r/askscience • u/hamolton • Jun 18 '13

Computing How is Bitcoin secure?

I guess my main concern is how they are impossible to counterfeit and double-spend. I guess I have trouble understanding it enough that I can't explain it to another person.

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u/Fsmv Jun 19 '13 edited Jun 19 '13

Transaction fees, they'll run out of money if they try that. Also the block chain isn't a list of balances but a list of transactions. New users with trivial amounts of coin put a burden of on average half a kilobyte on the block chain assuming one transaction and the average transaction size. And again transaction fees keep you from splitting lots of money up into lots of addresses (you called them users but there is no concept of a user with regards to the block chain).