I2P Proxies
What is I2P
I2P (Invisible Internet Project) is an anonymous overlay network designed for secure communication. I2P uses a unique technology called garlic routing, an evolution of the onion routing used in Tor.
Unlike Tor, which focuses on anonymous access to the regular internet, I2P is primarily designed for in-network services (eepsites). However, I2P can also be used as a regular proxy via outproxies.
Garlic Routing vs Onion Routing
Onion Routing (Tor)
Each message is encrypted in layers and sent separately along a chain of nodes. One packet — one circuit.
Garlic Routing (I2P)
Multiple messages are bundled into a single "garlic clove" and sent together. This:
- Makes traffic analysis more difficult (it's unclear how many messages are in the packet)
- Increases efficiency (less overhead)
- Allows reply instructions to be included in the same packet
I2P Architecture
Tunnels
I2P builds unidirectional tunnels:
- Outbound tunnel — for sending data
- Inbound tunnel — for receiving data
Each tunnel consists of 1-3 hops. Separate tunnels for sending and receiving enhance anonymity — compromising one tunnel does not reveal both directions.
Floodfill Routers
Special nodes that store information about the network database (netDb) — the equivalent of DNS for I2P.
LeaseSet
A set of "entry points" (input tunnels) for each I2P service. The client retrieves the LeaseSet from netDb and connects to the service.
I2P as a Proxy
Outproxies
An outproxy is an I2P node that forwards traffic to the regular internet. It's analogous to an exit node in Tor, but there are significantly fewer of them in I2P.
Through an outproxy, you can access regular websites, hiding your IP behind a chain of I2P tunnels.
Outproxy Limitations
- Very few available outproxies (a handful)
- Speed is even lower than in Tor
- No guarantee of availability
- The outproxy operator sees your traffic (if HTTP without TLS)
- Not designed for mass use
Eepsites (Hidden Services)
The primary use of I2P is access to internal services (.i2p domains). Services are completely hidden within the network.
I2P vs Tor
| Parameter | I2P | Tor |
|---|---|---|
| Routing | Garlic (packet-based) | Onion (stream-based) |
| Tunnels | Unidirectional | Bidirectional |
| Focus | In-network services | Exit to regular internet |
| Outproxies/Exit nodes | Few | Thousands |
| Speed | Very low | Low |
| Hidden services | Eepsites (.i2p) | Onion services (.onion) |
| Protocol | UDP (SSU) + TCP (NTCP2) | TCP |
| DPI resistance | High | Medium (bridges help) |
Advantages of I2P
1. Packet-based Routing
UDP transport is better suited for latency-sensitive applications and more resistant to blocking.
2. Unidirectional Tunnels
Separate paths for sending and receiving — harder to analyze traffic.
3. Garlic Bundling
Bundling packets complicates correlation analysis.
4. DPI Resistance
The I2P protocol is harder to identify and block at the ISP level.
5. Fast Tunnel Rotation
Tunnels are recreated every 10 minutes, hindering long-term monitoring.
Disadvantages
1. Very Small Scale
Around 50,000 active routers (vs hundreds of thousands for Tor). Fewer nodes mean less anonymity.
2. Almost Impossible to Use as an HTTP Proxy
Few outproxies, low speed, unreliability.
3. Complex Setup
Requires running a Java router, waiting for network integration (bootstrap), and configuring tunnels.
4. Java Dependency
The main implementation is written in Java — consumes a lot of resources.
5. Limited Documentation and Community
Compared to Tor, I2P's documentation and support are significantly scarcer.
When to Use I2P
Suitable for:
- Accessing eepsites and I2P hidden services
- Anonymous communication (email, chat) within I2P
- File sharing (I2P Snark — anonymous BitTorrent)
- Experimenting with anonymous networks
Not suitable for:
- Proxying for access to regular websites (no proper outproxies)
- Parsing and automation
- Any tasks requiring speed
- Everyday browsing
Conclusion
I2P is a specialized anonymous network with unique technical solutions (garlic routing, unidirectional tunnels). As a proxy for accessing the regular internet, it significantly lags behind Tor due to the small number of outproxies and low speed. The main value of I2P lies in its own ecosystem of hidden services and high-level anonymity for in-network communication.