on things like food, medical supplies, and beer. That's what what people will want when the lights go out.

We use plastic notes here. 

[Bitquux]

We use plastic notes here. 

They'll be cabon nanofiber notes in 200 years. Or bitcoins. Either way your plastic will be worthless. What were we talking about?

[MoonShadow]

We use plastic notes here. 

They'll be cabon nanofiber notes in 200 years. Or bitcoins. Either way your plastic will be worthless. What were we talking about?

I prefer Post-it for my notes.