Most of us know of Tor V2 addresses (16 characters) and Tor V3 addresses (56 characters).
What about Tor V1 addresses?
What was its specification or why wasn't it used much or at all?
Example:
Clearnet: https://www.whonix.org/
V1 Address: ???
V2 Address: http://kkkkkkkkkk63ava6.onion
V3 Address: http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion
It would seem that the v1 Rendezvous Specification was only ever partially implemented. tor could understand and accept v1 descriptors at one point, but never generated them.
There was however a v0 Rendezvous Specification that used a binary descriptor format. That format was deprecated in tor 0.2.2.1-alpha. From what I can tell from the specification document, the addresses for v0, v1 and v2 onion services all looked alike.
You may also be interested to know that before .onion addresses existed, there were .exit addresses that could be used to access a service via a particular exit relay. This meant that an exit relay could host a service that wasn't on the public Internet and could only be accessed via Tor. There were a number of issues with this approach however and it was disabled in tor 0.2.2.1-alpha.
