I2P (Invisible Internet Project)

I2P, the Invisible Internet Project, is a free, open-source anonymity network built as a self-contained overlay on top of the regular internet. Where Tor is oriented toward anonymously reaching the public web through exit relays, I2P is designed primarily for anonymous services that live entirely inside the network — analogous to Tor's onion services but as the default mode rather than a special case.

Garlic routing

I2P uses a variant of onion routing called garlic routing. Instead of encrypting a single message in layers, it can bundle several messages ("cloves") together inside one encrypted package, which complicates traffic analysis. Its tunnels are also unidirectional: data travels to a destination along one path and returns along a different one. Because the outbound and inbound paths differ, an observer who watches one direction learns less about the full conversation than they would on a bidirectional Tor circuit.

How it compares

I2P is fully peer-to-peer — every participant typically also relays traffic for others, which strengthens the network as it grows and avoids a fixed set of well-known exit points. This makes it well suited to long-lived hidden services, file sharing, and distributed applications, but a weaker fit for casually reaching ordinary websites, since outproxies (its equivalent of exit nodes) are few. For a sovereign operator, I2P is a second, independent anonymity layer to evaluate alongside Tor, valuable precisely because it fails differently.

Compare with Tor (The Onion Router) and Onion Service (.onion), and weigh which network fits your needs using a clear Threat Model.