So what would happen if someone with massive computing power (say, a supercomputer or custom hardware) slammed the network for 2016 blocks, and then stopped?
Would the difficulty adjustment make the next 2016 blocks possibly take months or years to process? (just a possible type of DOS that someone with a supercomputer might do). Something like this might happen when the bonus per block goes down to 25, a bunch of people might take their hardware offline because it's not profitable, so it could take a long time for the difficulty to readjust.
Would the difficulty adjustment make the next 2016 blocks possibly take months or years to process? (just a possible type of DOS that someone with a supercomputer might do). Something like this might happen when the bonus per block goes down to 25, a bunch of people might take their hardware offline because it's not profitable, so it could take a long time for the difficulty to readjust.
There is also an adjustment limit to impede just this kind of thing. The difficulty is not permitted to adjust more than 4 times up or down (one-fourth) in a single adjustment. So if an attack such as this were to happen, the worst that could be done by an attacker with limited access to supercomputing level resources is to extend the two weeks to eight weeks; and even this would require some serious firepower, considering the current difficulty implies that the network is already supercomputer class on it's own. In order to do more, the attacker would have to be willing and able to dominate the network for two or more adjustments. We are talking nation-state level capabilities right now, and at the rate of current increases, it will not be long before most nation-states wouldn't have that kind of collective power at their singular command.
Even if this were to occur, the current generation isn't likely to just stop. Most generation doesn't occur with profit as the primary motive, as it's already not strictly profitable for the vast majority of people. As I have noted before in other threads, much generation is 'co-generation', allowing the user to put their computer to good use heating their living space, for people who do not have access to cheaper forms of heat than electro-resistive heating. Also, under your scenario, as others drop out for fear of an impossible difficulty, the odds that any one particular machine will find the next solution increases; so it's a self-regulating system. I can't say that no one will ever try it, but it's not going to break the network, and anyone who would try it is going to have to commit some serious resources simply to temporarily frustrate the network.
