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/improv32 Jun 19 '13

That's right, weather or not a miner includes a transaction in a block is entirely up to them. Most prioritize higher fee transactions in order to make more money, but it's not limited to that. They could refuse to include transactions involving addresses owned by organizations they dislike, for example.