How would you like to design a bitcoin banknote?

[Red Emerald]

It seems to me that a would-be scammer could slice off the cap with an X-Acto knife or a razor blade, scan the QR code, and carefully apply a second layer of tape. Subsequent recipients of the note probably wouldn't notice until it was too late.

A last resort for tamper proofing is to apply the lottery scratch card method of rubbery sealing over the private key. But then the note might have to be in plastic?. It for sure will get a very ugly rubbery blob, in place of a beautiful BTC marked hologram  .

I can´t imagine high tech is needed to apply the rubber (?) covering over the private key, and it can´t cost much as it is already in widespread use for cheap lottery tickets.

And how do you prove to the person you are paying that there is actually a private key underneath the rubber?

[Ignore@YourPeril]

I don´t have anything more to offer than what people do today on a regular basis with ordinary government issued cash: they trust their ability to be able to notice a counterfeit note from eyesight inspection, by some hologram or intricate artwork printing which both identifies the issuer and makes counterfeiting of the visible parts hard to do.

If this trust is not misplaced, the only way for having no private key underneath is that the issuer is scamming the public - which rather would be done by simply making in all parts identical copies of notes, including the private key. And if this issuer is living nearby, you will know where to find her...

[franky1]

The less centralized solution, more in the spirit of bitcoin, is to sell only the hologram. This should contain something like the PGP signed email address of anyone wanting to start issuing their own notes. Still a chain of trust, but a short one: casascius has to be trusted only to sell his customized hologram stickers to the owner of the email address. After that the one remaining link is to trust the local issuer, identified by this very email address.

thats a better idea, where each person had a hologram. it does not have to even be a PGP key for businesses selling the notes, for example:
http://donttreadonmeme.com/what-is-a-bitcoin-bank-note/
they could have the snake image as their hologram making it instantly recognisable as to its origin.

so anyone that is going to make notes for circulation purposes should have their own design hologram. and if your just an individual then a pgp key or your bitcointalk name on the hologram may suffice.

[casascius]

so anyone that is going to make notes for circulation purposes should have their own design hologram. and if your just an individual then a pgp key or your bitcointalk name on the hologram may suffice.

It's just so much easier to make coins than notes!

[ercolinux]

There are holograms numbered, putting one of them over the private key and print the same number on the bill reduce a lot the risk of counterfeit. But still to accept a self printed bill you've to trust the emitter and the person who gives it to you. I think that the bills are nice idea as introduction to bitcoins, or to store some bitcoins but a wide use of them is not simple, unless you use a central emitter of bitbils (but this is in contrast with the idea of bitcoin).

[Tacticat]

Yes it is, centralized manufacturing of the hologram is a practical and economical way of identifying the issuer of the notes - and making them hard to forge also.

It will be nothing like a central bitcoin bank issuing all notes, which opens the possibility for all notes being redeemed by a scammer holding all private keys. The possibility for this happening with distributed issuing will have only local impact, and will be far less likely to happen.

A CENTRALIZED manufacturer is a problem.

IMO, for paper bills to work and remain in circulation, there has to be a 100% way for any party to validate that their bill is secure.  The bills presented here can only be fully trusted if you are part of the manufacturing process.

Bitcoin is impossible to counterfeit. The proposed bills are possible to counterfeit.  Any solution where counterfeiting could be a problem is a non-starter for me.

If not from a centralized trustworthy manufacturer, how can you be certain that the private key is vaild?

How can you know that there is actually a private key under the hologram if everybody can issue out bitnotes?

[casascius]

You kind of can't, but fortunately it is so expensive to get your own hologram that few are going to do it frivolously and without putting their name on them. Anonymous holograms are cheap there is no point in making a custom no name design.

[Stephen Gornick]

You kind of can't, but fortunately it is so expensive to get your own hologram that few are going to do it frivolously and without putting their name on them. Anonymous holograms are cheap there is no point in making a custom no name design.

Well, looks like bitcoin is no longer the only pioneer here.

"You can send a Square gift card to anyone with an email address. No smartphone? They can print out a QR code."

That's Square's Jack Dorsey:
 - https://twitter.com/jack/status/277824833130209280

I haven't seen a printout from Square with one of these gift cards, I'ld be curious to see one though.  (e.g., what size is the QR code).

But this paper QR code as a bearer instrument works because it is familiar -- it works kind of like cash [Edit: as long as the underlying electronic transaction can occur.]

[Richy_T]

You kind of can't, but fortunately it is so expensive to get your own hologram that few are going to do it frivolously and without putting their name on them. Anonymous holograms are cheap there is no point in making a custom no name design.

Well, looks like bitcoin is no longer the only pioneer here.

"You can send a Square gift card to anyone with an email address. No smartphone? They can print out a QR code."

That's Square's Jack Dorsey:
 - https://twitter.com/jack/status/277824833130209280

I haven't seen a printout from Square with one of these gift cards, I'ld be curious to see one though.  (e.g., what size is the QR code).

But this paper QR code as a bearer instrument works because it is familiar -- it works kind of like cash [Edit: as long as the underlying electronic transaction can occur.]

Bear in mind that it's a gift card. If you wanted to try and complete a transaction with it, you'd run into similar trust issues. Gift card fraud is rife and you'd be foolish to trust it on its own merits.

Since I'm posting anyway, I'll just add that I think the whole bitcoin-note thing is a bit ill advised. It's trying to be something that it isn't and can't be. Even Casascius' coins (which are cool) are somewhat marginal really. Though with that said, I don't want to rain on anyone's parade so I'll be pleasantly surprised if this works out well.

[Stephen Gornick]

It's trying to be something that it isn't and can't be.

And I'm on the opposite end of the spectrum.  Single-use paper Bitcoins are even better than paper currency.   The QR code is scanned and and the document discarded.   Either there were funds from it or there weren't.   For the change I get my local currency and coin, just as if I had paid cash.   Or I can show the public ("load & verify") QR code for my the next one and get a receipt from the merchant showing the address and the transaction id.

[Red Emerald]

It's trying to be something that it isn't and can't be.

And I'm on the opposite end of the spectrum.  Single-use paper Bitcoins are even better than paper currency.   The QR code is scanned and and the document discarded.   Either there were funds from it or there weren't.   For the change I get my local currency and coin, just as if I had paid cash.   Or I can show the public ("load & verify") QR code for my the next one and get a receipt from the merchant showing the address and the transaction id.

I think Richy is talking about trying to make bills that stay in circulation.  Single-use notes work great.

[Ignore@YourPeril]

I think Richy is talking about trying to make bills that stay in circulation.  Single-use notes work great.

Michael_S has presented a practical solution for making single use notes safely on a PC, with QR codes and all. This thread, and other threads around here,  abounds with beautiful artwork for notes. The two steps away from this to distributed (as in anyone owning a PC and some bit coins) issuing of bills for circulation are: 1. tamper proofing of what´s hiding the private key, and 2. measures to prevent counterfeiting of the visible parts of the note.

1. A solution already exists in that of scratch card lottery tickets, and I can´t imagine applying a rubber coating on plastic will require a lot of investment in equipment.

2. This is likely to be the most tricky part for an economical distributed solution, so I will assume a partial centralization is required. Like that of small banks getting their token credit cards from a central manufacturer, for then stamping the cards themselves with an account number and so on ( I assume this is the way it is done. This central producer of blank bitcoin notes will be able to counterfeit, but this event will not effect the holders of genuine bills (as they can be redeemed to online BTC)

And maybe there is a point 3. Preparing for lawsuits after the government gets wind of it...  

[casascius]

All of these solutions sound so difficult.

One could also do a coin.  A coin is so freaking easy.  You put a sticker on it very carefully.  Voila!  It lasts much longer than any piece of paper.

Anyone who wants to put $5000 into their own coins and holograms can start making coins just like I do.  I see little reason why someone should want to create a hardened bill meant for circulation but then design it so it scratches off like a lottery ticket and therefore doesn't last.  Casascius Coins will survive a trip through the wash.  If the sticker were lacquered over with something that hardened well, the coins would be almost as resilient as any other coin.

I have thought of lottery tickets, but would think of them mostly as a way to mass-produce disposable wallets.  If I can get BIP 38 to get a little bit more widespread adoption, then having scratchoff disposable paper wallets made by a lottery ticket company would actually be very realistic.  Independent party A could pre-generate intermediate codes for random passphrases and put them in a file.  Independent party B could create the actual product through a company that prints lottery tickets, using those intermediate codes.  Party A takes the final product and somehow overprints the per-ticket passphrase on the outside.  Nobody in the supply chain ever gets access to the real private keys, since redeeming any piece requires both the passphrase and the junk under the scratchoff.

[Ignore@YourPeril]

If the initial investment for making physical coins is as low as you indicate, then coining might well be the best option for distributed issuing. I was just  thinking of a natural progression from the notes of this thread. If coins are easier to make resistant to counterfeiting, then that´s a good argument to  choose coins to circulate bitcoins. Yours are really cool, btw!

Then I will also brave the danger of scorn from those abhorrent of centralizing to make another suggestion: If coins are to be used for distributed issuing then a uniform design of the front side (opposed to the hologram) sounds like a practical idea? Any "empty" coin redeemed could then be re-coined easily by another distributed issuer. Bitcoin foundation, anyone?

[fivemileshigh]

This is a personal request for Mr. Salfter if I may, and assuming it's not too much trouble:

Could we have a bitcoin bill background image with the golden bitcoin circle on light blue, light green and light purple backgrounds? I think it would look realy cool.

So, the gold "B" circle from the grey one:



added to these ones:







I would like to use the png with Michael S's modified bitaddress utility.

Many thanks in advance! If not possible, no worries

[casascius]

If the initial investment for making physical coins is as low as you indicate, then coining might well be the best option for distributed issuing. I was just  thinking of a natural progression from the notes of this thread. If coins are easier to make resistant to counterfeiting, then that´s a good argument to  choose coins to circulate bitcoins. Yours are really cool, btw!

Then I will also brave the danger of scorn from those abhorrent of centralizing to make another suggestion: If coins are to be used for distributed issuing then a uniform design of the front side (opposed to the hologram) sounds like a practical idea? Any "empty" coin redeemed could then be re-coined easily by another distributed issuer. Bitcoin foundation, anyone?

Actually, I deliberately designed my 1 BTC coin to be generic enough that others could use it.  It does not say Casascius on it, even though it could.  The only coins I make where I put Casascius on the metal itself are the silver and gold (Casascius is embedded in the binary on the back of the silver, and on the front of the gold).

If someone wants to run coins and would like to discuss what a new 2013 coin should look like, perhaps we can split the cost of the dies and get better pricing on a combined order.  You would need about a $2000-$2500 minimum budget just for coin blanks.

[salfter]

Could we have a bitcoin bill background image with the golden bitcoin circle on light blue, light green and light purple backgrounds? I think it would look realy cool.

That should be doable...just need to see what color was left alone in the existing grayscale note and change the others accordingly.  I'll post again when I have them ready.

[LoweryCBS]

Like this?:

Could we have a bitcoin bill background image with the golden bitcoin circle on light blue, light green and light purple backgrounds? I think it would look realy cool.

That should be doable...just need to see what color was left alone in the existing grayscale note and change the others accordingly.  I'll post again when I have them ready.

[salfter]

Could we have a bitcoin bill background image with the golden bitcoin circle on light blue, light green and light purple backgrounds? I think it would look realy cool.

That should be doable...just need to see what color was left alone in the existing grayscale note and change the others accordingly.  I'll post again when I have them ready.

...and they're up:

https://www.dropbox.com/sh/ubt85fo4qx57s0h/m4f9Yapgt3/btcnotes

SVG, EPS, and PNG (rendered at 600 dpi) are available.

[fivemileshigh]

They're absolutely beautiful, thank you so much! tip sent

I'm thinking, besides handing out quarter bitcoin notes to people, I'd like to keep a larger note in my wallet, like say a 50btc. The idea is to hopefully spark the idea in people's minds that bitcoin isn't just "play" money. A 50 btc bill is 500 euros, if people can "get" emotionally that this is as real as it gets, that would be a big step forward. The drawback is I wouldn't normally carry a 500 euro bill in my wallet though, so I'm a little ambivalent about the idea. This is one case where I'd definitely keep a copy of the private key at home.



Edit: I just noticed, you edited the slightly more saturated ones, I was hoping to use the more subdued colors, see example below:





Any chance you could add the gold B to the more subdued ones please? thanks