The system depends on economic incentives. The miners who confirm transactions have made such a large financial investment—in buying computers to compete in the guessing game—that it wouldn’t make economic sense to undermine Bitcoin by entering false transactions. But that also means it does make economic sense to run tons of computers to guess random numbers in hopes of winning the Bitcoin reward. As one person famously put it on Twitter, “Imagine if keeping your car idling 24/7 produced solved Sudokus you could trade for heroin.”
