Bitcoin Forum

The card will behave as follows:
1. It is very secure, more so than even a paper wallet in some ways.
2. It holds Bitcoin and pays Bitcoin, no MasterCard/VISA etc. involved.
3. Anyone with a PC or an Android phone could accept this BTC credit card (globally).
4. You can pay no fee if you want or easily program your own card if you don't trust providers.
5. Is open source.
6. It would cost 6-20$ with the price dropping every year as with all electronics.

Would you buy this?

I would like to see a multipurpose card with a chip for Bitcoin and a strip for fiat.

I've bought two full sets of BitBills (http://BitBills.com), Casascius coins, and a lovebitcoins.org Bitcoin gift card (https://bitcointalk.org/index.php?topic=73978.0).

Is it pure Bitcoin or is it mixed in with other currencies?

If you mean litecoin and such you could conceivably add support for those too.

USD, EUR, Yuan and such; no.

That might be pretty neat.

Is this coming out of your previous work using the ZC5.4 card (https://bitcointalk.org/index.php?topic=7539.140)?

Otherwise, where does it fit into the existing Hardware wallets (https://bitcointalk.org/index.php?topic=134277.0) that are in progress?

I'd think there would be a market for cards that don't have a screen or keypad to know what you are paying for, but they would necessarily be limited to small amounts of BTC. The biggest problem would be trusting a hacked payment terminal or host not to just steal all the funds from the card.

Hell yea I would

It is still the ZC5.4.

However I developed a payment process that does not require trust in the terminal (its in the thread somewhere):

The card will multiply the requested amount with a number only you know and then you only give the PIN if this number fits. The terminal cannot fake-double-charge either as the card will lock itself for while after each transaction.


You can still trick this system, but it requires quite some effort and the card holder could immediately know who ripped him off and can call the cops.
Further safe guards are possible like self-incrementing PIN codes or maximum withdrawals.
Even if somehow overcharged the keys never leave the card so it cannot get compromised the way a VISA card can.


The paper wallet thing; if you just keep the card in a safe and only use it with your own phone/PC to withdraw once in a great while it becomes safer than paper since paper doesn't require a code to read (except for encrypted paper wallets).

this type of card would have to offer more security than a smartphone based wallet like Bitcoin Spinner in order to add value.

from the sounds of what you've described this appears to be the case.  so, yes.

No doubt there will be a Bitcoin card within the coming 1-2 years, which will boost the Bitcoin prices, Buy, Buy, Buy!!!!

Could you describe the price multiplication security in more detail?

Is this the way it would work:

• The terminal requests a 2 bitcoin charge
• The secret multiplication number is 42
• The card returns 84
• The terminal displays 84 to the customer.
• The customer verifies that 84 is <the requested change> * 42 and therefore authorizes the purchase.

If this is the correct algorithm, can't the terminal fake this pretty easily.  Instead of sending a bitcoin charge of 2 to the card, it sends a charge of 100.  The card returns 4200, the terminal determines the multiplication factor is 42, so it displays 84 to the user, who then validates the fraudulent charge.

You are correct except the secret number will cycle only between 1 and 9 and I will encrypt the number I send back so the terminal will not be able to read it.
Your attempt would also be limited to 6 times the user's median purchase or about 10-12 BTC.
It will probably be a simple Caesar cipher, but that should be safe enough for 8 characters ("1,23e-99" encrypted to say "A,AFeDBJ").

I estimate that most people will never use the card more than 10.000 times (about 27 years if you make one purchase per day on average).
If 1 in 500 purchases happens on fraudulent terminals (with most happening at trusted merchants) the PIN code will have incremented itself the next time you use a fraudulent terminal and even a network database of fraudulent terminals would need to collect data over a few years to decrypt the Caesar cipher.

With the maximum amount in place any such criminal effort is largely wasted.

To make high value purchases you could either pay simply using your normal BTC client OR use the card multiple times charging up to the maximum amount. (the median/maximum purchase amount will update exponentially upwards should you stubbornly try to buy a house with the smart card)

I don't get how Caucios coins blew up so fast. I mean anybody could make physical bitcoins and sell them, I don't get how he's on Bitcoin Wiki and everything.


OT: I'd definitely buy one of these, basically like a Physical Bitcoin Wallet aha. It'd be cool if there was a bar code, and then the BTC are loaded onto the card, so the only way to actually spend the BTC is if you had the card, and then there could be other security features added like a pin. iPhones, Androids, basically any phone with a camera have Bar Reader Apps to check prices on items and compare, so something can be developed.

Casascius came up with the concept of creating a holographic sticker that could have the private key imprinted on it and the coin holder would need to strip off the sticker in order to retrieve the actual bitcoin value.

It is not like he just stamped out a bunch of brass coins and sold them as "physical bitcoins".

And it was not really a business venture meant to me hugely profitable, more as a way to help bitcoin in general. He's on a lot of things related to bitcoin because he is involved in many things.

If it was as thin as a credit card and somehow managed to fit in a camera and eink display for QR codes then yes.

If it was bigger I wouldn't carry it with me everywhere but I might have one anyway to keep at home in a safe and as a souvenir.

yeah but anyone could do what casacius is doing, it's not like he has a patent or anything? What makes him so much better than all the other users, I mean I guarantee if I came up with that idea everyone would steal it off me. Is it just his reputation, because there has to be something that keeps everyone from making them themselves.

I'd change it from a card to device or some other wording to ensure people dont think the optimal use for this is in person physical purchases. I could see it being useful as something that is locked up in your house like having a bank at home, but would be scared as hell to walk around with bitcoins stored only on a card.

Agreed.

You would have a backup of the private key, so if the physical card gets lost or stolen, you just transfer the funds somewhere else before someone does something with them.

I'd rather it be set up as a bank type deal. If you had a back-up private key, that's just one more key you'll have to worry about. If there was like a database that stored your info like a bank, so if you lost your card you could call-in/lock your card so it couldn't be used. Basically the same thing as money but with bitcoin. Could happen, if people actually realized Bitcoins potential.

omfg... this is what makes me think maybe humanity doesn't deserve bitcoin. Maybe it's we need to generate an elite arms manufacture class , end up with the majority so poor the only option is the army to sort our lives out for us and keep us fighting against each other forever more. Too dumb for school!

The point of Bitcoin is to have cash in your control. Having keys stored somewhere not fully in your control... yes that is a bank. And that's the whole thing we're trying to address! Why not just sign up with a mywallet clone? Blockchain.info went to great pains to have the wallet local in the browser to avoid this.

There is multisig now. That means we can do things with a third party. A good way to have some extra security but don't take it lightly. Can that be used such that funds at an address be moved to a predefined address only? I would prefer to keep a portable card limited to spending funds and have the ability to top it up by SMS or some-such. It's better to be organized. But it is true that one of the most important things in security is convenience - we can improve here. Would someone like to give an insight into PGP server public key revocation and expirations and whether that's a good or bad idea.

The thing is, Bitcoin is cash so you have to treat it as such. Many people in the first world are used to having a company handle their finances... and get the big shock when those companies go bad once every 10-80 years. For some it will take some time to start handling finances themselves once again. I think anyone who doesn't is going to be wiped out pretty quick anyway. I find people who are poor are blocked out of financials anyway and having pennies focuses the mind.