Post 5 of 6 on Anyhide. This post is about peer discovery and session setup over Tor.
There's a surprising amount of work between "I have a cryptographic protocol" and "two people can talk to each other." This post is about that work.
The protocol from Post 4 assumes Alice and Bob can send each other bytes. It does not explain how they find each other in the first place, how they agree on a session, or what happens when the network drops messages. For Anyhide's chat, the answer to all three questions involves Tor hidden services, and I'd never written a line of Tor code before starting.
I used arti-client, the Rust-native Tor implementation from the Tor Project. Most content about Tor integration assumes you're running tor as a separate daemon and talking to its SOCKS port. Arti is different: it's a library you embed directly. You get a real Tor client inside your process, running on your runtime, with circuits you can open and hidden services you can host.
It's also marked experimental by the Tor Project, which I'll come back to.
