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

[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.

[1714976473]

1714976473

[1714976473]

1714976473

[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...