Bitcoin Forum

So how would bitcoins be adopted in irl stores given that their transaction time is like 20 minutes?
You'd be buying soda and chips at the store, pass your bitcoin smart card and then just sit and wait?

yes this seems to be the major drawback of bitcoin as a transactional currency as far as I can tell.

And even if you just wait for 1 confirmation, it takes awhile.  And if you don't wait for any, you are risking getting scammed by "double spend" so not sure there is a way around it.

When thinking about a simple double-spend of 0-confirmation transactions, the ~10 minute wait is still much better than the two-month wait in case of credit cards. That is right. Merchants are at risk of fraudulent chargebacks by the customers for months after the transaction. Yet, credit cards are thriving. Why then do we see ten minutes as a problem with Bitcoin?

Also, look at the replace-by-fee proposal (https://bitcointalk.org/index.php?topic=179612.0). Interesting stuff.

The problem with this is that it typically costs money to issue a chargeback by the buyer. If the buyer was buying something for under 25$ (which is probably about 90%+ of all payments made in a day) then 90+% of all transactions are safe because a chargeback usually costs 25$. But in the problem with bitcoin in this case is that 100% of can be double spent without any cost to the buyer.

I hate it when I go to the store and pay with a credit card, I have to wait until the next day when the money is deposited in the grocery store's account when the transaction is confirmed.  I usually bring a sleeping bag.

What is the risk?  What is the cost of scamming a small transaction on a double spend?  What does it cost to execute a double spend?

If you answer those questions, you'll realize how ridiculous your point is.  My guess is you don't know the answers, otherwise you wouldn't say such things.

what's double spend. Does it actually happen?

zero conf double spend works like this:

A buyer sends a payment to the merchant address.

Buyers address: 1aaa = 1BTC

This transaction contains no fee or a very small fee to ensure it takes a long time to get confirmed. As long as the transaction is not confirmed the buyer still owns the money.

The merchant will see that the transaction has been broadcast to the network and is waiting for confirmation. Since the merchant allows zero-conf transactions the buyer is free to leave with whatever the buyer "bought".

Merchant address 1mmm = 0BTC (1BTC waiting to be confirmed)

The buyer then creates another transaction using the same input address (1aaa) sending the money (1BTC) to a different address than that of the merchant. With this transaction a high fee is added thus increasing it's chances of being confirmed first.

If the new transaction gets confirmed first the old transaction is no longer valid as the address 1aaa no longer has 1BTC assigned to it and in so the network will never confirm it.

The buyer aka thief has just stolen 1BTC worth of goods from the merchant with incredible ease.

I think the transaction time is a major drawback right now. I sent coins 15 minutes ago and still unconfirmed

edit: this is also why I think bitcoin will be used more as wealth storage rather than a daily transaction method. Things like Litecoin are much better for day to day transactions because of the quicker times

I've used bitcoin at retail locations a bit. Merchants tend to accept 0-conf transactions for "everyday" transactions (eg, for lunch), no problem.

So I scan their QR code, hit send, a few seconds later they see the transaction come through, and we're done. No one has demanded waiting around for 1 or more confs.


As others have noted above, the reasons are pretty simple:

1) Merchants are already exposed to MUCH more severe charge-back risk from credit-cards.

2) The risk of someone mounting a double-spend attack against the merchant are quite low. It would take a good deal of technical sophistication to even try, much less succeed.

More importantly the network does not cooperate with any attempted double spends. Right now, the first attempt at spending a specific coin will be the only one that gets relayed, any subsequent attempt at spending it is dropped. There is talk of actually spreading a warning when a double spend is attempted, so that not only would you not be able to double spend the money, but also the merchant would be quickly warned that you attempted to do this.

https://en.bitcoin.it/wiki/Double-spending (https://en.bitcoin.it/wiki/Double-spending) has a lot of details on different threat models and how to avoid them. General rule of thumb is zero conf-doesn't take a long time to be safe, as long as the value of what's being sold is low relative to the value of a block.

How do credit cards work when the confirmation can take 180 days?