Topic: Bitcoin and Smart Cards - page 2. (Read 5135 times)

I wanted to add that 4 is also very important, the next malware will just do transactions vs steal keys without it.

How do you do that through said hypothetical compromised/evil reader/payment device?

Edit: I guess you could sign the message, but then you have to rely on trusting the receiver of the message to be able to verify the signature - making SMS an unlikely candidate.

Interesting, I would be interested in knowing more if you would be willing to share; as for your display statement could you elaborate on the assumptions around that

Not quite true. You just need some mechanism to convey amount out-of-band. Banks have been successful using amounts SMS'ed to a phone or robo-dialed to an automated voice system, for example. Not really a "secure display" and certainly not integrated into the point-of-sale unit / terminal. Yet still absolutely effective.

Yes this is another natural evolution of such a solution, I have worked on several "virtual" smart cards in my career some of which use phones. That said right now the phone doesn't offer great security,just consider all major phone platforms now have malware variants of their own.

This approach, at least today also doesn't provide the same mitigations, they can be thought of more as a portable flash drive; though to be fair Much of the value of a smart card is getting the keys off the host and these virtual smart cards can have that property. Developing one of these, at least one with reasonable usability and security properties requires platform work from the phone vendors that has not been done.

I've started working on such a project, but it won't be a card, at least not the early models.  Only items 1 through 3 in your list are really critical here, at least to start.  Also, a display built into the unit is absolutely critical.  Without it, there can be no security at all.

Yes they do, and it's possible to build systems where the card authenticates the reader cryptographically but such systems would require a arbitrator like Visa which philosophically may be hard to swallow in the BTC community. That said my interests are shorter term

Well now that might work - if it can show the amount of the transaction before it signs it.

Then again most everyone these days carries a mobile phone, so a phone + near field communication is probably the more "killer app".

As far as form factor I thought fob would be more interesting at first in that there is not a need to cary a reader around when you want to use your wallet. That said the technical implementation is the same, it's a packaging question.

There would be some technical changes necessary to things like the wallet file for example it would need to be able to contain references to private keys in addition to containing them but My goal with this thread was to gauge interest, and float price as part of that.


As for the ATM thing, on the surface it seams that the transactions of Bitcoin transaction prevent their use in a ATM like transaction without an intermediary making some sort of guarantee on the transaction. I can of course imagine that longer term but it's only viable in this model if the technical infrastructure is put into place and people are wiling to pay

You have to pay more for "secure display" capabilities but such devices do exist.

When per-account/transaction authentication is supported it would be nice to be able to use a smartcard or other trusted store (TPM, HSM, etc.) to launch the client (open encrypted wallet) and authorize transactions.

With the recent malware attacks on wallets themselves, attacking locally running bitcoind processes to make fraudulent transactions is sure to come next.

Multi-factor authentication and authorization as with smartcard systems you mention would be a convenient way to nullify this risk.

I am by no means an expert in smart cards at all, but I think the chief problem with this approach is that you still have to trust the device reading it. Correct me if I'm mistaken:

Say we're in the future where we can carry our Bitcoin wallet around on a smartcard. I go to Meze Grill, order something delicious and stick my card in the card reader. It asks me to agree to the 0.5BTC or whatever the future price of something tasty is, I tap "yes", it passes the transaction to my smart card and asks it to sign the transaction, before pushing it to the network.

Assuming I'm not misunderstanding something, so far so good.

Now what if the reader is compromised some way? With a smart card approach, there's absolutely no readout or anything of that nature that I can trust. The reader might ask me to agree to 0.5BTC and then ask my smart card to sign a transaction for 50BTC. The risk is reduced at brick and mortar businesses, but it's still there.

The risk is also there for credit cards of course, but drastically reduced because you can charge back credit card transactions that are fraudulent - you can't charge back Bitcoin (that's one of it's charms).

I definitely think pocket-wallet devices are a possible future for Bitcoin, but without them having a readout of the amount I don't think it'll work... and unless I'm mistaken they don't make smartcards with neat little screens on them.

The form factor would be very interesting. Having some kind of card implementation of wallet storage would be highly desireable. (At least, speaking for myself.) I would have to do more research on what would be required to get some kind of smartcard system going.

Heck, how about a bitcoin ATM that really is just a secure linux implementation that assigns coins to your card based on currency deposits?

My backgrounds is in security and specifically in authentication technology like smart cards, I have been watching Bitcoin for some time but the recent security issues has prompted me to take a closer look.

Bitcoins use an algorithm called ECC, specifically it uses ECDSA; this is the same algorithm that is used on the most recent DoD smart cards (though they use different input parameters to the algorithm).

With that in mind it would not be terribly difficult to apply these same cards (or at least a derivative of them) to Bitcoin. This can have a number of positive side effects for example in the the typical smart card design pattern one can say:
1) The key material is generated on the card
2) The key material never leaves the card in clear text
3) All operations using the key material happen on the card
4) Access to perform operations with the key material require authentication
5) Failure to authenticate locks the card preventing use by the attacker
6) Cards are designed to be both tamper evident and resistant to different levels of attacks

Basically when properly used the keys cant be stolen, transactions are restricted to the card owner; in other words the current issues of wallet theft would not be possible, that is without a rubber hose.

There are downsides to this approach, though they can be mitigated to various degrees, some of them include:
1) If you lock the card you may lose access to the key (and the associated cash)
2) If you loose the card you will lose access to the key (and the associated cash)
3) They have a limited storage capability (you can only have so many keys on the card).

Hardware comes in lots of different form factors, some are fobs (no card, they look like flash drives though they typically do not have storage) as well as the traditional card form factors.

The cost of the hardware varies (volume and capability are the two largest factors) but my best guess is under $50 a user, and much lower if it was adopted broadly by the community (as little as 10 per user).

The reason I started this thread is I am curious how much interest there would be in something like this.

Ryan