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Author Topic: BITCOIN ATM MACHINES  (Read 3059 times)
bitcon
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April 09, 2012, 04:21:51 AM
 #1

a bitcoin atm machine would be cool.   plug in your USB stick that contains your wallet.dat, and withdrawal the amount of Cash you need.   

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April 09, 2012, 04:27:22 AM
 #2

ATM would be cool, horrible implementation. Too easy for the ATM to record all wallet.dat files, then take people's bitcoins long after they've forgotten about the atm...

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April 09, 2012, 05:37:46 AM
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I believe the concept was that it would accept cash and spit out a BitBill with the particular amount of bitcoins sent to the card's address:

 - http://bitcoinatm.com

 - http://www.youtube.com/watch?v=FqpSZDMu5jY

I don't know if it was also to spit out cash as well though.  That type of transaction could only be done with either Green Transactions or by waiting until after waiting for multiple confirmations (e.g., more than 2 at least, probably at least 6 for any amount of size like $40 or more).

Now that we have OKPay and other debit card products that can be loaded with funds directly from bitcoin and withdrawn at ATMs, a specialized Bitcoin ATM might not be as badly needed.

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April 09, 2012, 05:57:22 AM
 #4

A better idea is for the machine to display a QR Code, you scan it and send your bitcoins to that address (using your own device), then you get your cash. Putting your private key data on a public machine is kinda dumb. The problem is that an ATM can't afford to wait several minutes for confirmation (though there are solutions).

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April 09, 2012, 07:09:35 AM
 #5

a bitcoin atm machine would be cool.

Working on it.

I think this could be a good solution for people travelling through multiple countries with multiple currencies on a trip. Convert bitcoins to cash or debit card on arrival, convert back to bitcoins on departure. Rinse and repeat.

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April 09, 2012, 06:57:56 PM
 #6

A better idea is for the machine to display a QR Code, you scan it and send your bitcoins to that address (using your own device), then you get your cash. Putting your private key data on a public machine is kinda dumb. The problem is that an ATM can't afford to wait several minutes for confirmation (though there are solutions).

Exactly!!!

Send coins to the machine from your phone, get USD cash. Doesn't even need to wait for confirmations.
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April 09, 2012, 07:02:09 PM
 #7

Send coins to the machine from your phone, get USD cash. Doesn't even need to wait for confirmations.

I am usually the one telling people that needing confirmations for all tx is silly.  Especially low value reversible ones.

That being said I have to think a 0-confirm ATM is likely a bankrupt ATM. 
Double spend = free money (literally). 

The defense of a double spend comes from the cost and complexity necessary to achieve it.   It likely isn't worth it to try and double spend a porn site or a McDonald's cheeseburger but I have think think double spending free cash is an attractive target.  Likely the most attractive target.
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April 09, 2012, 07:16:48 PM
 #8

a bitcoin atm machine would be cool.

Working on it.

I think this could be a good solution for people travelling through multiple countries with multiple currencies on a trip. Convert bitcoins to cash or debit card on arrival, convert back to bitcoins on departure. Rinse and repeat.

What about using a service like btcbuckets for it?
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April 10, 2012, 12:52:39 AM
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I wonder whether there are machines capable of accepting bills, and then dispensing those same bills later.  Cheesy

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April 16, 2012, 03:52:49 PM
 #10

I wonder whether there are machines capable of accepting bills, and then dispensing those same bills later.  Cheesy

Yes..  those exist..

They are becoming more and more popular..  But they are expensive compared to their counter part for the banks to purchase..

You should see one soon I would suspect, there are many out in the wild already.

I for one have already had training on how to fix them, yet have not touched one in the wild yet.  Smiley

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April 18, 2012, 04:03:22 AM
 #11

How awesome would it be to dynamically change the buy/sell spread on individual ATMs to ensure that you never HAD to go get cash from them. At some point if it got out of whack with market rates you would want to do the arb if no one else was of course. But in principle you could drop off a super duty cage somewhere and just let it churn money for you with no maintenance.

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April 18, 2012, 09:29:48 AM
 #12

That being said I have to think a 0-confirm ATM is likely a bankrupt ATM. 
Double spend = free money (literally).
Maybe it could be programmed to allow to have only X coins pending confirmation, it would greatly limit the incentive to attempt double-spends.
Or maybe you could send funds to the ATM while not being right in front of it, in advance, once the transaction is confirmed you get a receipt that is redeemable for cash at the ATM.

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Gerald Davis


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April 18, 2012, 12:56:53 PM
 #13

That being said I have to think a 0-confirm ATM is likely a bankrupt ATM.  
Double spend = free money (literally).
Maybe it could be programmed to allow to have only X coins pending confirmation, it would greatly limit the incentive to attempt double-spends.
Or maybe you could send funds to the ATM while not being right in front of it, in advance, once the transaction is confirmed you get a receipt that is redeemable for cash at the ATM.

The first one is a non-starter.  If the limit is too low the ATM is useless to any legit customer and yes some crooks will still attempt to steal a token amount of coins (ask Gavin the amount of fraud the bitcoin faucet gets and that is 0.01 max payout).  If the limit is too high all crooks will just steal that amount.

The second is a little more interesting and something I thought of yesterday when walking by a Rebox machine.  "Normal" ATM are mainly about impulse decisions ("oh crap I need $50") so having a call ahead normal ATM is kinda dubious.  A Bitcoin ATM is to provide planned fast exchanging of currency.  Nobody has a problem with reserving a movie online w/ RedBox.

A BTC ATM could operate in a similar manner.    You install an app on your smartphone (could also access it from any web browser).   The app generates a one time deposit address and current exchange rate.  You transfer the coins to that address via whatever client/wallet you like and the app provides you a "withdraw PIN" and block counter.   To use the ATM you just punch in your one time withdraw code (or have your phone send it via NFC or QR code).  Obviously other options are also available even optional magnetic cards/accounts for frequent users.

Now if you decided not to "pay ahead" you could at the ATM could replicate the same process except you will need to wait 6 confirmations.  Maybe have a 3rd party provide "double spend insurance" and allow the customer to cut that down to 2 confirmations for a higher convenience fee.

Obviously cash-> BTC tx would always be instantaneous.  Also as someone mentioned a smart ATM would adjust its exchange rates to reduce or eliminate the number of times it needs to be refilled by influencing customer behavior (maybe even allow users to sign up to learn when ATM has a good "deal").

The real problem w/ BTC ATM is density.  Normal ATM work because within 10 miles there are thousands of users with compatible cards.  I doubt there are many locations in the world where BTC account holder density is > 100 in 10 miles radius.

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April 18, 2012, 01:09:22 PM
 #14

That being said I have to think a 0-confirm ATM is likely a bankrupt ATM. 
Double spend = free money (literally).
Maybe it could be programmed to allow to have only X coins pending confirmation, it would greatly limit the incentive to attempt double-spends.
Or maybe you could send funds to the ATM while not being right in front of it, in advance, once the transaction is confirmed you get a receipt that is redeemable for cash at the ATM.

The first one is a non-starter.  If the limit is too low the ATM is useless to any legit customer and yes some crooks will still attempt to steal a token amount of coins (ask Gavin the amount of fraud the bitcoin faucet gets and that is 0.01 max payout).  If the limit is too high all crooks will just steal that amount.
For small amounts it's perfectly relevant, for big amounts I wouldn't trust bitbills (or any variant) anyway.
Regarding the hacking opportunities you're wrong, pulling off a double spend isn't exactly as easy as tricking the faucet, the ATM will just wait ten seconds in order for the first payment to be properly propagated.

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Gerald Davis


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April 18, 2012, 01:23:19 PM
 #15

Regarding the hacking opportunities you're wrong, pulling off a double spend isn't exactly as easy as tricking the faucet, the ATM will just wait ten seconds in order for the first payment to be properly propagated.

I never said it is as easy just that thieves will attempt to attack an automated system for much smaller amounts than valid users will be willing to wait.

It may be more beneficial to simply get users to accept the idea that the ATM is "phone ahead" rather than advertise the "instant benefits" only to have user find out that only $10 withdrawal is instant.  I am not sure the value of that anyways because 100 $10 withdrawals is $1000. Smiley  If a thief can double spend a $1000 withdrawal (finney attack for example) they could do the same for 100 $10 withdrawals.

Still I think a phone ahead ATM works fine.  It serves a different purpose/market.
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April 18, 2012, 04:55:11 PM
 #16

I would just charge a little more for instant withdrawals and use that as an insurance against double spends. Customers paying in advance would get better rates. Together with an amount limit for instant withdrawals you can keep your risk within an acceptable range.
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April 19, 2012, 05:21:22 PM
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I wouldn't worry about instant withdrawals from arbitrary bitcoin address, those people are going to have to wait. Instant withdrawals would be for people that have wallet accounts with the ATM provider, or maybe even networks of trusted wallet services.

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April 19, 2012, 05:27:49 PM
 #18

That being said I have to think a 0-confirm ATM is likely a bankrupt ATM. 
Double spend = free money (literally).
Maybe it could be programmed to allow to have only X coins pending confirmation, it would greatly limit the incentive to attempt double-spends.
Or maybe you could send funds to the ATM while not being right in front of it, in advance, once the transaction is confirmed you get a receipt that is redeemable for cash at the ATM.

The first one is a non-starter.  If the limit is too low the ATM is useless to any legit customer and yes some crooks will still attempt to steal a token amount of coins (ask Gavin the amount of fraud the bitcoin faucet gets and that is 0.01 max payout).  If the limit is too high all crooks will just steal that amount.
For small amounts it's perfectly relevant, for big amounts I wouldn't trust bitbills (or any variant) anyway.
Regarding the hacking opportunities you're wrong, pulling off a double spend isn't exactly as easy as tricking the faucet, the ATM will just wait ten seconds in order for the first payment to be properly propagated.
What if I create a transaction that should require a fee, but I don't include a fee with it?  Then the transaction is propogated with 0 conf, but it'll never go through.  In the meantime, at some point afterward, I can create another transaction with a fee sending those coins to my own address.  Viola!  Free cash from the ATM.

I wouldn't worry about instant withdrawals from arbitrary bitcoin address, those people are going to have to wait. Instant withdrawals would be for people that have wallet accounts with the ATM provider, or maybe even networks of trusted wallet services.
I would agree with this.

Think of it as a bank.  You have a bank account balance, and those are the funds you use to interact with the machine.  You can't withdraw from the ATM unless you have funds in your bank account.  Same as it already works with cash.

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April 19, 2012, 10:53:57 PM
 #19

For small amounts it's perfectly relevant, for big amounts I wouldn't trust bitbills (or any variant) anyway.
Regarding the hacking opportunities you're wrong, pulling off a double spend isn't exactly as easy as tricking the faucet, the ATM will just wait ten seconds in order for the first payment to be properly propagated.
What if I create a transaction that should require a fee, but I don't include a fee with it?  Then the transaction is propogated with 0 conf, but it'll never go through.  In the meantime, at some point afterward, I can create another transaction with a fee sending those coins to my own address.  Viola!  Free cash from the ATM.

Solution: Have the ATM refuse to pay out on unconfirmed no-fee transactions, and instead have it print out a receipt with a QR code that can be redeemed for cash at the same ATM after the transaction gets confirmed (if it ever does).

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April 19, 2012, 11:07:49 PM
 #20

For small amounts it's perfectly relevant, for big amounts I wouldn't trust bitbills (or any variant) anyway.
Regarding the hacking opportunities you're wrong, pulling off a double spend isn't exactly as easy as tricking the faucet, the ATM will just wait ten seconds in order for the first payment to be properly propagated.
What if I create a transaction that should require a fee, but I don't include a fee with it?  Then the transaction is propogated with 0 conf, but it'll never go through.  In the meantime, at some point afterward, I can create another transaction with a fee sending those coins to my own address.  Viola!  Free cash from the ATM.

Solution: Have the ATM refuse to pay out on unconfirmed no-fee transactions, and instead have it print out a receipt with a QR code that can be redeemed for cash at the same ATM after the transaction gets confirmed (if it ever does).
What happens if the transaction doesn't need a fee, and the client doesn't include one (since none of them do by default unless it is needed)?

What if you send a transaction with a fee to the ATM and withdraw the money, but then send another one with a higher fee to yourself, banking on the rules of various mining pools to push the higher fee transaction through first?  Even if it only happens 10% of the time, you could make bank just doing transactions with the ATM over and over, waiting for that one chance of your second transaction going through before your first.
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