A Tor Onion Service provides end-to-end encryption like the HTTPS connection.It also mixes up the traffic with lots of other traffic, so its not easy to see what traffic goes together.
That makes it a lot harder for a network observer to tell when a security update is being downloaded.
Additionally, using a Tor Onion Service forces the traffic over Tor, so that the Debian mirror server cannot see which server is requesting the updates. There are other benefits as well, besides just for the person running the high security server in this example, especially if all of the traffic is coming over Tor.
There is only a single Tor Onion Service for the main archive.
An alternate approach using the combination of Tor and as the package source means that your server will get updates from a different mirror each time Tor changes its exit node (I believe that’s every 10 minutes or so).
Here’s how to set up the apt sources to get packages and updates via Tor Onion Services without delaying security updates.
First, remove `/etc/apt/sources.list` and `/etc/apt/d/*.list` to start with a clean slate.
If you have that setup, then you can add the onion addresses as Debian apt sources as if they are any other HTTP Debian mirror.
Another option is to install `apt-transport-tor` like TAILS does, then you can use special syntax to add the Tor Onion Services.
The default Debian and Ubuntu package servers use plain HTTP with unencrypted connections.