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

[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.