Introduction to Tor vs I2P

Darknet. The very word itself evokes the shadowy side of the internet—a virtual red-light district, a digital alleyway, and a ghetto all in one. Despite the media and various governments trying to imprint this ominous image into public consciousness, individuals who are conscious of their privacy understand that in today's world—where ISPs store data in petabytes and where both governments and the private sector deploy massive supercomputing resources for traffic analysis—people must take the protection of anonymous information access and communication freedom into their own hands. Two of the most popular tools for this purpose on the internet are Tor and I2P. Below, we compare and analyze these technologies.

Tor

First, let's examine the underlying technology of the Tor network and how it protects your anonymity online. The Tor network consists of three types of nodes: directory servers, exit nodes (also called exit relays), and internal relays. When you connect to Tor, the first step is for your client to request an up-to-date list of relays from one of the trusted directory servers. The addresses of these servers are included in the default configuration files shipped with the client (of course, as with any reliable privacy tool, you can modify which directory servers you trust).

Once your client has downloaded the active relay list, it determines the optimal route for your traffic within the Tor network, ultimately ending at an exit node. The established route consists of your computer, the first relay, multiple internal relays, and finally, the exit node. This differs significantly from traditional IP packet forwarding, which occurs dynamically between routers on the internet. In traditional IP routing, each packet is forwarded along the best available path at that moment, with no “fixed” connection from the network’s perspective. In contrast, Tor maintains a predefined route for the entire session.

When the channel is established, your client exchanges cryptographic keys with the first node and starts sending encrypted data traffic. The data passed through intermediary relays is wrapped in additional encryption layers at each step, using the relays' own keys. This layered encryption approach is called "onion routing," which is the core technology behind Tor. The data stream is finally decrypted at the exit relay before being forwarded to the regular internet. This mechanism ensures anonymous browsing—exit nodes process traffic from many Tor users simultaneously, making individual user traffic indistinguishable within a larger data flow.

It's important to highlight that an exit node only knows which intermediary relay it received data from (this applies to every relay in the chain). This means that your identity and online activity are cryptographically separated: The entry node knows who you are, but not what you are doing. The exit node knows what you are doing, but not who you are. The intermediate relays only see encrypted data being passed between nodes. As long as your traffic content does not reveal any identifiable information, Tor allows you to browse the internet completely anonymously.

As a side note, Tor also enables "hidden services"—web services that are accessible only within the Tor network. While this is not Tor’s primary goal, it allows users to host and access services securely and anonymously. These services include blogs, email servers, and forums. Later, we will see that I2P offers a more efficient solution for running hidden services, but for those primarily interested in anonymous access to traditional web content, Tor is an indispensable tool.

I2P

At first glance, I2P offers many of the same benefits as Tor. Both allow anonymous access to online content, both use a peer-to-peer-like routing structure, and both employ layered encryption. However, I2P was designed with fundamentally different goals in mind.

As we saw earlier, Tor’s primary function is to provide anonymous access to the open internet, while hidden services are a secondary feature. I2P, on the other hand, was designed from the start as a true darknet. Its core function is to create a "network within a network," where traffic remains inside the system. The I2P network contains very few external exit points, and these are rarely accessible.

Unlike Tor, I2P uses packet-based routing rather than circuit-based routing. This allows I2P to dynamically avoid network congestion and service outages—similar to how the internet’s standard IP routing works. This approach provides greater reliability and redundancy. Additionally, I2P does not rely on trusted directory servers to obtain route information. Instead, routes are continuously and dynamically updated, and each router evaluates the performance of other routers, sharing results within the network.

Furthermore, I2P establishes two separate one-way (simplex) tunnels for each communication path, whereas Tor uses a single two-way (duplex) circuit. This means that even if an attacker intercepts traffic within the network, only one direction of the communication can be observed, which significantly enhances anonymity.

At the application level, I2P also operates differently from Tor. Tor provides a local proxy, which your applications must use (or you need to download pre-configured software packages). I2P, on the other hand, is designed for applications built specifically for the I2P network. Examples include instant messaging systems, file-sharing services, email networks, and distributed storage solutions (such as I2P’s encrypted cloud storage, similar to Freenet).

Summary

Both Tor and I2P provide cryptographically secure methods for anonymous information access and online communication. However, their strengths lie in different areas: Tor excels at providing anonymous access to the open internet, I2P is a more stable and resilient darknet—a true network within a network.

It is important to keep in mind, however, that regardless of which tool one uses, their Internet Service Provider (ISP) can detect that they are using Tor or I2P (although it cannot determine the content of the traffic).