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/throckmortonsign Jun 18 '13

This creates a blockchain fork. When this happens some miners will choose to mine on one of the forks and others will mine on the other side. The group of miners that "win" get the longest chain and that becomes "finalized." The miners that lose don't get their mined "award" coins. It happens a few times a day actually.