I just made my first Bitcoin ATM withdrawal... 3BTC from my printer.

[casascius]

Being my own bank.  The first three real notes.  Funded and ready to spend.

I have been modifying my Casascius Bitcoin Utility to accept a .png file in the same directory as the .exe, and use it as background artwork for the paper wallet generator feature.

[1714970588]

1714970588

[smoothie]

very nice! Can I have them?

[casascius]

very nice! Can I have them?

I'm hoping yes... I'm planning on releasing the source code I used to print these.

[mdosi]

Very nice work

[rockxie]

Interested in the content under your finger . 

[ymgve]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

[rebuilder]

Excellent. Not a week ago, it occurred to me merchants aren't the ones who should have QR codes printed - people looking to spend BTC in the real world should print out small-denomination bills, and merchants just need a QR reader.

How is change handled? If I want to use such a bill to pay for something less than the sum held by the private key, is there a way for the merchant to easily return the change to another address I own, not linked to the private key printed on the bill?

[hxtop]

nice work
good idears.

[D.H.]

For those who missed it, this is the original thread where the banknote was designed.

[D.H.]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

[556j]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So to scan it you'd need a mobile phone, what's the benefit of having paper at all then? I'm trying to think of uses for this and it seems there's very limited and specific scenarios it'd be useful.

[unclemantis]

+1

[BoardGameCoin]

Plz  to be giving us the codez?

[kwukduck]

very nice, would be cool if everybody could do that easily themselves.

[casascius]

One word - whatifsomeone(athirdparty)hadatelephotolenseasyouexchangednotes?

Then I'd be effed to the tune of 3 BTC.

Print 'em in small denominations.

It's worth pointing out that when you print these notes and hold them in the flesh, the QR codes are giant and far bigger than they need to be to be readable.  They would scan reliably at 1/9 the size.

[bg002h]

Brilliant!

[Gyrsur]

soo fantastic!! imagine you can spend this as a gift... amount of bitcoins should als appear on the BTC banknote... very exciting!! great work!! bitcoin up up up...

[ErebusBat]

soo fantastic!! imagine you can spend this as a gift...

This is my idea too... give them as gifts / talking points.

I am a nasty bastard though and I am thinking of putting a VALID UNTIL_______ field so if they don't get off their lazy dufs for 3 months after I give them I can get my BTC back!

[Gyrsur]

Excellent. Not a week ago, it occurred to me merchants aren't the ones who should have QR codes printed - people looking to spend BTC in the real world should print out small-denomination bills, and merchants just need a QR reader.

How is change handled? If I want to use such a bill to pay for something less than the sum held by the private key, is there a way for the merchant to easily return the change to another address I own, not linked to the private key printed on the bill?

yes it's very simple! you have to have BTC banknotes down to 1 Satoshi and give these banknotes back as the change... 

[Gyrsur]

soo fantastic!! imagine you can spend this as a gift...

This is my idea too... give them as gifts / talking points.

I am a nasty bastard though and I am thinking of putting a VALID UNTIL_______ field so if they don't get off their lazy dufs for 3 months after I give them I can get my BTC back!

then you have to copy the private key for yourself and should manage the expire date also yourselve to move the amount after this date away...

...but wait a minute! the private key on the banknote should be sealed somehow!!

and the paper has to be banknote paper, please! because of the feeling... Casascius are you able to manage this?

[casascius]

Excellent. Not a week ago, it occurred to me merchants aren't the ones who should have QR codes printed - people looking to spend BTC in the real world should print out small-denomination bills, and merchants just need a QR reader.

How is change handled? If I want to use such a bill to pay for something less than the sum held by the private key, is there a way for the merchant to easily return the change to another address I own, not linked to the private key printed on the bill?

yes it's very simple! you have to have BTC banknotes down to 1 Satoshi and give these banknotes back as the change...  

I expect any POS system that read QR codes would offer to read another QR code (bitcoin address only) to determine where the change goes.  Practical options for returning change include:

1. If the merchant has a POS-style printer, they could simply issue your change as a new QR code on receipt paper.

2. You could carry around a little keyfob on your key chain (similar to what BitPay now offers) which returns your change back to somewhere like your computer at home.  That way you don't have to worry about valuable scraps of paper that might fade on you, and you always have an easy way to receive funds anytime.

3. Change could always be sent back to one of the bills you presented for payment, or to another bill you're already carrying.

[DrFred]

1 and 3 can't work, as 1 would leave control of the private key with the vendor. 3 defeats the purpose of having a denomination on the note.

[ErebusBat]

This has been hashed and rehashed in the original thread.

The point of these are not to do the 'suitcase full of cash' transactions.  Just a few here and there, most likely in mircopayments with the price the way it is now.

[casascius]

1 and 3 can't work, as 1 would leave control of the private key with the vendor. 3 defeats the purpose of having a denomination on the note.

1 is likely to work more for social reasons, not technical reasons.  Sure, the vendor could swipe you for 0.23 BTC, if they want to leave a bad taste in your mouth.  They could also double-charge your VISA today, but by and large they don't.  Now, you do want to watch out for dishonest clerks, because they might have less of a stake and would be more interested in scamming you.  But the same way people know to do due diligence now to protect themselves from hacks of online wallets, so can people learn to avoid getting scammed by clerks (e.g. don't let the clerk snap photos of your change paper, or use method #2 or #3 whenever possible).

3, given the notes are meant to be disposable, simply crossing out the denomination and writing a new one isn't all that outrageous.  Or putting a small tear in the note to signal it has been partially spent.  Not all notes have to be printed pre-denominated.  Notice on my sample notes I simply hand-wrote 1 BTC on them and I don't consider this a terrible flaw.

[nolo200]

1 and 3 can't work, as 1 would leave control of the private key with the vendor. 3 defeats the purpose of having a denomination on the note.

1 is likely to work more for social reasons, not technical reasons.  Sure, the vendor could swipe you for 0.23 BTC, if they want to leave a bad taste in your mouth.  They could also double-charge your VISA today, but by and large they don't.  Now, you do want to watch out for dishonest clerks, because they might have less of a stake and would be more interested in scamming you.  But the same way people know to do due diligence now to protect themselves from hacks of online wallets, so can people learn to avoid getting scammed by clerks (e.g. don't let the clerk snap photos of your change paper, or use method #2 or #3 whenever possible).

3, given the notes are meant to be disposable, simply crossing out the denomination and writing a new one isn't all that outrageous.  Or putting a small tear in the note to signal it has been partially spent.  Not all notes have to be printed pre-denominated.  Notice on my sample notes I simply hand-wrote 1 BTC on them and I don't consider this a terrible flaw.

I personally LOVE this idea casascius!  I want to see BTC accepted in more physical stores/restaurants and I think this is the way to do it.  I like #1.  If you are concerned about the private key, just take your receipt to your table/car and scan it with your phone and move to your own address.

[niko]

These are skimmed much more easily than credit or debit cards - all you need is a camera, not even physical access. There is also the issue of change. Wasted paper, too. Any smartphone can display QR codes on demand, only when needed. Perhaps a nice chimera would be an e-paper note. Sounds too much like the "Bitcoin Card"? It does, but I think Casascius is more than qualified to look into similar solutions and to innovate.

[casascius]

These are skimmed much more easily than credit or debit cards - all you need is a camera, not even physical access. There is also the issue of change. Wasted paper, too. Any smartphone can display QR codes on demand, only when needed. Perhaps a nice chimera would be an e-paper note. Sounds too much like the "Bitcoin Card"? It does, but I think Casascius is more than qualified to look into similar solutions and to innovate.

They are meant to be disposable.  You would not "loan" these to somebody the same way you would loan a Federal Reserve note.  You would print them for your own use and keep them in your own physical wallet until you're ready to spend them.

Any smartphone can display QR codes on demand, but that demand takes 30-60 seconds to issue, assuming you have good wireless signal, and makes you unpopular if you're at the head of the lunch line and there's two dozen people behind you.  With the cash, you can hand it over, and *beep* be done, and your change goes back to your bill, or your BitPay keyfob, or is handed to you on receipt paper.  It's even faster than VISA.  (Assuming the merchant has the appropriate POS system... but believe me, this is coming!)

[SgtSpike]

These are skimmed much more easily than credit or debit cards - all you need is a camera, not even physical access. There is also the issue of change. Wasted paper, too. Any smartphone can display QR codes on demand, only when needed. Perhaps a nice chimera would be an e-paper note. Sounds too much like the "Bitcoin Card"? It does, but I think Casascius is more than qualified to look into similar solutions and to innovate.

If you have a smartphone, why go through the trouble of displaying a private key to begin with, instead of simply creating a Bitcoin transaction yourself and sending the funds to the vendor's address?

I like the paper throwaway bills (and these aren't the first ones we've seen).  They would work well for the purpose they are made for.  I think it was mentioned before in a different thread that the likelihood of a scammer being able to create a transaction to skim the funds even just 10 seconds after the vendor created their transaction would be less than 1%, assuming the scammer didn't hold a significant amount of hashing power.  Remember that the standard client will reject second transactions if a first has already been broadcast claiming the funds.  And if the scammer DID hold a significant amount of hashing power, what would they be doing with trying to scam 1 BTC here and there in in-person transactions?

[niko]

I'm starting to warm up to this. I apologize if kicking at an open door, but private key can in principle be encrypted, and POS infrastructure could be decrypting it, right? The system could be assymetric and involve public key and denomination as seed/salt...? (Haven't thought this through at all)

[mobile4ever]

That's awesome! Good for you. Does it work with android, blackberry, iPhone and the rest?

[casascius]

I'm starting to warm up to this. I apologize if kicking at an open door, but private key can in principle be encrypted, and POS infrastructure could be decrypting it, right? The system could be assymetric and involve public key and denomination as seed/salt...? (Haven't thought this through at all)

It could be, but for this purpose it's not encrypted at all.

I actually did make a proposal on the Wiki as to a key/QR code format that is protected with a password.  That could be done - in which case you'd hand over the cash and say "the password to my cash is foofoo".

I am not sure it would be very practical, because the purpose of printing the cash is to save transaction time, and if the password is long, you waste any time you saved as the cashier types it, and if the password is short, someone who skims the code could crack it, rendering the protection useless.  The most practical remedy may be low-tech: cover the spend code with a small post-it note.

Password-protected cash also increases the training burden on staff who would be employed to accept it, which makes the deal a little more raw for merchants.  The more the bills can function like retail gift cards from the perspective of the clerk, the less often you'll run into clerks who have no clue how to accept them.

[Dansker]

Definetely the kind of thing you need if you go drinking or to a casino paying with bitcoins.

This way you can bring the amount of money you are willing to risk/spend, and not worry about everything else.

[Gyrsur]

I love the idea of BTC banknotes since I saw the photo from Casascius! but I think we have to make a difference between two worlds. the geek world and the ordinary world. bitcoin until now is a currency for geeks. with this BTC banknotes it can become a currency for ordinary people too. let thinking about cryptography at the geeks and give the rest BTC banknotes... in detail it could be mean this: the private key should be inside of the BTC banknote so if you want to use the amount in the common old way you have to destroy the BTC banknote and then you can use the value as before. but until this you have to use BTC in a common way of a currency.

BTW the paper should be a high quality paper like a foil or something like this...

BTC banknotes should be available down to 1 bitcent at the moment it means you can divide a dollar down to 10 cents

the other question is: is Bitcoin ready for the second storm? if this idea will light up Bitcoin will get much more attention as one year ago... from governments, hackers, all the rest...

only my humble opinion, my intention is to put Bitcoin forward in the way of coming to solutions via swarm intelligence

 

[casascius]

the private key should be inside of the BTC banknote so if you want to use the amount in the common old way you have to destroy the BTC banknote and then you can use the value as before. but until this you have to use BTC in a common way of a currency.

That's exactly how Casascius Coins work, but then you have to pay extra for the coins plus shipping and wait for them to arrive, which is a disincentive to spending them like cash.  Most people buying Casascius Coins are collecting them or using them to promote Bitcoin.

Printing your own bills eliminates the premium cost, the shipping cost, and the shipping wait, at the expense of not having the code covered up.  For applications where a covered code isn't necessary, it hits a sweet spot.

Printing the bills and cutting them out takes time and costs money in supplies, but is not bad if you compare it to the time it takes to drive to an ATM and the cost of an ATM fee.

BTW the paper should be a high quality paper like a foil or something like this...

Since the goal is to release the program to the world for free, open-source, you'll be able to print on anything you can shove into the printer.

BTC banknotes should be available down to 1 bitcent at the moment it means you can divide a dollar down to 10 cents

Likewise when you're printing them yourself - you can have one for 23 bitcents if you want.

[Gyrsur]

BTC banknotes should be available down to 1 bitcent at the moment it means you can divide a dollar down to 10 cents

Likewise when you're printing them yourself - you can have one for 23 bitcents if you want.

yeah, if i want to pay my beer in a pub with bitcoins then i have to take a 1BTC banknote with me and will get back a 50 bitcent and a 20 bitcent banknote. the rest is tip...

[giszmo]

If you are concerned about the private key, just take your receipt to your table/car and scan it with your phone and move to your own address.

So the waiter has plausible deniability if he is faster than you. Anybody in the room could have taken a picture of the receipt while falling out of the printer, spied on the electromagnetic waves the printer produced etc.

(Yes I'm one of those skeptics who think it is a bad idea to print private keys in the first place. Bitcoin are digital money. Printing them is a nice gadget but of no practical relevance in any future I can imagine.)

[Gyrsur]

If you are concerned about the private key, just take your receipt to your table/car and scan it with your phone and move to your own address.

So the waiter has plausible deniability if he is faster than you. Anybody in the room could have taken a picture of the receipt while falling out of the printer, spied on the electromagnetic waves the printer produced etc.

(Yes I'm one of those skeptics who think it is a bad idea to print private keys in the first place. Bitcoin are digital money. Printing them is a nice gadget but of no practical relevance in any future I can imagine.)

i disagree, if you want to have a critical mass using bitcoin you should try to think as the critical mass. humans want to have something in there hands and something what is easy to use. if i got 4 beers in a pub maybe i'm not able to use my mobile anymore...

[unclemantis]

I'm starting to warm up to this. I apologize if kicking at an open door, but private key can in principle be encrypted, and POS infrastructure could be decrypting it, right? The system could be assymetric and involve public key and denomination as seed/salt...? (Haven't thought this through at all)

It could be, but for this purpose it's not encrypted at all.

I actually did make a proposal on the Wiki as to a key/QR code format that is protected with a password.  That could be done - in which case you'd hand over the cash and say "the password to my cash is foofoo".

I am not sure it would be very practical, because the purpose of printing the cash is to save transaction time, and if the password is long, you waste any time you saved as the cashier types it, and if the password is short, someone who skims the code could crack it, rendering the protection useless.  The most practical remedy may be low-tech: cover the spend code with a small post-it note.

Password-protected cash also increases the training burden on staff who would be employed to accept it, which makes the deal a little more raw for merchants.  The more the bills can function like retail gift cards from the perspective of the clerk, the less often you'll run into clerks who have no clue how to accept them.

+1

[Kupsi]

BTC banknotes should be available down to 1 bitcent at the moment it means you can divide a dollar down to 10 cents

Likewise when you're printing them yourself - you can have one for 23 bitcents if you want.

yeah, if i want to pay my beer in a pub with bitcoins then i have to take a 1BTC banknote with me and will get back a 50 bitcent and a 20 bitcent banknote. the rest is tip...

If you go to your regular pub, you would take many 30 bitcent banknotes with you

[casascius]

So the waiter has plausible deniability if he is faster than you. Anybody in the room could have taken a picture of the receipt while falling out of the printer, spied on the electromagnetic waves the printer produced etc.

(Yes I'm one of those skeptics who think it is a bad idea to print private keys in the first place. Bitcoin are digital money. Printing them is a nice gadget but of no practical relevance in any future I can imagine.)

In a BTC-welcoming restaurant scenario, you are far more likely to receive your change as multiple BTC bills pre-printed by the restaurant in a small denomination conducive to leaving tips, with scratchoffs protecting the private key.  Your restaurant receipt will list the firstbits of the change bills that were activated for you as proof that the bills were funded by the waiter before being brought to you.

[Serith]

In a BTC-welcoming restaurant scenario, you are far more likely to receive your change as multiple BTC bills pre-printed by the restaurant in a small denomination conducive to leaving tips, with scratchoffs protecting the private key.  Your restaurant receipt will list the firstbits of the change bills that were activated for you as proof that the bills were funded by the waiter before being brought to you.

Or they can make new private key for the change and print it on the receipt.

[casascius]

In a BTC-welcoming restaurant scenario, you are far more likely to receive your change as multiple BTC bills pre-printed by the restaurant in a small denomination conducive to leaving tips, with scratchoffs protecting the private key.  Your restaurant receipt will list the firstbits of the change bills that were activated for you as proof that the bills were funded by the waiter before being brought to you.

Or they can make new private key for the change and print it on the receipt.

Then the waiter can steal it with a camera phone - that is the concern I was looking to address.

[SgtSpike]

In a BTC-welcoming restaurant scenario, you are far more likely to receive your change as multiple BTC bills pre-printed by the restaurant in a small denomination conducive to leaving tips, with scratchoffs protecting the private key.  Your restaurant receipt will list the firstbits of the change bills that were activated for you as proof that the bills were funded by the waiter before being brought to you.

Or they can make new private key for the change and print it on the receipt.

Or they can just send the change back to an address of your choosing - no need for physical bills at all.  If you WANT that address to be a physical bill, however, you could certainly just provide the address for them to send it to.

There is no reason for a restaurant, pub, or any other modern establishment of the sort should be handing back physical Bitcoin change.

[Gyrsur]

i fear you guys got not the point i tried to explain: there exists btc as online money and there could exist btc as offline money like cash. the last thing has to be managed somehow with the first thing in mind.

the third thing is the network which is the foundation of bitcoin. this it where the value comes from...

[Bitcoin Oz]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

[bg002h]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

Not a bad idea. Another idea (unrelated) would be to print a change address QR code on the bill.

This sure is a lot easier than building it's electronic equivalent!

[Gyrsur]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

Not a bad idea. Another idea (unrelated) would be to print a change address QR code on the bill.

This sure is a lot easier than building it's electronic equivalent!

like this idea! imagine you want to go out with your girl and print out before a 10BTC banknote with an individuel change adresse on it. go out to a restaurant, leave blackberry at home, have a good time and leave the 10BTC banknote there. next day the change is on your individual address back and you give the restaurant 5 stars on web and your girl gave you what she want's to give... 

[Gyrsur]

very exciting! want to print out my five 1BTC banknotes soon and put it under the mattress... 

a good idea is also to have different colors for different BTC banknotes... 1BTC, 5BTC, 10BTC, 20BTC, 50BTC, 100BTC

[mobile4ever]

Do the QR codes work with any mobile digital wallets? Android has one.


http://www.wired.com/gadgetlab/2011/07/bitcoin-android-app/

[scribe]

Looking lovely - just as with the coins, I think the big bonus here is it makes Bitcoin look Gooood.

I guess they're not too different from Bitcoin cheques, except if the private key is available, these are maybe a bit more transferable/disposable/usable as a paper wallet?

Also like the idea of a keyfob with QR codes on. Might be a good excuse to finally get out that keychain digital photo frame I bought cheap ages ago...

[casascius]

Looking lovely - just as with the coins, I think the big bonus here is it makes Bitcoin look Gooood.

I guess they're not too different from Bitcoin cheques, except if the private key is available, these are maybe a bit more transferable/disposable/usable as a paper wallet?

Also like the idea of a keyfob with QR codes on. Might be a good excuse to finally get out that keychain digital photo frame I bought cheap ages ago...

They are exactly like bitcoin cheques, except you print them yourself, fund them yourself, there's no hologram, and you throw them away once the private key has been shared.

[unclemantis]

Looking lovely - just as with the coins, I think the big bonus here is it makes Bitcoin look Gooood.

I guess they're not too different from Bitcoin cheques, except if the private key is available, these are maybe a bit more transferable/disposable/usable as a paper wallet?

Also like the idea of a keyfob with QR codes on. Might be a good excuse to finally get out that keychain digital photo frame I bought cheap ages ago...

They are exactly like bitcoin cheques, except you print them yourself, fund them yourself, there's no hologram, and you throw them away once the private key has been shared.

They are cheques. I would like to have the private key signed with a passphrase though. I have asked the creator of bitaddress.org for the option of a passphrase aes encrypted private key but he does not see the value in this. He is more focused on the brain wallet.

[casascius]

They are cheques. I would like to have the private key signed with a passphrase though. I have asked the creator of bitaddress.org for the option of a passphrase aes encrypted private key but he does not see the value in this. He is more focused on the brain wallet.

No one has really standardized a way to encode and decode a key with a password.

I proposed one in the Wiki - though not with AES - it would encode a simple XOR of the private key with the hash of the password.  I consider AES the wrong tool for the job - AES is great for encrypting a stream of blocks of data - and all the overhead needed to use it properly (key, ciphertext, possibly an IV) would instantly double or triple the length of the key code.

I might implement this in Casascius Bitcoin Address Utility as a reference, and then see who else follows... if nothing else, the same utility could be used to decode password-protected private keys into normal ones.

[ErebusBat]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

Not a bad idea. Another idea (unrelated) would be to print a change address QR code on the bill.

This sure is a lot easier than building it's electronic equivalent!

This is a bad idea (as the notes are currently designed). 

The private key is gone on first spend so you don't really want to have it hanging out.

[Gyrsur]

Looking lovely - just as with the coins, I think the big bonus here is it makes Bitcoin look Gooood.

I guess they're not too different from Bitcoin cheques, except if the private key is available, these are maybe a bit more transferable/disposable/usable as a paper wallet?

Also like the idea of a keyfob with QR codes on. Might be a good excuse to finally get out that keychain digital photo frame I bought cheap ages ago...

They are exactly like bitcoin cheques, except you print them yourself, fund them yourself, there's no hologram, and you throw them away once the private key has been shared.

be 100 percent with you. people can print it out for themselves if needed and put it in a purse so the private key is hidden. when they give the note away the receiver has to take care of give back the change also as notes or via network...

[Gyrsur]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

Not a bad idea. Another idea (unrelated) would be to print a change address QR code on the bill.

This sure is a lot easier than building it's electronic equivalent!

This is a bad idea (as the notes are currently designed).  

The private key is gone on first spend so you don't really want to have it hanging out.

you have to have an addition like vote the receiver via web if he is trustable. if you think of an restaurant or a shop it is a great idea to vote. and there must be a second public key for the changes on the note so that the receiver can give the change back. please have in mind if you give the note (private key) away the whole amount is giving away. you have also to hide the private key in an easy way like putting it in a envelope or purse because there cannot be a complicated mechanism of hiding the private key. everybody should be able to print it out.

[n8rwJeTt8TrrLKPa55eU]

The paper note should have smaller tear off strips of different value so as you use it the note gets smaller over time.
You could call them "bits" of paper....

Love this.  It would tie into a similar solution and terminology developed in the Americas with commodity money:

"A fractional application of the Spanish milled dollar by the colonists was the origin of many terms identified with our current denominations. The English referred to a real as a “bit”, a usage that was subsequently carried over into American commercial outlets and on into the marketplaces until it became a standard term of reference. Since “piece of eight” describes a coin of eight units or pieces, it is only natural that half a dollar would be referred to as four reales or four bits and by the same token, a quartered section of two reales was called two bits. Half of a quartered section was a real or one bit and, divided equally, a bit produced two picayunes valued at six and one-half cents each. When a quartered section was divided unequally on a forty-to-sixty proportion of the quarter section the smaller piece was a short bit valued at ten cents and the larger piece was a long bit valued at fifteen cents."

[Gyrsur]

is this the reason to have quarter coins (0.25) available with dollar?

[casascius]

They are cheques. I would like to have the private key signed with a passphrase though. I have asked the creator of bitaddress.org for the option of a passphrase aes encrypted private key but he does not see the value in this. He is more focused on the brain wallet.

No one has really standardized a way to encode and decode a key with a password.

I proposed one in the Wiki - though not with AES - it would encode a simple XOR of the private key with the hash of the password.  I consider AES the wrong tool for the job - AES is great for encrypting a stream of blocks of data - and all the overhead needed to use it properly (key, ciphertext, possibly an IV) would instantly double or triple the length of the key code.

I might implement this in Casascius Bitcoin Address Utility as a reference, and then see who else follows... if nothing else, the same utility could be used to decode password-protected private keys into normal ones.

Actually I thought of a reason why to use AES instead of XOR, even if it were with no IV, and the key were a simple hash of the password (to prevent lengthening of the string).  It occurred to me that someone having an encrypted private key along with a decrypted version of that private key would be able to deduce the password hash if XOR was used, which could then be used to decrypt other private keys encrypted with that same password, without knowing the password.  AES would probably stop this.

So, back to square one: the actual key standard and encryption method needs to be worked out before Bitaddress.org or something similar can really implement it.

[Meatpile]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

[ErebusBat]

Actually I thought of a reason why to use AES instead of XOR, even if it were with no IV, and the key were a simple hash of the password (to prevent lengthening of the string).  It occurred to me that someone having an encrypted private key along with a decrypted version of that private key would be able to deduce the password hash if XOR was used, which could then be used to decrypt other private keys encrypted with that same password, without knowing the password.  AES would probably stop this.

So, back to square one: the actual key standard and encryption method needs to be worked out before Bitaddress.org or something similar can really implement it.

Also an IV and whatnot isn't a real big concern, just use KeyStreching http://en.wikipedia.org/wiki/Key_stretching, specifically PBKDF2

[Gyrsur]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

not if you think about a restaurant or a shop. they have always there equipment on. if you want to buy on a flea market for examble the seller of goods have to check if the notes are funded via a mobile and give back the change notes. the big advantage should be that one party are able to take bitcoins with it offline in notes. and sure you can easily hoard it at home as BTC notes.

[RDWHAHB]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

The recipient needs internet access. I plan to use this method if I for local, in person sale of my bitcoins for cash.

For example: I have a localbitcoin ad to sell 10BTC. Someone responds and we meet wherever he is comfortable with his internet access. I print and fund a 10BTC bill before going out to meet him/her. We exchange cash for paper, and they transfer the coin to there own wallet. Yes, they should have access, but I don't need anything other than my printed coin. I don't have a smart phone so this is ideal for me.

[Gyrsur]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

exactly this is how the process should work.

[Gyrsur]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

The recipient needs internet access. I plan to use this method if I for local, in person sale of my bitcoins for cash.

For example: I have a localbitcoin ad to sell 10BTC. Someone responds and we meet wherever he is comfortable with his internet access. I print and fund a 10BTC bill before going out to meet him/her. We exchange cash for paper, and they transfer the coin to there own wallet. Yes, they should have access, but I don't need anything other than my printed coin. I don't have a smart phone so this is ideal for me.

yeah also if you think about gifts. you want to spread the idea of bitcoin within your family and spend gifts of BTC bills to all. so they don't need to check if the bills are funded because they trust in you.

[unclemantis]

0.001BTC

1JkoYMWCEE65DyjHBFpC6Gg7YWQvc26FXz


AES 128 PASSPHRASE ENCRYPTED PRIVATE KEY

[CoinDiver]

The problem with self printed bills is always going trust. This is where it would be useful the have trusted third party vendors issuing paper currency, with bitcoins to back the value. Hide the private key under a tamper evident hologram just like the coins. You should be able to get these printed for pennies.

There is nothing wrong with having a central issuer of paper money... the problem is when they have an effect on the value of that money. This would not be the case here.

These self printed bills would be great for use where both parties trust the other.

[Dansker]

This stuff is begging for an article in The Bitcoin Magazine!

[casascius]

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

Mainly because of the speed with which you can make the transfer.  You can pull out paper bills and pay in single-digit seconds, just like cash.  When everybody has a smartphone and could pull it out and wave it and pay with under 10 seconds, my proposal will be meritless.  But not everybody has a smartphone, and those that do will spend 30-60 seconds opening the app, scanning a code, initiating a transaction, and waiting for the merchant POS to detect the transaction, and those seconds are very long when you're holding up the line at the checkout counter figuring out your Bitcoin payment and wishing you just swiped your debit card.

[tonto]

I'm a newbie when it comes to QR codes, but I was wondering if there's enough 'room' in the QR code so that if you had a reader that would read those QR codes on the bills and send any remaining change to an address in the QR code?  That way you could easily tear/up and throw away the original bill, and not have to worry about security issues since that amount would then be zero.  Then your change is back to your wallet (either home or mobile).
 
Obviously the QR readers (POS?) and software would have to know how to deal with the left over but then you could reprint for the next time you went out, or maybe a mobile QR maker could make your QR code when you're ready to go back up to the bar and get a refill beer (assuming you're out of your pre-printed bills)?
 
I love your physical ideas casascius, and wondered if something like this might be thought about?

[casascius]

I'm a newbie when it comes to QR codes, but I was wondering if there's enough 'room' in the QR code so that if you had a reader that would read those QR codes on the bills and send any remaining change to an address in the QR code?  That way you could easily tear/up and throw away the original bill, and not have to worry about security issues since that amount would then be zero.  Then your change is back to your wallet (either home or mobile).
 
Obviously the QR readers (POS?) and software would have to know how to deal with the left over but then you could reprint for the next time you went out, or maybe a mobile QR maker could make your QR code when you're ready to go back up to the bar and get a refill beer (assuming you're out of your pre-printed bills)?
 
I love your physical ideas casascius, and wondered if something like this might be thought about?

There is room, and this could be implemented as one way to specify the change address.  (e.g. it includes a "changeto" section, so if the user doesn't scan a different specific change address, the changeto one is used by default, which points to the home wallet).

[unclemantis]

Mike. Do you like my example that I posted above? The passphrase is pretty obvious.

[casascius]

OK, Windows users can download my current version of the utility and print Bitcoin notes!  It's on the menu under Tools - Paper Wallet Generator.

Binary and source is included.  https://casascius.com/btcaddress.zip

Requires .NET Framework 4.0 (which should be present on any recent Windows system).  Compiling Source requires Visual Studio 2010 (and probably will work with the free versions of Microsoft's C# compiler)

Note there is a PNG file that contains the graphic used on the notes - you can change this with any other png file with the same aspect ratio.

EDIT: I forgot it also uses the Ubuntu font, and if you don't have this installed, it will probably substitute some other font on your system.

[unclemantis]

OK, Windows users can download my current version of the utility and print Bitcoin notes!  It's on the menu under Tools - Paper Wallet Generator.

Binary and source is included.  https://casascius.com/btcaddress.zip

Requires .NET Framework 4.0 (which should be present on any recent Windows system).

Note there is a PNG file that contains the graphic used on the notes - you can change this with any other png file with the same aspect ratio.

Downloading now.. will give it a shot.

[casascius]

Mike. Do you like my example that I posted above? The passphrase is pretty obvious.

I scanned it and got U2FsdGVkX1+GmmpNCQBb+zrHyMSmAQsnk4heY+SbUssaTj+d+E2Vd5eb7D30CAdr3HFSk6hifRqQDGWputN7qz6tdyHe/2YyNV2ElfZ7cXg= but didn't make any effort to guess at the passphrase.  I am also thinking that going forward, there should be a regular format for password-protected keys (i.e. instead of something looking like 5JVpCLEMPARHYy6zVu78PR9Tc7KvLhCBLfCib3qRt1KQTxFYMsP, it would be more like 6pEKRVv4ELhVm8nGJjQNmsoLBjYDXuuZG8RAzht9Z8L6TSYJaf1 where 6p means this is a passworded priv key).

[unclemantis]

Mike. Do you like my example that I posted above? The passphrase is pretty obvious.

I scanned it and got U2FsdGVkX1+GmmpNCQBb+zrHyMSmAQsnk4heY+SbUssaTj+d+E2Vd5eb7D30CAdr3HFSk6hifRqQDGWputN7qz6tdyHe/2YyNV2ElfZ7cXg= but didn't make any effort to guess at the passphrase.  I am also thinking that going forward, there should be a regular format for password-protected keys (i.e. instead of something looking like 5JVpCLEMPARHYy6zVu78PR9Tc7KvLhCBLfCib3qRt1KQTxFYMsP, it would be more like 6pEKRVv4ELhVm8nGJjQNmsoLBjYDXuuZG8RAzht9Z8L6TSYJaf1 where 6p means this is a passworded priv key).

That does seem to be a lot shorter. I am welcome to any standardization that you can bring to the base.

[Gyrsur]

OK, Windows users can download my current version of the utility and print Bitcoin notes!  It's on the menu under Tools - Paper Wallet Generator.

Binary and source is included.  https://casascius.com/btcaddress.zip

Requires .NET Framework 4.0 (which should be present on any recent Windows system).  Compiling Source requires Visual Studio 2010 (and probably will work with the free versions of Microsoft's C# compiler)

Note there is a PNG file that contains the graphic used on the notes - you can change this with any other png file with the same aspect ratio.

EDIT: I forgot it also uses the Ubuntu font, and if you don't have this installed, it will probably substitute some other font on your system.

+100 Thank you very much! Need a while to play around with it.

[OpenBNS]

Thanks for posting this.  I just printed 8 Bitcoin bank notes.  No problems.

[SgtSpike]

Love the looks!

I do like the idea of having "tear off" private keys in a variety of denominations all on the same piece of paper.  Maybe 10x 0.1 BTC tearoffs, 5x .25 BTC tearoffs, 2x 0.5 BTC tearoffs on a small one, and 10x 1 BTC tearoffs, 5x 2 BTC tearoffs, and 2x 5 BTC tearoffs on a large one.  Then, you just pull out one of the two bills and tear off the relevant denomination when a payment needs to be made.

How small could the private key QR code be made while still being readable by the typical QR reader?  Seems as though you'd need just three things on the tearoff:  A QR code for private key, a firstbits address for verifying that the address is funded, and a denomination (such as 0.25 BTC) on it somewhere to identify how much is SUPPOSED to be in that address.  If you could fit 17+ tearoffs on the same bill, it would be awesome. 

[Meatpile]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

The recipient needs internet access. I plan to use this method if I for local, in person sale of my bitcoins for cash.

For example: I have a localbitcoin ad to sell 10BTC. Someone responds and we meet wherever he is comfortable with his internet access. I print and fund a 10BTC bill before going out to meet him/her. We exchange cash for paper, and they transfer the coin to there own wallet. Yes, they should have access, but I don't need anything other than my printed coin. I don't have a smart phone so this is ideal for me.

Offline bitcoin transactions will never work unless you have strong cryoptography based hardware, and the coins are held by an escrow third party. (escrow would need to hold those funds for an amount of time until both parties hardware has checked in with the master server)

Unless you are talking about just transacting with your well trusted friends, there is always a breakdown of trust in multiple locations:

- So only the recipient has internet access in your example: he doesnt want to hand you cash until he sees the private key you are handing over actually has money in it. So he can scan it, hand it back and say it was already empty and runs away. Well he just stole the coins.
- (Well just let him scan the public key and not the private one) well ok in that case you can scam him by NOT putting the REAL private key under your thumb
- He doesnt want to hand you cash until he knows he can get bitcoins, you dont want him to scan any private key until you have cash


Lets pretend for a minute none of that matters, say casascius physical coins have a hidden private key under a hologram... Well if casascius wants to make any profit at all he has to sell them for more than they are worth. This means that if it is at all possible to make a fake, that costs less than it is worth, the market WILL get flooded with fakes.

Now there is one scenario that may work: if it costs MORE to produce a physical bitcoin representation than it is worth. In that case you wouldn't want to make a fake that costs more than its worth.  But why on earth would anyone do such a thing? They can not make profit and lose money doing it?

[casascius]

- So only the recipient has internet access in your example: he doesnt want to hand you cash until he sees the private key you are handing over actually has money in it. So he can scan it, hand it back and say it was already empty and runs away. Well he just stole the coins.

By the same token, you could hand him a $20 bill, and he could put it in the register, close the drawer, and then claim it was a $10, or that you gave him nothing at all.  Your word against his.  It's bad for business.  At least where I shop.

Lets pretend for a minute none of that matters, say casascius physical coins have a hidden private key under a hologram... Well if casascius wants to make any profit at all he has to sell them for more than they are worth. This means that if it is at all possible to make a fake, that costs less than it is worth, the market WILL get flooded with fakes.

That could actually happen, but so far it has not.  It's just as possible to make real physical bitcoins and make a profit.  At DefCon, I walked around wearing a T-shirt that says "I SELL PHYSICAL BITCOINS", and was charging $15 cash for 1BTC coins worth under $9 at MtGox, selling to anyone who'd stop me in the halls.  What's better, the $6 I could make consistently by marking up the coin, or the $9 I could scam people for until I was shut down?  Meat may be tasty but you don't slaughter a cash cow.

Now there is one scenario that may work: if it costs MORE to produce a physical bitcoin representation than it is worth. In that case you wouldn't want to make a fake that costs more than its worth.  But why on earth would anyone do such a thing? They can not make profit and lose money doing it?

The economics of producing holograms are such that it's a big investment to get the holographic master made.  On the flip side, if you start scamming people, you'll be left with a bunch of coin materials you can't move because people have caught on to your scam and stopped buying.

In the end, you're right: somebody enterprising could put their efforts into counterfeiting my coins and it would be disappointing.  But so far that hasn't happened, and they continue to be a great gift and promotional tool for Bitcoin.

[unclemantis]

I will use one this Friday when giving a donation to my local hacker space. I guess I will have to fold in in half a few times before placing it in the donation jar or hand it directly to the head hacker

[BitLucky]

I will use one this Friday when giving a donation to my local hacker space. I guess I will have to fold in in half a few times before placing it in the donation jar or hand it directly to the head hacker

That's a cool idea for these notes!

[mobile4ever]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

You are right, but since mobile devices are usually connected to the web in some way these days, that should not be a problem. But... since this person is not answering if it works with mobiles or not... no one will know, eh?

[RDWHAHB]

The recipient needs internet access. I plan to use this method if I for local, in person sale of my bitcoins for cash.

For example: I have a localbitcoin ad to sell 10BTC. Someone responds and we meet wherever he is comfortable with his internet access. I print and fund a 10BTC bill before going out to meet him/her. We exchange cash for paper, and they transfer the coin to there own wallet. Yes, they should have access, but I don't need anything other than my printed coin. I don't have a smart phone so this is ideal for me.

[...]
- So only the recipient has internet access in your example: he doesnt want to hand you cash until he sees the private key you are handing over actually has money in it. So he can scan it, hand it back and say it was already empty and runs away. Well he just stole the coins.
- (Well just let him scan the public key and not the private one) well ok in that case you can scam him by NOT putting the REAL private key under your thumb
- He doesnt want to hand you cash until he knows he can get bitcoins, you dont want him to scan any private key until you have cash

Have you never bought or sold anything in person? If you put the coin there, you know it's there. The other party saying it isn't and running off is no different than just plain stealing it in the first place. Actually, you even have proof that you funded the address.

If that requires escrow, everything requires escrow.

[n8rwJeTt8TrrLKPa55eU]

is this the reason to have quarter coins (0.25) available with dollar?

That's right, some of the fractional coin denominations were inherited from the time when the coins were physically cut into pieces to make change.  And it's also the reason why stocks in the USA were, until fairly recently, quoted fractionally using units of 1/8ths, instead of arbitrary decimal digits.

[naypalm]

Very cool! 

[unclemantis]

0.001BTC

1JkoYMWCEE65DyjHBFpC6Gg7YWQvc26FXz


AES 128 PASSPHRASE ENCRYPTED PRIVATE KEY

Looks like my bit cheque still has a balance. Come on people. If you did a search on this forum you will see I used the same passphrase as my last contest. It is ripe for the picking at 119 confirmations.

[Clark]

Looks like my bit cheque still has a balance. Come on people. If you did a search on this forum you will see I used the same passphrase as my last contest. It is ripe for the picking at 119 confirmations.

 

[BoardGameCoin]

I've been experimenting with these via your BitAddress utility. I think they're useful as is for a stylish paper wallet, but here's some suggestions:

• The key text is facing the wrong way. I had to fold the bill over to read the public key without the private key showing. If the key text was rotated 180 degrees, then I could cover the private key with my hand while I enter the public key
• The private key QR-Code is a bit large (I think you already commented on this)
• The public key text is a bit too small
• The bill as a whole seems a bit large to me. It might be nice to do something like four to a sheet and just make them a bit smaller.

I'm already grateful for where they are now, and I've gotten off my duff and made some paper wallets as a result. Thanks a bunch!

-bgc

[casascius]

I've been experimenting with these via your BitAddress utility. I think they're useful as is for a stylish paper wallet, but here's some suggestions:

• The key text is facing the wrong way. I had to fold the bill over to read the public key without the private key showing. If the key text was rotated 180 degrees, then I could cover the private key with my hand while I enter the public key
• The private key QR-Code is a bit large (I think you already commented on this)
• The public key text is a bit too small
• The bill as a whole seems a bit large to me. It might be nice to do something like four to a sheet and just make them a bit smaller.

I'm already grateful for where they are now, and I've gotten off my duff and made some paper wallets as a result. Thanks a bunch!

-bgc

I agree with you on all counts, but might leave the private QR code large just having seen how they wear down in my pocket (or might make it a user selectable option).  I'd like to make the bill size an option, and also have different bill colors an option as well.  I will probably make it auto-sense the paper size and fill the sheet, right now it is just hard coded to 3 to a page and doesn't even consider the paper size/orientation.

[mpfrank]

OK, Windows users can download my current version of the utility and print Bitcoin notes!  It's on the menu under Tools - Paper Wallet Generator.

Binary and source is included.  https://casascius.com/btcaddress.zip

Requires .NET Framework 4.0 (which should be present on any recent Windows system).  Compiling Source requires Visual Studio 2010 (and probably will work with the free versions of Microsoft's C# compiler)

Note there is a PNG file that contains the graphic used on the notes - you can change this with any other png file with the same aspect ratio.

EDIT: I forgot it also uses the Ubuntu font, and if you don't have this installed, it will probably substitute some other font on your system.

Maybe I'm being dense, but, I don't see a Tools menu.  At the top there is only a button that says "Wallet Generator" and a button that says "Help."  The Wallet Generator button brings up another window that says "Paper Wallet Generator", but it only prints a plain-text list of keys, not the pretty bank note.  Did you revert your ZIP file to an older version?  The one I downloaded from the above URL didn't include the source either...

[Kupsi]

Maybe I'm being dense, but, I don't see a Tools menu.  At the top there is only a button that says "Wallet Generator" and a button that says "Help."  The Wallet Generator button brings up another window that says "Paper Wallet Generator", but it only prints a plain-text list of keys, not the pretty bank note.  Did you revert your ZIP file to an older version?  The one I downloaded from the above URL didn't include the source either...

I can confirm that the zip file has changed to an older version.

[casascius]

Sorry about that, I didn't realize I accidentally reverted it to an earlier version.  I sent an update to my website and didn't realize that an old btcaddress.zip was actually in the update and overwrote what I had posted.

I have restored the newer version.

[mpfrank]

I have restored the newer version.

Thanks.  So the "Denomination" option does not actually do anything yet?  I didn't notice any difference in how the bills were printed...

[Meatpile]

- So only the recipient has internet access in your example: he doesnt want to hand you cash until he sees the private key you are handing over actually has money in it. So he can scan it, hand it back and say it was already empty and runs away. Well he just stole the coins.

By the same token, you could hand him a $20 bill, and he could put it in the register, close the drawer, and then claim it was a $10, or that you gave him nothing at all.  Your word against his.  It's bad for business.  At least where I shop.

Lets pretend for a minute none of that matters, say casascius physical coins have a hidden private key under a hologram... Well if casascius wants to make any profit at all he has to sell them for more than they are worth. This means that if it is at all possible to make a fake, that costs less than it is worth, the market WILL get flooded with fakes.

That could actually happen, but so far it has not.  It's just as possible to make real physical bitcoins and make a profit.  At DefCon, I walked around wearing a T-shirt that says "I SELL PHYSICAL BITCOINS", and was charging $15 cash for 1BTC coins worth under $9 at MtGox, selling to anyone who'd stop me in the halls.  What's better, the $6 I could make consistently by marking up the coin, or the $9 I could scam people for until I was shut down?  Meat may be tasty but you don't slaughter a cash cow.

Now there is one scenario that may work: if it costs MORE to produce a physical bitcoin representation than it is worth. In that case you wouldn't want to make a fake that costs more than its worth.  But why on earth would anyone do such a thing? They can not make profit and lose money doing it?

The economics of producing holograms are such that it's a big investment to get the holographic master made.  On the flip side, if you start scamming people, you'll be left with a bunch of coin materials you can't move because people have caught on to your scam and stopped buying.

In the end, you're right: somebody enterprising could put their efforts into counterfeiting my coins and it would be disappointing.  But so far that hasn't happened, and they continue to be a great gift and promotional tool for Bitcoin.

Well there are two different realms here: you are selling these physical bitcoins for novelty and its neat and mostly direct to user sales. Of course you wouldnt sell fakes. But if the whole idea is to have random people trade random "physical bitcoins" all over the world to actually do business, then its not a novelty anymore and real security is very important.

I hate when people fallback to comparing bitcoin thefts to "just like cash". Its a bullshit non-argument. You can't report theft of your intangible digital money to any authority right now, possibly never in the future will it be respected by law enforcement. This is very clear how all the current theives get away scott free.  And secondly the BENEFIT of bitcoin is that it is digital, so we should be able to use this to layer hardware security ontop of it so it is better than cash. And lastly, if it is succeptable to ALL of the current problems that cash theft is, plus all the hacking losses, no economy, etc etc... then fuck it why bother.

[unclemantis]

Looks like my bit cheque still has a balance. Come on people. If you did a search on this forum you will see I used the same passphrase as my last contest. It is ripe for the picking at 119 confirmations.

 

And we have a winner!

[casascius]

I have restored the newer version.

Thanks.  So the "Denomination" option does not actually do anything yet?  I didn't notice any difference in how the bills were printed...

Not on the version I posted - ironically, the only place it prints is on the 16-to-a-page wallets.  I was experimenting with cutting the page into 16 little "bills" as an initial test.  The next time I update my website though, it will print on the bill.

There is one other place it is used, and that's if you do the "sendmany" export.  The idea behind it is the text file is a command line script that funds the wallets in a batch.  The funding command needs a denomination so... it is used there.

[andrehorta]

It´s cool!

I would like to use in Brazil.

[bg002h]

I assume it's the private key that's under your finger. Without any additional security measures, how can one be sure that a paper coin is unspent?

The idea with these is that the receiver of a bill scans the private key, immediately moving the funds to another address. The bill can then be discarded.

So stupid... if you NEED INTERNET ACCESS to verify it, then why is it in paper in the first place?

This is only useful for personal offline backup, never to be used for public transfer.

I take my Internet connection with me everywhere I go...

[bg002h]

The problem with self printed bills is always going trust. This is where it would be useful the have trusted third party vendors issuing paper currency, with bitcoins to back the value. Hide the private key under a tamper evident hologram just like the coins. You should be able to get these printed for pennies.

There is nothing wrong with having a central issuer of paper money... the problem is when they have an effect on the value of that money. This would not be the case here.

These self printed bills would be great for use where both parties trust the other.

No trust required. Verify the bill before accepting...you aren't trusting the bill to be valid, you are verifying the private key is backed by Bitcoins....

[tiberiandusk]

For the bills a bill reader like on vending machines could be modified to read the QR code and import the private key to the store's wallet. Once it is verified the bill could be shredded and recycled. For change they could use a heat printer to spit out a QR code with the remaining balance. It would be awesome if you could incorporate your program into the actual Bitcoin client so you just tell it what denomination bills you want and it would print them out. The client would show your wallet balance and the balance of your printed bills which would be updated when someone claims the private key when you spend a bill.

[casascius]

The vending machine could also return change to the bill. Or to another BTC address provided by the customer via the QR scanner.  No printer needed.

[tiberiandusk]

Yeah I didn't even think of that. It would be nice for it to print the remaining balance on it to make it easier to remember what it's actually still worth. I would love to have a 15.8686493 denomination bill. :-P

[dentldir]

How do you verify that a private key is valid and backs a particular address?  Can this be done offline? 

Every time I think I completely understand Bitcoin I hit questions like this.  I know the client will do it for you, but I'd like to hold up my phone and have is say yes or no to a paper note instantly and without a net connection.

[dentldir]

Then of course I'd still need a net connection to check the balance...

But still, is offline private key/address verification possible with out the client?

[rebuilder]

Then of course I'd still need a net connection to check the balance...

But still, is offline private key/address verification possible with out the client?

I'm not sure what you mean. Checking that a private key is valid and matches a given public address? This should be possible, but not very useful, since what you'd really be interested in is whether the address holds funds. And even if it did, being offline you could not transfer the funds to a key only you control.

[dentldir]

I was thinking of what a scammer would do with the ability to print Bitcoin bills for an in person transaction:

1) Print a bill with a corrupted private key and a real address
2) Keep a copy of the real private key
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Walk away with your goods and Bitcoins
6) The victim wont know that the private key is useless until they are online and try and import it

Being able to confirm that the private key actually connects to the address gets you some protection against this.

The other scheme is:

1) Print a bill with a good private key and a real address
2) Import the private key to an online wallet
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Right after they see its funded, pretend you are checking a text message, but send the money back to yourself with your phone.
6) Walk away with everything

I'm not sure how to get protection against this one.

[casascius]

I was thinking of what a scammer would do with the ability to print Bitcoin bills for an in person transaction:

1) Print a bill with a corrupted private key and a real address
2) Keep a copy of the real private key
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Walk away with your goods and Bitcoins
6) The victim wont know that the private key is useless until they are online and try and import it

Being able to confirm that the private key actually connects to the address gets you some protection against this.

The other scheme is:

1) Print a bill with a good private key and a real address
2) Import the private key to an online wallet
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Right after they see its funded, pretend you are checking a text message, but send the money back to yourself with your phone.
6) Walk away with everything

I'm not sure how to get protection against this one.

In each case, Step 4 is where things went wrong.  The person receiving the bill should sweep the address immediately and take control of the funds being presented to him in step 4 by sweeping them to another address, so he will know that the funds are there and can't disappear.

[dentldir]

If you corrupt the private key on the bill and keep the real one to yourself, the victim won't know until they import it into the client right?

But if you mathematically prove the private key matches the address, then this scenario isn't an issue.

[casascius]

If you corrupt the private key on the bill and keep the real one to yourself, the victim won't know until they import it into the client right?

But if you mathematically prove the private key matches the address, then this scenario isn't an issue.

The "victim" should be importing it into the client the moment he gets it, and ought to know whether or not it's any good before accepting it.

[SgtSpike]

If you corrupt the private key on the bill and keep the real one to yourself, the victim won't know until they import it into the client right?

But if you mathematically prove the private key matches the address, then this scenario isn't an issue.

That's why it would be incredibly stupid of the victim to not immediately move the funds to a different account.

Casascius coins can work well for person-to-person transactions where there is no possibility to move the funds immediately, but these printed bills are only useful when the receiving entity has the ability to create a transaction with the newly acquired private key at the moment the transaction happens.  For example, in a retail store, the clerk would scan the private key, the system would automatically and immediately create a transaction to move the funds to it's main account, the clerk would wait a few seconds to be sure that the new transaction has been properly broadcasted to the network, and then hand the customer his receipt.

Oh, and as long as we're talking about private keys and change addresses, as long as the customer saw the cashier hand him his receipt without scanning a private key, couldn't a change address just be printed on the receipt?  Then, the next transaction that the customer makes, perhaps at a different store, he can just let them scan the new address where he received his change.

[Stephen Gornick]

The "victim" should be importing it into the client the moment he gets it, and ought to know whether or not it's any good before accepting it.

Not just importing it but spending it (sweep) to another address from the wallet.

Mt. Gox mobile client does this.

A motivated mobile app developer can probably sell a few copies of an app (and/or mobile enabled web-site) that does nothing more than scan the "spend" (private key) of a bitcoin banknote I received, do a second scan for the "load" (on one of my own notes), build a transaction to spend the funds and submit it (e.g., to blockchain's pushtx), and to display the amount + success / failure (i.e., wasn't a double spend.)

This lets me have the value stored on these bitcoin banknotes at all times, with no reliance on an EWallet.  And since the mobile wallet apps and web-based EWallets do not yet have the ability to redeem and sweep, this limited functionality app would at least make these notes functional now, not in some vision of how things could work down the road.

[koin]

Windows users can download my current version of the utility and print Bitcoin notes!

is anyone building something similar for mac or linux users?

[bg002h]

I was thinking of what a scammer would do with the ability to print Bitcoin bills for an in person transaction:

1) Print a bill with a corrupted private key and a real address
2) Keep a copy of the real private key
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Walk away with your goods and Bitcoins
6) The victim wont know that the private key is useless until they are online and try and import it

Being able to confirm that the private key actually connects to the address gets you some protection against this.

The other scheme is:

1) Print a bill with a good private key and a real address
2) Import the private key to an online wallet
3) Fund the address
4) Show the person you are paying that the Bitcoin address is funded
5) Right after they see its funded, pretend you are checking a text message, but send the money back to yourself with your phone.
6) Walk away with everything

I'm not sure how to get protection against this one.

The bills aren't meant to circulate. You give the private key away and the new owner transfers the coins immediately or takes your contact info in case they decide to transfer later and it bounces...like a check that has the option of being instantly cashed.

[unclemantis]

I am out of black ink but everything printed good to me! Just looks faded since I have all the colors but black

[SgtSpike]

The "victim" should be importing it into the client the moment he gets it, and ought to know whether or not it's any good before accepting it.

Not just importing it but spending it (sweep) to another address from the wallet.

Mt. Gox mobile client does this.

A motivated mobile app developer can probably sell a few copies of an app (and/or mobile enabled web-site) that does nothing more than scan the "spend" (private key) of a bitcoin banknote I received, do a second scan for the "load" (on one of my own notes), build a transaction to spend the funds and submit it (e.g., to blockchain's pushtx), and to display the amount + success / failure (i.e., wasn't a double spend.)

This lets me have the value stored on these bitcoin banknotes at all times, with no reliance on an EWallet.  And since the mobile wallet apps and web-based EWallets do not yet have the ability to redeem and sweep, this limited functionality app would at least make these notes functional now, not in some vision of how things could work down the road.

Even better, the app should require no user intervention besides scanning the Bitcoin note.  In the initial setup of the app, you give the app a Bitcoin address or series of addresses to sweep funds into.  If you give it a series, it'll use them each only once, unless it runs out, at which point it'll start at the first address again.  It automatically does the sweeping for you as soon as the private key is scanned.  A one-step receipt.

[casascius]

Windows users can download my current version of the utility and print Bitcoin notes!

is anyone building something similar for mac or linux users?

I am hoping these features get added into BitAddress.org so there is a browser-based platform-independent solution.

[Stephen Gornick]

Even better, the app should require no user intervention besides scanning the Bitcoin note.  In the initial setup of the app, you give the app a Bitcoin address or series of addresses to sweep funds into.  

I have a specific use case where the target bitcoin address is not necessarily my own.

Perhaps I pull up to the automated car wash which accepts bitcoin for payment.  It spits out a ticket with a QR code for me to send my payment to.  

Let's assume I have a smartphone, iPad, or whatever, but no bitcoin wallet on it. I don't even need data service or SMS even. [Edited]

So the price of the wash is 0.8 BTC.  In my wallet today, I carry a few $20s.  So similarly, let's say I carry a few 2.0 BTC banknotes in it.

I pull out a 2.0 BTC bitcoin banknote from my pocket, using this app on my smartphone I scan the banknote for the "From:" then scan the QR code from the pay terminal ticket for the "To:".  

The car wash terminal then spits out a receipt and on the receipt is the change in the form of a QR code, a private key, funded with 1.2 BTC.

So then using the app on my smartphone I scan that "Spend" QR code from the receipt as the "From:" and then scan the "Load" QR code from the next 2.0 BTC bitcoin banknote in my wallet as the "To:".

So this app is just a utility, scan the "From:", scan the "To:", spend the funds, done.   There's never any bitcoins stored in a wallet on my mobile or with an EWallet.

[ralree]

Then of course I'd still need a net connection to check the balance...

But still, is offline private key/address verification possible with out the client?

I'm not sure what you mean. Checking that a private key is valid and matches a given public address? This should be possible, but not very useful, since what you'd really be interested in is whether the address holds funds. And even if it did, being offline you could not transfer the funds to a key only you control.

I think the question is "how do I know the private key that I can't see actually unlocks the address on the bill?"  This is exactly the problem with any physical bitcoins you can make at home - the person receiving them has to trust that there's not just a happy face under the hologram instead of a privkey.

[adamstgBit]

Windows users can download my current version of the utility and print Bitcoin notes!

link?

[casascius]

Windows users can download my current version of the utility and print Bitcoin notes!

link?

Earlier in thread, should be:

https://casascius.com/btcaddress.zip

[goxed]

very nice! Can I have them?

I'm hoping yes... I'm planning on releasing the source code I used to print these.

Thanks a lot!

[pointbiz]

Windows users can download my current version of the utility and print Bitcoin notes!

is anyone building something similar for mac or linux users?

I am hoping these features get added into BitAddress.org so there is a browser-based platform-independent solution.

I don't have a time frame but I am working on it.

The use case for these fancy paper wallets is the full set of use cases for paper wallets with the addition of being able to give BTC as a gift certificate. Also less likely someone would throw out a paper wallet by accident when it looks like something of value.

I also think there is value in having these paper wallets with you and when you want to buy something with your mobile phone you load the private key with your mobile. That way you don't have to leave too much BTC on your phone or with an online wallet where it can be hacked.

[dentldir]

I think the question is "how do I know the private key that I can't see actually unlocks the address on the bill?"  This is exactly the problem with any physical bitcoins you can make at home - the person receiving them has to trust that there's not just a happy face under the hologram instead of a privkey.

This.  In reading the wiki:

https://en.bitcoin.it/wiki/Private_key

It says that the private key and the address are mapped one to one.  So the verification would be the same as the "Generate Address" function in the client just using a precreated private key.  I supposed I answered my own question:  Verifying a private key offline is trivial and does not require access to the blockchain to do so.

Cool.

[SgtSpike]

I think the question is "how do I know the private key that I can't see actually unlocks the address on the bill?"  This is exactly the problem with any physical bitcoins you can make at home - the person receiving them has to trust that there's not just a happy face under the hologram instead of a privkey.

This.  In reading the wiki:

https://en.bitcoin.it/wiki/Private_key

It says that the private key and the address are mapped one to one.  So the verification would be the same as the "Generate Address" function in the client just using a precreated private key.  I supposed I answered my own question:  Verifying a private key offline is trivial and does not require access to the blockchain to do so.

Cool.

But, verifying that coins do indeed exist at the corresponding public key DOES require access to the blockchain (or a trusted service).

[pointbiz]

I think the question is "how do I know the private key that I can't see actually unlocks the address on the bill?"  This is exactly the problem with any physical bitcoins you can make at home - the person receiving them has to trust that there's not just a happy face under the hologram instead of a privkey.

This.  In reading the wiki:

https://en.bitcoin.it/wiki/Private_key

It says that the private key and the address are mapped one to one.  So the verification would be the same as the "Generate Address" function in the client just using a precreated private key.  I supposed I answered my own question:  Verifying a private key offline is trivial and does not require access to the blockchain to do so.

Cool.

This verification can be done with bitaddress.org on the Wallet Details tab.

[unclemantis]

How would one verify an offline wallet, OFFLINE?

[Gyrsur]

How would one verify an offline wallet, OFFLINE?

not possible, the receiver has to check it online before accepting the bill and transfer the amount away. one possibility could be a trusted third party check the oflline wallet during print out of the bill but then the problem is after print out someone can use the private key and transfer the amount away. a quick check would be to check if the public adress was used already in the past. if not the bill has the whole amount. EDIT: nonsense, offline wallet has to be loaded therefore it was used already!

[unclemantis]

How would one verify an offline wallet, OFFLINE?

not possible, the receiver has to check it online before accepting the bill and transfer the amount away. one possibility could be a trusted third party check the oflline wallet during print out of the bill but then the problem is after print out someone can use the private key and transfer the amount away. a quick check would be to check if the public adress was used already in the past. if not the bill has the whole amount. EDIT: nonsense, offline wallet has to be loaded therefore it was used already!

The selling point of paper money or coin money is that the value of the token is already established and knowledge that once the token exchanges owners the value of it transfers as well as 100 percent of the control. I do not think that having bitcoin paper money is going to act 100 percent like the precived notion of existing paper or metal monetary tokens.

My thoughts are that we need to revisit the intended use of the paper wallet for everyday transactions.

Thoughts?

[cbeast]

How would one verify an offline wallet, OFFLINE?

not possible, the receiver has to check it online before accepting the bill and transfer the amount away. one possibility could be a trusted third party check the oflline wallet during print out of the bill but then the problem is after print out someone can use the private key and transfer the amount away. a quick check would be to check if the public adress was used already in the past. if not the bill has the whole amount. EDIT: nonsense, offline wallet has to be loaded therefore it was used already!

The selling point of paper money or coin money is that the value of the token is already established and knowledge that once the token exchanges owners the value of it transfers as well as 100 percent of the control. I do not think that having bitcoin paper money is going to act 100 percent like the precived notion of existing paper or metal monetary tokens.

My thoughts are that we need to revisit the intended use of the paper wallet for everyday transactions.

Thoughts?

They are not intended to be used for transactions except maybe under special circumstance. They are nice looking offline wallets.

[Gyrsur]

How would one verify an offline wallet, OFFLINE?

not possible, the receiver has to check it online before accepting the bill and transfer the amount away. one possibility could be a trusted third party check the oflline wallet during print out of the bill but then the problem is after print out someone can use the private key and transfer the amount away. a quick check would be to check if the public adress was used already in the past. if not the bill has the whole amount. EDIT: nonsense, offline wallet has to be loaded therefore it was used already!

The selling point of paper money or coin money is that the value of the token is already established and knowledge that once the token exchanges owners the value of it transfers as well as 100 percent of the control. I do not think that having bitcoin paper money is going to act 100 percent like the precived notion of existing paper or metal monetary tokens.

My thoughts are that we need to revisit the intended use of the paper wallet for everyday transactions.

Thoughts?

Bitcoin 2.0 ??
there has to be exist special private keys only for offline wallets. only two transactions are allowed for them. 1. fund it 2. clear it

EDIT: in addition a trusted website check the public key if the offline wallet is funded and print out the bill and seal the bill with "amount approved by bla bla" ore something like that, but the receiver has to check it also if funded, so it is senseless

EDIT2: we need private keys where transactions are not allowed, then you can create a private key with a certain amount. for this you need a authority which you allowed to get a private key with a certain amount and to put a private keys amount to a private key allowed for transactions. but this could be tricky with no authorities!

EDIT3: there may be a need for a trusted third party which prints bills for bitcoins. you send this party your amount via transaction. they print the bill with a private key which is not allowed for transactions and send the bill to you. if you want to convert "papercoins" into bitcoins you have to send the bills to the trusted third party and they will send you the amount via transaction. divide and rule

--end--

[rebuilder]

EDIT3: there may be a need for a trusted third party which prints bills for bitcoins. you send this party your amount via transaction. they print the bill with a private key which is not allowed for transactions and send the bill to you. if you want to convert "papercoins" into bitcoins you have to send the bills to the trusted third party and they will send you the amount via transaction. divide and rule

--end--

Like an exchange? It's a little more complicated than you outline, but I take my paper money to this place called "a bank", they convert the paper into bits for me, which I wire over to an exchange of my choice and they let me convert it to BTC. The process works in reverse too, converting Bitcoins to third party paper money.

[Gyrsur]

EDIT3: there may be a need for a trusted third party which prints bills for bitcoins. you send this party your amount via transaction. they print the bill with a private key which is not allowed for transactions and send the bill to you. if you want to convert "papercoins" into bitcoins you have to send the bills to the trusted third party and they will send you the amount via transaction. divide and rule

--end--

Like an exchange? It's a little more complicated than you outline, but I take my paper money to this place called "a bank", they convert the paper into bits for me, which I wire over to an exchange of my choice and they let me convert it to BTC. The process works in reverse too, converting Bitcoins to third party paper money.

yeah, but Bitcoin paper money with change rate 1:1, maybe a second blockchain only for "Papercoins" and merge mined like Namecoins

EDIT: the problem with bitcoin bills are the transactions, for bitcoin bills you don't need transactions, it is offline money like cash

[unclemantis]

Is there a way to create a key that is visible and when combined with another key of sorts creates a valid private key? You know like on checks the amount is of money that is transferred from the account number on the bottom is only valid by so and so?

Thoughts?

[adamstgBit]

Windows users can download my current version of the utility and print Bitcoin notes!

link?

Earlier in thread, should be:

https://casascius.com/btcaddress.zip

thanks

i dont see how to print out the bill

i see how to print out a list of paper wallets

[casascius]

I just posted an update to my Bitcoin Address Utility that allows you to create and decrypt password-protected private keys.  The keys are roughly the same size as normal private keys, but they start with "6p".

The utility can now print paper wallets with AES-encrypted keys.

This has barely been tested, so don't use it with any serious amount of money (or, use a deterministic wallet so you can recover it unencrypted).

https://casascius.com/btcaddress.zip

[dentldir]

But, verifying that coins do indeed exist at the corresponding public key DOES require access to the blockchain (or a trusted service).

Correct.

So when using these bills in transactions you have to have access to the block chain.  And any transaction has to start with verifying the funds are there and immediately transferring the funds to another address.  Offline confirmation can only tell you that the private key belongs to the address, which could have nothing in it.  

A scammer would have to create some kind of race condition at the same time you do your verify and move to try and get the money before you do.  (i.e. trigger an automated transfer of their own right before you do yours).  So if they are pounding away on their cell phone as you are scanning the QR codes with your phone you know something is up.  Although the trigger person could be a block away with binoculars waiting for some kind of signal as well.  I'm sensing the plot to a really bad movie here but its fun to think about nonetheless.

Another angle on this is that paper makes a better archival medium than DVD-R or USB keys.  So print up a BTC note, fund it, then  deposit it in a safety deposit box.

[dentldir]

This verification can be done with bitaddress.org on the Wallet Details tab.

I did see that. Reading the Javascript there is exactly how I got my head straight on this stuff.

That page is amazing.  If anyone hasn't read the source, do yourself a favor and check it out.

[dentldir]

I just posted an update to my Bitcoin Address Utility that allows you to create and decrypt password-protected private keys.  The keys are roughly the same size as normal private keys, but they start with "6p".

The utility can now print paper wallets with AES-encrypted keys.

This has barely been tested, so don't use it with any serious amount of money (or, use a deterministic wallet so you can recover it unencrypted).

https://casascius.com/btcaddress.zip

Thanks so much for sharing this.  Downloading now.

[pointbiz]

How would one verify an offline wallet, OFFLINE?

You can verify that the Bitcoin address corresponds to the private key if you have a smart phone with qr code scanner and a saved version of bitaddress.org (you can download the zip from github).

As for the balance you need data from the block chain.

[Gyrsur]

epic epic stuff:)

could be!  

really, i see a need for a second blockchain for bitcoin bills. an "authority" has to observe the transfer from bitcoins to "papercoins" and back somehow. the "authority" can also be distributed. the money supply has to match against each other between the two blockchains. at the moment "papercoins" would be behind with money supply but this doesn't matter because the need for "papercoins" is low but could be raised in the future. exchange rate is 1:1. if you "transfer" bitcoins into "papercoins" the bitcoin amount would be frozen like a lost wallet. the amount is now on the "paperbill". you can change it with trust together with other parties. if you want to transfer the amount online you have to change back "papercoins" into bitcoins 1:1. then the amount of money is available in the bitcoin network and the bill is destroyed. very similar like central banks deal with cash.

[cbeast]

epic epic stuff:)

could be!  

really, i see a need for a second blockchain for bitcoin bills. an "authority" has to observe the transfer from bitcoins to "papercoins" and back somehow. the "authority" can also be distributed. the money supply has to match against each other between the two blockchains. at the moment "papercoins" would be behind with money supply but this doesn't matter because the need for "papercoins" is low but could be raised in the future. exchange rate is 1:1. if you "transfer" bitcoins into "papercoins" the bitcoin amount would be frozen like a lost wallet. the amount is now on the "paperbill". you can change it with trust together with other parties. if you want to transfer the amount online you have to change back "papercoins" into bitcoins 1:1. then the amount of money is available in the bitcoin network and the bill is destroyed. very similar like central banks deal with cash.

"Papercoins" as you put it are traded purely by trust unless you use a Bitcoin Checkbook which is treated like any bitcoin transaction.

[Gyrsur]

epic epic stuff:)

could be!  

really, i see a need for a second blockchain for bitcoin bills. an "authority" has to observe the transfer from bitcoins to "papercoins" and back somehow. the "authority" can also be distributed. the money supply has to match against each other between the two blockchains. at the moment "papercoins" would be behind with money supply but this doesn't matter because the need for "papercoins" is low but could be raised in the future. exchange rate is 1:1. if you "transfer" bitcoins into "papercoins" the bitcoin amount would be frozen like a lost wallet. the amount is now on the "paperbill". you can change it with trust together with other parties. if you want to transfer the amount online you have to change back "papercoins" into bitcoins 1:1. then the amount of money is available in the bitcoin network and the bill is destroyed. very similar like central banks deal with cash.

"Papercoins" as you put it are traded purely by trust unless you use a Bitcoin Checkbook which is treated like any bitcoin transaction.

goal should be to manage bitcoin bills completely offline until you will transfer the amount via bitcoin network. there should be no need for a receiver of bitcoin bills to convert it to bitcoins until he will transfer the amount to anywhere online. concept of Bitcoin Checkbook has the need to check the loaded amount online to trust into it.

EDIT: reason for the need to be completely offline for a while could be a natural disaster, a war or something other where an online access is not possible. in this case you can take your bitcoin bills with you at least.

EDIT2: intention is to fit this requirement

How would one verify an offline wallet, OFFLINE?

[PrintCoins]

Just created a web based way to print these bills as well as printcoin bills.

Take a look at it here:

http://tinyurl.com/bitbill  (pdf link)

Note: Do not use this set of bills generated by this url. They are using private keys that will be available to all.
 
Go to http://print.printcoins.com to generate your own.

[jago25_98]

So to scan it you'd need a mobile phone, what's the benefit of having paper at all then? I'm trying to think of uses for this and it seems there's very limited and specific scenarios it'd be useful.

I guess because people might finally get it

[Tril]

EDIT3: there may be a need for a trusted third party which prints bills for bitcoins. you send this party your amount via transaction. they print the bill with a private key which is not allowed for transactions and send the bill to you. if you want to convert "papercoins" into bitcoins you have to send the bills to the trusted third party and they will send you the amount via transaction. divide and rule

--end--

Like an exchange? It's a little more complicated than you outline, but I take my paper money to this place called "a bank", they convert the paper into bits for me, which I wire over to an exchange of my choice and they let me convert it to BTC. The process works in reverse too, converting Bitcoins to third party paper money.

If you need a trusted third party, Open-Transactions already has the protocol and implementation for what you're discussing in one of its modes.  See this link to decide which mode.  The O-T server is the trusted third party or bank. It's not the same as bitcoin, but you can issue new currencies and trade bitcoins for them.  You can certainly print it on paper.

https://github.com/FellowTraveler/Open-Transactions/wiki/Instruments

videos thread-  https://bitcointalk.org/index.php?topic=93086.0

[Gyrsur]

EDIT3: there may be a need for a trusted third party which prints bills for bitcoins. you send this party your amount via transaction. they print the bill with a private key which is not allowed for transactions and send the bill to you. if you want to convert "papercoins" into bitcoins you have to send the bills to the trusted third party and they will send you the amount via transaction. divide and rule

--end--

Like an exchange? It's a little more complicated than you outline, but I take my paper money to this place called "a bank", they convert the paper into bits for me, which I wire over to an exchange of my choice and they let me convert it to BTC. The process works in reverse too, converting Bitcoins to third party paper money.

If you need a trusted third party, Open-Transactions already has the protocol and implementation for what you're discussing in one of its modes.  See this link to decide which mode.  The O-T server is the trusted third party or bank. It's not the same as bitcoin, but you can issue new currencies and trade bitcoins for them.  You can certainly print it on paper.

https://github.com/FellowTraveler/Open-Transactions/wiki/Instruments

videos thread-  https://bitcointalk.org/index.php?topic=93086.0

very interesting! thanks!