user11276: Since multiple values can result in the same hash, couldn’t an attacker try to find a way of increasing his balance in a way that the checksum of the changed block remains the same (so that any proofs-of-work are still valid) and then propagate the change into the network without peers noticing it?

user85: Sure, he can try. But the algorithms Bitcoin uses were specifically chosen to make this attack completely impractical. It would be trillions of times easier to just buy the Bitcoins.

11276: <p>Since multiple values can result in the same hash, couldn’t an attacker try to find a way of increasing his balance in a way that the checksum of the changed block remains the same (so that any proofs-of-work are still valid) and then propagate the change into the network without peers noticing it?</p>
 85: <p>Sure, he can try. But the algorithms Bitcoin uses were specifically chosen to make this attack completely impractical. It would be trillions of times easier to just buy the Bitcoins.</p>
