I've recently been trying to upgrade my tor setup and that means version 3 addresses using curve25519 56 char hashes. As of right now there are no GPU implementations for mining. That means CPU mining and it's really slow. Maxing out an i5 3570k it would take about 2 weeks (on average) to brute force a superkuh* prefix. But I don't want to only do that for two weeks so I'm throwing it on my fanless 5w Celeron N3150 which I *can* let run for as long as I want quitely. With it's hash rate it should take about 2 months. But it's random and could take much more or less.
There are some alternative cryptocoins out there that use the same curve25519 algorithm which have opencl GPU implementations but who knows (not me) how one would adapt the opencl bits for tor v3 addresses. https://github.com/PlasmaPower/nano-vanity. The real vanity here is thinking I can poke at this crap and get it to work. I can't. I'll just have to wait the 2+ months.
Update! It only took 5 days. Lucky me. superkuhf6grlngvhaelkgaem6i4phmzd7rekeguphwbplhk3fanpjqd.onion here I come.