I would not doubt that gross emotional responses could be detected in humans.  Like 'love of Big Brother' for example.  I'm actually a little surprised that the technology does not exist now or if it does, that it's not used to ferret out the likes of Snowden before he was given root access to the machine.

Beyond that, I would not rule out the possibility that thoughts which are formulated through semi-vocal means within the mind might be tapped with some amount of precision.  At some point anyway.

With bitcoin, a double spend isn't guaranteed to work. It all depends upon which transaction gets to the miner first.
And if you do it frequently, you will get caught because cameras are all over the place and you will be identified.

Perhaps for low value thefts you won't be but that's peanuts.

And as far as credit cards go, the problem is stolen credit cards.
You can buy lists of valid credit card numbers (something that doesn't really work with bitcoin) so you can keep defrauding the same way you would with double spending.

-=-

Some silicon valley exec just got busted for stealing legos. How was he doing it? Printing barcodes that scanned at lower prices and pasting them on the boxes so they ring up cheaper.

Thieves will always find a way.

You know, the more I've been thinking about this the more I'm convinced that confirmation time is an imaginary fear.

When someone sends me bitcoins, I see that they have sent it almost instantly. That doesn't validate it is not a double spend but it does validate that they have the bitcoins needed to spend, does it not?

Doesn't the P2P network block a forgery transaction that has a made-up input? Wouldn't my client know the input was invalid?

So at least I know the input is valid. What I don't know is if the sender will double spend.

That's almost exactly the same thing with credit card authorizations

They may be instant but I don't know the value is really mine for some time. The authorization can be cancelled and even after it is paid it can still be reversed. How is that any less risky than someone doing a double spend?

There's no difference between accepting 0 confirmations and accepting with just a credit card auth. None at all. In both cases the vendor is taking a risk that they won't get the money.

At least with bitcoin the window of time is much smaller for the vendor to actually know the payment is good.

Just use whatever email you like and encrypt your message. Encourage your recipients to do the same.

confirmation bias
http://youarenotsosmart.com/2010/06/23/confirmation-bias/

Spend a few hours at that site and realize how stupid we all really are.

You may not like the current implementation of green addresses, but it's actually very easy to use multisig to make user-specific green addresses where your money can't be stolen, or frozen (if the cosigner disappears of the internet) for more than a few days. If that ends up being required to keep zero-conf safe, it will be deployed and used widely. We don't need to introduce new features to deal with zero confirmation security.

And your "Instant Bitcoins confirmation time" would keep them from putting products in their pocket and walking out of the store?

If it is a problem a solution already exists, use of a green address. Usually they are offered by web wallets but they don't have to be.

I don't think it will be a problem in South Africa either. Or even Uganda or Nigeria or anywhere.

I just need to rant for a second...

 

I go to make a purchase at a place we buy from regularly this morning - using Paypal.  Instead of working, I get a message that the payment is declined, because I have hit some sort of limit, and now I need to verify my account!  I check my history, and there is nothing unusual there - no large transactions, just many small ones over the lifetime of the account (several years).  Checking the balance, we have spent nowhere near the stated limit in the past 12 months, so I can only assume they have a LIFETIME sending limit on their account - once you hit it, you need to verify.

On the Paypal site, there is a nice little banner informing me of this fact, and saying its easy to lift the limit - BY PROVIDING MY BANKING INFORMATION!  I am not providing that, as they have no business knowing it!  I have linked a credit card to the account for years now and have never had a problem.  Now the account is unusable, without providing that information!   They so screw over their customers!  I don't want to use them, but they have been the most convenient method of payment over the past several years.  They are making it so easy to see the advantage of using Bitcoin!


Now, more on topic for a second - this business is actually a place that I had contacted about them using Bitcoin, as they have mentioned that their fees are so high they encourage people to use checks rather than Paypal.  They do know about Bitcoin, and the people involved are interested, but unfortunately the other customers are already giving them such a hard time about how to use Paypal, that they (understandably) don't want to open a new can of worms with Bitcoin.  (FYI - The business is a CSA - a farm share, that provides fresh local fruits and vegetables to their members).

Oh, I so hope that we can see the end of Paypal - SOON.  Hopefully I'll have luck convincing the CSA to accept bitcoin sometime soon!

And this is a problem?

They already have. And since bitcoin transactions happen over a network, you may even be guilty of wire fraud if you did a double spend attack. That's much more serious than just stuffing something in your pocket.

But just because it is possible to double spend doesn't mean it will be a common occurrence. Most grocery stores where I live now have self checkout lanes that aren't even monitored. Does theft happen? Sure. But most people don't try to steal.

Not rich until they got it converted to some hard USD

Now theyre just holding a hot potatoe

Exactly, zero confirmations.  This should be good enough for most point-of-sales purchases (like groceries) in my opinion.  As AliceWonder has outlined, if someone intends to steal low-value items from the shop, they will surely find a much simpler way than performing a double spend.  So confirmations are really only necessary for high-value purchases like cars or high-end electronic products and so, where the effort and risk associated to a double-spend is worth it.  In that case (think a car) it isn't a big problem to wait for the confirmations.

The solution is green address.

Actually the solution is to not worry about it, it is really just another form of shoplifting. People who want to steal will find a way, and going through the register line is a bad way to do it because most places you will be caught on camera and eventually caught by law enforcement.

But double spends will be rarely attempted and I suspect the losses will likely be less than what is currently lost in debit/credit card transaction fees and chargebacks.

It doesn't cost anything to make a transaction. An attacker can create 1000 double spends.

Computer code cannot detect which is the "legitimate" double spend or which is the "attacker" double spend. They only know which transaction they themselves heard first.

OK.  I totally believe you have a 160 IQ now.

Seriously, the smarter you are it seems the more bored people are in high school.  In my experience it seems those that have the best grades are the ones in the 120-130 range.   I was just barely above that so my grades were OK but not great.  I did not care that much.  I was shocked when I graduated with honors.  I was like, "How did I do that?"  I was not really trying to.  I felt a little guilty then.  I often think if I had only applied myself I guess I could have graduated at the top?  But I did not care that much really.  In fact, after taking one AP class I realized I was working harder for an "A" and it would be much easier to just take a normal class, not study at all and get an A or B.  I guess I was a little "lazy" too.

I would love for people to start using Bitcoin on the high street, my life would be so much better in so many ways. But waiting even 10 seconds for a transaction (EFTPOS, VISA, etc....) is unacceptable. We either use 0 confirmations with at least the minimum fee and let the customer walk straight away or use a layer on top such as Bitpay. (If this takes off eventually VISA and MasterCard may support Bitcoin too)

The added benefit of a layer on top of Bitcoin is that we can pay in Bitcoin and the merchant can choose to have the transaction instantly converted into local fiat or remain as Bitcoin. (This will increase adoption)

If people are forced to wait 10 minutes for Bitcoin transactions ever (on the high street) this will forever destroy the reputation of Bitcoin in the minds of normal non Bitcoin people.


If the first transaction is 0 fee it might take some time to be included into blocks, the double spend with a fee then propagates faster before the first confirmation and eventually >50% of the network will see only 1 transaction. This might not happen all the time but it makes automated detection of double spends difficult. Your idea relies on the Bitcoin network always being able to detect the double spends correctly.

Also how do you move the coins without having the private key? This might be the most difficult part of your idea.

No need for the agression. There must be a third party in your idea or how else will the network determine the double spend? To the network it will eventually just look like 1 transaction with no guarantee enough nodes saw 2 transactions. So there is no way to automatically flawlessly detect a double spend, a third party is essential to settle disputes. Also your idea with no third party requires code to send coins from addresses without needing the private key which has far too many security implications.

Also if the standard is that people without double the money they are spending in store having to wait 10 minutes, 95% of people will be waiting 10 minutes. Not sure where you are from but most people I know live paycheck to paycheck and a grocery shop after rent and fuel does not leave much.

Also I do not work, have not invested and have never even used bitpay. I have heard how it works and see bitpay as a possible future for point of sale, especially if the merchant does not want to hold Bitcoins at all.

If the transaction has a fee, the chance of a double spend working is much smaller. Very few double spends have ever worked (I think S.Dice dealt with a few)

Also the longer you wait (in seconds) the more miners pick up the transaction with the fee, a second transaction with a even with a larger fee would not be included because the first has already been propagated. This all happens before the first confirmation mind you, once that happens no double spend will work (would take a lot of coordination to double spend a loaf of bread (When waiting for you Bitcoin house purchase please wait for at least 3 confirmations))

But about your idea and why its bad. You're plan is to put some of the customers balance at risk every time they purchase something, and for a third party to mediate this. The alternative is far easier on everyone involved. Use a service like Bitpay, they take on the risk of a double spend (very unlikely, remember bitpay is connected to many more nodes than you are) and can cover the odd double spend with their profits.