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It is theoretically possible to double-spend a bitcoin transaction in the first 20 minutes after you spend it. However, the cost of doing so (in processing pow
by AndrewDucker 13y ago
It is theoretically possible to double-spend a bitcoin transaction in the first 20 minutes after you spend it.
However, the cost of doing so (in processing power) is high enough that it's not worth doing for small amounts. So long as amounts over $100 wait for confirmation you should be fine.
- davmre 13y agoI don't understand where the cost comes from. Can't you double-spend at will until one of your transactions makes it into the blockchain? Until that point, as far as the Bitcoin network is concerned, you haven't actually spent any money. So it seems like you'd have ten minutes or so of double-spending ability, totally free, and only have to start using processing power if you want to extend beyond that ten-minute period (by forking a blockchain that excludes the transaction you intend to double-spend). My understanding of Bitcoin implementations is pretty vague, though, so I'd welcome correction if this isn't actually how it works.
- AndrewDucker 13y agoNope, you're right - you need a single confirmation before it would cost to double-spend. I was misremembering.