Also, Tor Project has had v2 address depreciation on it's roadmap for 2 years now, they have given hidden service operators plenty of time to prime their community for the v2 --> v3 switch. This gradual change is way better than scrambling to depreciate v2 addresses in response to some state actor publicly breaking the RSA keys of v2 hidden services.
> I thought I owned my tor domain
You may now, but if v2 is kept around soon you won't be the only one with the domains private key.
What is the danger of exposing the hash of the services public key? Public keys are public anyway.
1. so little of the hash is exposed (only 80 bits of 160 for sha1), making it easier to find a collision
2. the hash is so weak (sha1 is widely considered broken), making it easier to find a collision
3. the underlying public key is so small, making it easier to derive the private key from the public key
IIRC if you find a collision you can use that to take over / contest an onion address, and obviously reversing the public key into a private key gives you as much control over an onion address as the original creator.
I personally don't like that v2 is being shut off instead of let run alongside v3. I thought I owned my tor domain I've been using the last decade but it's clear the tor project has the same amount of control as any registrar. I thought I could work on building a community like I have on the clear web but the tor project doesn't consider that a priority and will throw 15 years of history away to make sure non-technical users don't accidentally use v2 services. Tor is not really a place for community building. My mistake. I just won't use it anymore.