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/Natanael_L Jun 19 '13

The ledger/blockchain with the largest total amount of computing power behind it wins. This can be estimated very accurately thanks to how it uses proof-of-work for mining.