In July 2020, the Tor Project released the timeline for the depreciation of version two onion services (v2) in favor of the more secure version three onion services (v3). By October 16, 2021, the short onion services will no longer functionally exist.
The Tor Project is forcing the transition from v2 onion services to onion services for the sole purpose of safety, according to a tor talk message from David Goulet:
Onion service v2 uses RSA1024 and 80 bit SHA1 (truncated) addresses. It also
still uses the TAP handshake which has been entirely removed from Tor for many years now except v2 services. Its simplistic directory system poses to a variety of enumeration and location-prediction attacks that give HSDir
relays too much power to enumerate or even block v2 services. Finally, v2
services are not being developed nor maintained anymore. Only the most severe security issues are being addressed.
As described in the Tor Project’s blog post, onion service operators have had years to transition their users and infrastructure to v3 onion services. The Tor Project does anticipate difficulties though.
The decision to shift to v3s made sense from a security perspective as outlined by the Tor Project. Many users disagreed, arguing in the announcement’s comment section about the merits if the change. One user wrote that the Tor Project “misunderstood” the nature of open source software by preventing Tor users from using outdated and insecure software. A different user responded to the commenter described above by explaining how users with such an outrageous mindset could technically still use v2s:
“…[Y]ou’re welcome to download the Tor source code and add v2 functionality back in, and you’ll be able to visit sites hosted by people who have done the same. No one is stopping you. If your favorite sites no longer host a v2 (with a patched Tor), then you’ll have to convince them to do so. If you can’t convince them, then, well, maybe v2 isn’t really so important after all.”
It is also commonly accepted that v2 onions are objectively more aesthetically pleasing. The fact that v3s are a monstrosity to look at likely causes some of the resistance.
Nevertheless, the October kill date is only months away.