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I2P Compared to Tor and Freenet

There are a great many other applications and projects working on anonymous communication and I2P has been inspired by much of their efforts. This is not a comprehensive list of anonymity resources - both freehaven's Anonymity Bibliography and GNUnet's related projects serve that purpose well. That said, a few systems stand out for further comparison. The following are discussed on this page:

The following are discussed on the other networks page:

The content of this page is subject to update, discussion and dispute, and we welcome comments and additions. You may contribute an analysis by entering a new ticket on trac.i2p2.de.

Tor / Onion Routing

[Tor] [Onion Routing]

Tor and Onion Routing are both anonymizing proxy networks, allowing people to tunnel out through their low latency mix network. The two primary differences between Tor / Onion-Routing and I2P are again related to differences in the threat model and the out-proxy design (though Tor supports hidden services as well). In addition, Tor takes the directory-based approach - providing a centralized point to manage the overall 'view' of the network, as well as gather and report statistics, as opposed to I2P's distributed network database and peer selection.

The I2P/Tor outproxy functionality does have a few substantial weaknesses against certain attackers - once the communication leaves the mixnet, global passive adversaries can more easily mount traffic analysis. In addition, the outproxies have access to the cleartext of the data transferred in both directions, and outproxies are prone to abuse, along with all of the other security issues we've come to know and love with normal Internet traffic.

However, many people don't need to worry about those situations, as they are outside their threat model. It is, also, outside I2P's (formal) functional scope (if people want to build outproxy functionality on top of an anonymous communication layer, they can). In fact, some I2P users currently take advantage of Tor to outproxy.

Comparison of Tor and I2P Terminology

While Tor and I2P are similar in many ways, much of the terminology is different.
TorI2P
CellMessage
ClientRouter or Client
CircuitTunnel
DirectoryNetDb
Directory ServerFloodfill Router
Entry GuardsFast Peers
Entry NodeInproxy
Exit NodeOutproxy
Hidden ServiceEepsite or Destination
Hidden Service DescriptorLeaseSet
Introduction pointInbound Gateway
NodeRouter
Onion ProxyI2PTunnel Client (more or less)
RelayRouter
Rendezvous Pointsomewhat like Inbound Gateway + Outbound Endpoint
Router DescriptorRouterInfo
ServerRouter

Benefits of Tor over I2P

Benefits of I2P over Tor

Other potential benefits of I2P but not yet implemented

...and may never be implemented, so don't count on them!

Freenet

[Freenet]

Freenet is a fully distributed, peer to peer anonymous publishing network, offering secure ways to store data, as well as some approaches attempting to address the loads of a flash flood. While Freenet is designed as a distributed data store, people have built applications on top of it to do more generic anonymous communication, such as static websites and message boards.

Compared to I2P, Freenet offers some substantial benefits - it is a distributed data store, while I2P is not, allowing people to retrieve the content published by others even when the publisher is no longer online. In addition, it should be able to distribute popular data fairly efficiently. I2P itself does not and will not provide this functionality. On the other hand, there is overlap for users who simply want to communicate with each other anonymously through websites, message boards, file sharing programs, etc. There have also been some attempts to develop a distributed data store to run on top of I2P, (most recently a port of Tahoe-LAFS) but nothing is yet ready for general use.

However, even ignoring any implementations issues, there are some concerns about Freenet's algorithms from both a scalability and anonymity perspective, owing largely to Freenet's heuristic driven routing. The interactions of various techniques certainly may successfully deter various attacks, and perhaps some aspects of the routing algorithms will provide the hoped for scalability. Unfortunately, not much analysis of the algorithms involved has resulted in positive results, but there is still hope. At the very least, Freenet does provide substantial anonymity against an attacker who does not have the resources necessary to analyze it further.