Beware that the author mention this in the repository

> Please use sish, don't use my hack. The code is provided for research and archiving purposes only, it's bad because I abandoned it as soon as I found that this exact idea have been implemented already in sish. The code is non-portable.

Interesting, was thinking about quick and dirty solution of this kind to temporarily make something running on my laptop publicly available for tests/dev purposes ;)

How does it work under the hood? Can I share special private key/password between devices/users?

The right way to do this is IPv6.