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Author Topic: What's the best technology to use for a face-to-face BTC transaction.  (Read 4572 times)
FreeTrade
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October 28, 2011, 11:18:26 AM
 #1

Let's say I've sold you my old collection of VHS Ally McBeal boxsets on eBay.

We've agreed you're coming over to my home to collect the goods and to pay the Bitcoin in person.

What's a good technology set-up for us both to minimize hassle?

Let's assume there is a Wifi and PC at my home. Interested in practical solutions where a) buyer does have a Smartphone b) buyer doesn't.

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October 28, 2011, 11:22:39 AM
 #2

make the buyer get his laptop or smart phone over to you. give him the address, and ask him to send the bitcoins.

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October 28, 2011, 11:23:25 AM
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bit-pay
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October 28, 2011, 11:32:14 AM
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make the buyer get his laptop or smart phone over to you. give him the address, and ask him to send the bitcoins.

So the buyer must have laptop/smart phone. And how to give him the address? SMS, Email or is he going to key it in? How am I to confirm, how long to wait?

Think about the practicalities. Maybe I have 20 or 30 people picking up items that day - I want something streamlined that I'm not fiddling over each time.

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October 28, 2011, 11:41:37 AM
 #5

bit-pay

That looks promising, but appears to require a third-party intermediary (and two smartphones with internet connectivity).

Am looking for the best way to send bitcoins rather than a promise from a third party to send bitcoins at a later point.

The internet is freedom to communicate without permission. Crypto is freedom to trade without permission.

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October 28, 2011, 11:46:23 AM
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Casascius or Bitbills?

I know this because Tyler knows this.
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October 28, 2011, 11:49:42 AM
 #7

First things that come to my mind:
* your trading partner might not trust your internet
* he might not have a smart phone
* he might even not have a printer

What he can do though is charge an instawallet with an easy to remember secure link.
MyPaymentForThatAwsomeVHSCollection

He wouldn't even need paper on him and you may transfer that money to your wallet while he is at your house.

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October 28, 2011, 11:54:15 AM
 #8

Casascius or Bitbills?

Good idea! Ask your buyer to get those stone age physical money tokens! Wink

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October 28, 2011, 12:00:23 PM
 #9

Buyer really should bring a smartphone. Then you just use the Bitcoin app.

Bit-pay is very handy if both have cell phones.

The third party thing is no big deal since they send you either cash or Bitcoins at the end of the day.

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October 28, 2011, 12:11:58 PM
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Casascius or Bitbills?

Awkward to acquire in advance and difficulty with change. Also counterparty risk (third party again).

The internet is freedom to communicate without permission. Crypto is freedom to trade without permission.

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October 28, 2011, 12:14:38 PM
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What he can do though is charge an instawallet with an easy to remember secure link.
MyPaymentForThatAwsomeVHSCollection

He wouldn't even need paper on him and you may transfer that money to your wallet while he is at your house.


Interesting - so he'd preload a wallet with the agreed amount, and then he'd give me the keyphrase, which I'd enter into my browser and transfer the funds.

Think this is the winner so far!

The internet is freedom to communicate without permission. Crypto is freedom to trade without permission.

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October 28, 2011, 12:17:07 PM
 #12

Smartphone or laptop, that's all. You give him your address and done. I suppose he has enough brain to be able to type your address in the phone... If he is so idiot, print it in a qrcode.

The wallet idea is nice but less safer. He give you the wallet with the btc inside it but unless you move that btc in another wallet, he can still move them in another wallet...
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October 28, 2011, 12:17:37 PM
 #13

* your trading partner might not trust your internet
no big deal.

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October 28, 2011, 12:22:14 PM
 #14

Buyer really should bring a smartphone. Then you just use the Bitcoin app.

...

android smart phones are the most reliable for making this kind of transactions, you let him scan you address qr and send payment over his 3G or your wifi internet, doesn't matter actually because bitcoin is designed to work in a non-trusted environment.
You should chat or invite the buyer a coffee while you wait for confirmation (10-20 minutes). It makes you be more social in the end cause you have to be in contact while you wait for that confirm

edit: option 2 would for the buyer to handle you an usb stick with a wallet.dat file that has the wanted amount. You could close your client, swap the wallet with a symbolic link, start the client again with a -rescan param, transfer the funds to an address you own.

edit2: i proposed the only options i would trust in a face-to-face transaction  Smiley

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October 28, 2011, 12:37:14 PM
 #15

Buyer really should bring a smartphone. Then you just use the Bitcoin app.

...

android smart phones are the most reliable for making this kind of transactions, you let him scan you address qr and send payment over his 3G or your wifi internet, doesn't matter actually because bitcoin is designed to work in a non-trusted environment.
You should chat or invite the buyer a coffee while you wait for confirmation (10-20 minutes). It makes you be more social in the end cause you have to be in contact while you wait for that confirm  Cheesy

Okay, so I'd have a print-out of my bitcoin address qr handy (maybe made with Wolfram Alpha) and the buyer scans it and enters the amount - what app is the buyer using on his Android smart phone?
I'm confirming, say on my PC - but need to wait 10 or 20 minutes.

This sounds workable and has the advantage of no counterparty and we can change the amount easily if we're haggling. Only disadvantage is that it requires a smartphone.

The internet is freedom to communicate without permission. Crypto is freedom to trade without permission.

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October 28, 2011, 01:03:13 PM
 #16

This is harder to do right now because it involves tools outside of the normal client right now, but I think eventually it might be common for these kinds of things. Similar to the Instawallet idea, the payer could create a "Paper Wallet" with an address and private key (The easiest way I know of to make a private key & address pair right now is an external program like vanitygen or https://www.bitaddress.org/ though you need to either trust their code or verify yourself that it's correct). He sends to the address the amount that he wants to spend, and then just gives you the private key when he gets there. You redeem it by entering it into an online wallet like Mt. Gox or, if you have the key import patch applied, importing it into a new wallet and transferring the money to your normal wallet.

You in theory should wait for confirmations if the payer is trying to scam you, but they'd have to be trying to pull off a double-spend attack. I think for most person-to-person secondhand sales, you've got about the same risk as the chance of them paying you in counterfeit Federal Reserve Notes. It could happen, and you could wait for a confirmation to make it much less likely, but I doubt that it's worth waiting for more than 1 confirmation, and for most items you probably don't even need to wait for that.
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October 28, 2011, 01:14:06 PM
 #17

Edit: the solution applies to scenario "b" in the OP

I don't know what tools can currently do this (if any), but the following would seem the best way: 1) have the person send the bitcoins to a new address, 2) have them print a QR code that encode the private key, 3) meet up and provide you with the printed QR code, 4) scan and sweep the funds into your wallet.  A tool that makes this easy would be nice...it would make use of the casascius shortened key format if the size of the QR code is a problem.

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October 28, 2011, 01:17:13 PM
 #18

Quote
I don't know what tools can currently do this (if any), but the following would seem the best way: 1) have the person send the bitcoins to a new address, 2) have them print a QR code that encode the private key, 3) meet up and provide you with the printed QR code, 4) scan and sweep the funds into your wallet.  A tool that makes this easy would be nice...it would make use of the casascius shortened key format if the size of the QR code is a problem.

Or you could just tell the guy to send it to flexcoin id : president or whatever...

It's the whole reason we built flexcoin is for mobile payments.    QR code support,  etc..   or you could lug around a laptop .... 



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October 28, 2011, 01:18:08 PM
 #19

Buyer really should bring a smartphone. Then you just use the Bitcoin app.

This.

Buyer needs to be sending coins from equipment he owns/controls.  Not doing so is dangerous.  If Buyer uses seller's computer (hey just log in to this computer here) to pay via a waller he needs to trust seller not to perform MITM attack.   For extra security buyer shouldn't connect to seller wifi (instead use smart phone 3G connection).  

To make getting correct BTC address to pay to most smartphone bitcoin wallets support scanning a QR code.  You simply give the buyer a QR code to scan and he sends coins to that address.

This way both parties use trusted equipment and independent network streams.  Neither system connects to each other (air gapped).  The "trust" only happens in the blockchain.  Both parties trust the block chain thus don't need to trust each other.
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October 28, 2011, 01:21:15 PM
 #20

Buyer really should bring a smartphone. Then you just use the Bitcoin app.

This.

Buyer needs to be sending coins from equipment he owns/controls.  Not doing so is dangerous.  If Buyer uses seller's computer (hey just log in to this computer here) to pay via a waller he needs to trust seller not to perform MITM attack.   For extra security buyer shouldn't connect to seller wifi (instead use smart phone 3G connection).  

To make getting correct BTC address to pay to most smartphone bitcoin wallets support scanning a QR code.  You simply give the buyer a QR code to scan and he sends coins to that address.

This way both parties use trusted equipment and independent network streams.  Neither system connects to each other (air gapped).  The "trust" only happens in the blockchain.  Both parties trust the block chain thus don't need to trust each other.


Look at the conference I sent my bitcoins from my iphone using the flexcoin system to the bit-pay system ... funds got there in seconds....   We have several thousand users that use it specifically for person to person (IE: in a bar) bitcoin transfers.   as noted it has QR support even if you didn't want to type in the guys username.

Lug around a laptop or try to make some huge system work... or just flexcoin it...  but do whatever you guys want..  I can only tell you what I do and a few thousand people do.    It supports QR codes,  it even supports the iphone "bookmark icon"  it's specifically designed for mobile.   You can even send bitcoins to an e-mail address...







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