At 1/3 of a second to compute a single hash, brute forcing the entire space of possible addresses takes around 45 CPU-years. But computing the hash of every sin

At 1/3 of a second to compute a single hash, brute forcing the entire space of possible addresses takes around 45 CPU-years. But computing the hash of every single IP address is ridiculously parallel, so it's trivial to spin up 2k machines on EC2 and brute force the entire thing in a week. Total cost, somewhere under $8k if you don't want to bother owning real machines, less for any organization that happens to need to do similar things on a regular or semi-regular basis. It's not a trivial investment since that effort only gets you a single IP address, but it's easily within the reach of a vast number of organizations if they have real motivation (read: not a fishing expedition) to reverse it.