A "real" Bitcoin

[tcatm]

That coin is a very cool momento. You should consider selling that merchandise.

I'm working on it. I'm currently trying to make a copper core + gold surface coin.

[1714866696]

1714866696

[nanotube]

100925 blocks. 75 blocks until auction end.

[Luke-Jr]

That coin is a very cool momento. You should consider selling that merchandise.

Real bitcoin currency though would just be hard-to-manufacture paper notes with a barcode that has an address with 1 BTC in.

So transfer that BTC to your own address, and pass the paper on? Nah, you need some kind of scratch-off to show it's used

[grondilu]

IMO, you're taking this way too seriously guys.

A physical bitcoin is cool, but it's nothing but symbolic.  There is obviously no way to have any physical object store a bitcoin.  Otherwise we wouldn't need bitcoin in the first place.  A physical object can be counterfaited, and if you plan on putting ECDSA keys in it, it can be copied.  And you still have the double spending problem.  And I'm sure there are many other reason why a physical bitcoin can be nothing but some kind of a marketing toy or something alike.

Still, I'd like to have one.  Especially if it's solid gold.

[casascius]

IMO, you're taking this way too seriously guys.

A physical bitcoin is cool, but it's nothing but symbolic.  There is obviously no way to have any physical object store a bitcoin.  Otherwise we wouldn't need bitcoin in the first place.  A physical object can be counterfaited, and if you plan on putting ECDSA keys in it, it can be copied.  And you still have the double spending problem.  And I'm sure there are many other reason why a physical bitcoin can be nothing but some kind of a marketing toy or something alike.

Still, I'd like to have one.  Especially if it's solid gold.

I assert that a smart card is a physical object that can securely store a bitcoin.

A smart card is an integrated circuit that, among other things, can store a private key and sign things with it without divulging the private key.  A smart card can also enforce pre-programmed constraints by itself.  Many smart cards can generate public/private key pairs on-chip, and encrypt/decrypt data streams in real time.

[grondilu]

I assert that a smart card is a physical object that can securely store a bitcoin.

A smart card is an integrated circuit that, among other things, can store a private key and sign things with it without divulging the private key.  A smart card can also enforce pre-programmed constraints by itself.  Many smart cards can generate public/private key pairs on-chip, and encrypt/decrypt data streams in real time.

Yeah but to pay with a smartcard, you don't give the smartcard !  It's a completely dofferent purpose than a monetary token.

[casascius]

Yeah but to pay with a smartcard, you don't give the smartcard !  It's a completely dofferent purpose than a monetary token.

Why not?  A smart card can be given away just like any other tangible object.

[grondilu]

Why not?  A smart card can be given away just like any other tangible object.

Am I missing something or what ?  If you give the smartcard, the only way for the receiver to check that it realy has some value is to proceed to a transfer.  Then the card doesn't have any value anymore.  So what's the point of keeping it ?

[casascius]

Why not?  A smart card can be given away just like any other tangible object.

Am I missing something or what ?  If you give the smartcard, the only way for the receiver to check that it realy has some value is to proceed to a transfer.  Then the card doesn't have any value anymore.  So what's the point of keeping it ?

If the smart card had a custom application that simply proved that it contained the private key associated with some real Bitcoins out there, the value could be checked simply by confirming that the corresponding Bitcoin address had a balance.

If the Bitcoin system allowed bitcoins to be encumbered by TWO private keys instead of one, and the second one were settable by any user in possession of the card (a change would be announced to the blockchain so it would be enforced by all nodes), it would eliminate the risk that someone who secretly acquired the private key within the card (e.g. the manufacturer) could spend the coins after he had given away the card.

[grondilu]

If the smart card had a custom application that simply proved that it contained the private key associated with some real Bitcoins out there, the value could be checked simply by confirming that the corresponding Bitcoin address had a balance.

If the Bitcoin system allowed bitcoins to be encumbered by TWO private keys instead of one, and the second one were settable by any user in possession of the card (a change would be announced to the blockchain so it would be enforced by all nodes), it would eliminate the risk that someone who secretly acquired the private key within the card (e.g. the manufacturer) could spend the coins after he had given away the card.

It seems to be quite complicated but I guess it's possible.

I don't think it would harm the bitcoin network anyway, so go for it.

[casascius]

It seems to be quite complicated but I guess it's possible.

I don't think it would harm the bitcoin network anyway, so go for it.

Here's some context:

http://img810.imageshack.us/i/photoph.jpg/

These credit card machines are nothing more than simple desktop computers with a POSIX-like proprietary OS that can be written to in C / C++.  This is a "proof of concept" video poker application I wrote for the VeriFone Vx series credit card machines.

Each of these machines has a smart card reader, and the API allows the sending and receiving of arbitrary commands to the smart card... a smart card with custom application can handle these however it has been programmed.

edited to add: the real obstacle is that it would be necessary for Bitcoin to allow bitcoins to be encumbered by a second private key.  Otherwise all kinds of attacks are trivial.  Someone suggested this was already possible - I'm afraid I don't understand the workings of the Bitcoin protocol well enough at this point to say whether or not that was so.

[Pegasus-Rider]

I would like to see a traditional coin representing BTC, and I see it as follows:
It would be made of a valuable metal or alloy (Germanium-Titanium sounds extremely attractive, particularly because of its bit-significance), with Bitcoin symbols and guarantee to exchange such tokens for bitcoins, effectively making these representative money with a meaningful value of their own.
For minting we may refer to Wirtland project experience and perhaps even propose bitcoin as their currency on this occasion.
How does it sound?

[Vinnie]

If and when BTC becomes more widely accepted, I'd consider starting a physical currency that is pegged to bitcoins.

[jgarzik]

Am I missing something or what ?  If you give the smartcard, the only way for the receiver to check that it realy has some value is to proceed to a transfer.  Then the card doesn't have any value anymore.  So what's the point of keeping it ?

A physical-world digital store of money has many uses.  Anonymous, reloadable VISA debit cards are quite popular, for example.  A card would be nothing more than an anonymous bitcoin wallet.

Currently bitcoins are as portable as your computer...  but they could be more portable with a smartcard.

Simply handing someone a card is a useful way to move money.

[Pegasus-Rider]

If and when BTC becomes more widely accepted

It might be this very initiative that will help to popularise Bitcoin - you know, a /. post about it, news site articles and so on.

[Vinnie]

If and when BTC becomes more widely accepted

It might be this very initiative that will help to popularise Bitcoin - you know, a /. post about it, news site articles and so on.

True. What do you think; paper bills or coins?

[ribuck]

If and when BTC becomes more widely accepted, I'd consider starting a physical currency that is pegged to bitcoins.

Fractional reserve banking, in other words. I'm not criticizing though. It's inevitable, and it's harmless provided the level of backing behind the "pegging" is honestly disclosed.

[Vinnie]

Fractional reserve banking, in other words. I'm not criticizing though. It's inevitable, and it's harmless provided the level of backing behind the "pegging" is honestly disclosed.

I suppose you could call it that. I envision an issuer as making the market for the currency, rather than accepting deposits and issuing bearer certificates. Perhaps its just semantics, but in making the market for a pegged currency for an honest, razor thin spread, an issuer would demonstrate a consistent commitment to maintain its trade value at face value.

[em3rgentOrdr]

This whole discussion reminds me of the "Printing Bitcoins : Could it Work?" discussion.

It'd be cool to come up with a coin design that's RepRappable. It'd fit well with the decentralized philosophy of BitCoin :-)

http://reprap.org/

For making it an actual coin that's useful for transactions, you could embed an NFC chip into it. The tag chips cost about a dollar, I think, and can store small amounts of arbitrary data that can then be read by near field radio. It'd probably be possible to fit a keypair into it.

I like that idea.  Where can I buy a NFC chip today for a dollar?

IMO, you're taking this way too seriously guys.

A physical bitcoin is cool, but it's nothing but symbolic.  There is obviously no way to have any physical object store a bitcoin.  Otherwise we wouldn't need bitcoin in the first place.  A physical object can be counterfaited, and if you plan on putting ECDSA keys in it, it can be copied.  And you still have the double spending problem.  And I'm sure there are many other reason why a physical bitcoin can be nothing but some kind of a marketing toy or something alike.

Still, I'd like to have one.  Especially if it's solid gold.

I like the idea of backing gold with something of real value, like bitcoin.  Heck, fundamentally, gold is currently "backed by nothing!" (deliberate scare quotes)  

I assert that a smart card is a physical object that can securely store a bitcoin.

A smart card is an integrated circuit that, among other things, can store a private key and sign things with it without divulging the private key.  A smart card can also enforce pre-programmed constraints by itself.  Many smart cards can generate public/private key pairs on-chip, and encrypt/decrypt data streams in real time.

EXACTLY!  Excellent idea.  Just embed this bitcoin smart card chip with NFC inside of a plastic rep-rap or makerbot plastic 'coin' and you have a "real" bitcoin!

However, is there a way that you can verify the bitcoin wallet that you embed inside this smart card chip has NO OTHER COPIES?  Potentially, couldn't the manufacturer or distributor of these bitcoin smart cards keep a backup of the wallet at their company headquarters when they first create the bitcoin smart card?  I guess maybe you can't trust a pre-loaded bitcoin smart card, and instead can only trust bitcoin smartcards that you generate a new address inside it yourself which gets sent a bitcoin.

[Vic]

For minting we may refer to Wirtland project experience and perhaps even propose bitcoin as their currency on this occasion.
How does it sound?

Wirtland would be glad to collaborate, I guess. (By the way, our next physical coin will be with Julian Assange portrait, see http://www.tiny.lu/o27px!)  But I have to agree that a smart card, such as an anonymous VISA, would be much better for practical use. In fact, Wirtland has been discussing this for a long time. Wirtland issues plastic IDs, and wants to have them serve for payments - by inserting chip, magnetic band or other technology.