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Comment by pdog | Hacker News Reader

In reality, it takes more than a few seconds to charge a credit card.

Behind the scenes, the process of settling a credit card transaction after committing to it can take days. This is known as clearing.

Accepting a credit card after a few seconds is more like accepting a Bitcoin transaction as soon as you see it on the network (a 0-confirmation transaction), which is what some merchants do.

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Not exactly. Credit card authorization happens instantaneously, even though it takes the money a while longer to actually move between accounts. And this is separare from the chargeback mechanism, which can claw the money back after it's actually moved.

A 0-confirmation bitcoin transaction is more like writing down someone's credit card number and charging it later when you have access to your credit card terminal, which was common (in the form of those carbon copy credit card impressioning machines, which are why credit cards have raised digits) in the days before ubiquitous mobile Internet.

If you accept a 0-confirmation transaction and listen the network for a few seconds to ensure no double-spending transactions are broadcast, this is a reasonably secure way to accept those small transactions where 10-minute delay between blocks (resulting in a 5-minute average wait) would be a problem. Of course, you'd still better wait for 6 confirmations if selling a car.

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