Topic: What's the best technology to use for a face-to-face BTC transaction. (Read 5013 times)

I think that at this time, a good percent of the people who have the number of BTC that I would want are perhaps not the kind of people I would wish to spend a lot of time hanging out with.  I'd just as soon pass on being the target of a 'three-pronged attack', for instance.

Exactly, you said it 

Yes, I also like that option. It promotes human contact and social interaction. Everybody is in such a rush these days...

i would happily wait an hour if it's a really large sum, invite the other person a coffee, take a walk or something else. we could turn more social using this system, you never know

Finney attack

I don't need superhero abilities, just a decent amount of computational power It is obviously not simple and may not be practical to do, but if you are relying on this "instant transaction" to make large deals (several thousands of dollars) you may be defrauded. You need to wait for confirmations on the transaction to your personal account.

EDIT: The general idea of the attack is that I am pre-mining blocks which include the transaction from my address A to my address B, but I don't release them. Then I give you the private key/wallet to my address A. You give me the money and send a transaction from the address A (which you now control) to your address C. As soon as I "hear" your transaction spending the coins in A, I release the block with a transaction from A to B, which invalidates your transaction.

@nmat, if i import the key pair you generated and charged with funds into my wallet and set it on auto, make a transaction to transfer funds on one of my personal accounts, how would you double spend the coins without having some superhero abilities of some kind ?

@adamstgBit has been talked a few times, we already have covered the communications channel named Internet no need to reinvent things again, we need ways to transfer our bitcoins over other channels like air for example. Internet technology already thinked of that too and resolved it by "encapsulating" the message in a good transporting package, a bitcoin wallet stored on a usb flash memory or CD would do.

i still think e-mail method should be put in the client. it sound relatively easy to implement, and it adds user friendliness,

poeple lost a lot of coins because of user error while backing up a wallet...

the bitcoin client should implement solutions for all the reasons we play with the wallet.dat, as to prevent Human error  .. and Third Party Error!

The problem with all that export/import stuff is the double spend. If you import my key into your wallet I can still spend the coins. If you transfer the coins, I can use an attack with a pre-mined block that invalidates the transaction.

Since you need to wait for confirmations anyway, I also prefer DeathandTaxes' method. And you can use green addresses if you don't mind the "centralization".

one time wallets should be developed, as part of the client... maybe even throw in a button |email| 1BTC - To: [email protected] - encrypt wallet OFF!

easy payment, fun payment


addendum:

E-mail was revolutionary when it went main stream,
Bitcoin just makes Everything a little Bit:better

 

agree with you DeathAndTaxes, you mixed seller with buyer though

While alternate methods involving exporting keys, and one time wallets might develop....

smartphone adoption will continue to rise.  Hell TMobile has $99 android phones without contract.  That will continue to fall.  In 2-3 years I expect to see $59 smartphones without contract.

At some point there will be little reason to get a "dumbphone".  The type of people who would be attracted to Bitcoin are attracted to smartphones and other gadgets so my guess is smartphone adoption among "bitcoin population" is higher than general population.

I think in 2-3 years most face to face transactions will be like this

a) buyer generates QR code from his Android wallet for onetime public addresss.  This will be as simple as pushing a button/icon for "accept onetime payment"

b) seller uses scan QT code option in his Android wallet which auto opens a payment field with address, payment amount, and possibly a plain text note "used 5970 graphic card" embedded in QR code by buyer.

c) seller reviews transaction and inputs pincode/passphrase.

d) in <5 minutes 0 confirmation transaction appears in sellers wallet.  If necessary parties wait for x confirmations but most small transactions will likely be handled with no confirmations.

Other than waiting on confirms both parties accomplish the goal safely, securely, and in a matter of minutes.

it's hard to find a solution, i know, cause bitcoin it's in our computers and heads. Until we can easily import private keys into pc client, android or any other type we will have to deal with it a little awkward.
Would be nice to have an export sum of bitcoins to file. For example hit export, enter amount and client would be writing a  .btc onto your usb stick containing public address and private key. Hand the usb to a seller, he hits import from usb, rescan the blockchain on the fly and spend the amount in his wallet. Hands over the usb stick without that file on it.

I'm sure a bitcoin light client for RIM would go out in no time and all teenager girls will have the ability to go shopping only with that piece of expensive hardware on them.
I trust my smartphone, until we find a real easy solution, and i recommend everyone have one, even my 50 year old parents have one and at first used them only to make calls, now do everything you can do with them and don't complain that much

fixed that for you

I think the different methods suggested have different strengths and weaknesses. The strength in this one is no third party required. It probably takes a little more setup than the instawallet method suggested, and you might want to wait for a confirmation. With the instawallet method you don't need to wait for confirmation (as long as you have come to trust instawallet).
So it's swings and roundabouts - it seems to me that no one method is better than all others in all respects.

That's just like accepting 0 confirmations. It may be more simple though because it doesn't require smartphones and Internet during the trade.

Spam filter


Actually I like that idea ...  You just need to triple check that the copy you got wasn't already spent....

I am envisioning a situation where I have, say, several thousand cash, or some PM's, or whatever.

When the other party and I meet, I give him some cash, he gives me some BTC, then I give him some more cash, he gives me some more BTC, etc.

At the end, he is in the same position I used to be.  That is, he's sitting there with a wad of cash and is vulnerable.  So, meeting in a public location is desirable, as is having the ability to incrementally deliver both BTC and the goods in a fairly rapid-fire and secure method is what I would be looking for.

I believe it to be the case that transferring BTC from one instalwallet to another is rapid and reliable.  I would probably be immediately transferring value out of my Instawallet even as the transaction was underway.  This would be at best cumbersome to accomplish by handing over pre-generated wallet.dat files.

but why take a risk?

the buyer e-mails you his wallet.dat (which has a password on it *now avaible with the new client 0.4.0)
when the buyer get's to your place all he has to do is tell you his password, and you can transfer the funds.

anyone see a problem with this dead simple method?

The best technology to bring to a face-to-face BTC transaction is enough muscle to make it not worth the risk to attempt a robbery, and a location where one would be cumbersome.

Beyond that, I should think that a simple transfer using something like instawallet would be fine, but have not really researched the service for larger BTC transactions.  If Instawallet pulled a MyBitCoin in the 20 minutes or so that I would need them to be working, that would suck, but a risk one takes I suppose.

maybe have the buyer prepare a wallet.dat with the agreed amount, which he will save on a usb

when he gets to your place, take his wallet.dat from the usb he brought and transfer the funds.

end of story?

EDIT: the user could also e-mail his wallet.dat to him self, if he doesn't have a usb

another idea! Dead simple

the buyer e-mails you his wallet.dat (which has a password on it *now avaible with the new client 0.4.0)

when the buyer get's to your place all he has to do is tell you his password, and you can transfer the funds.