Freenet is free software which lets you anonymously share files, browse and publish “freesites” (web sites accessible only through Freenet) and chat on forums, without fear of censorship. Freenet is decentralised to make it less vulnerable to attack, and if used in “darknet” mode, where users only connect to their friends, is very difficult to detect.
Communications by Freenet nodes are encrypted and are routed through other nodes to make it extremely difficult to determine who is requesting the information and what its content is.
Users contribute to the network by giving bandwidth and a portion of their hard drive (called the “data store”) for storing files. Files are automatically kept or deleted depending on how popular they are, with the least popular being discarded to make way for newer or more popular content. Files are encrypted, so generally the user cannot easily discover what is in his datastore, and hopefully can’t be held accountable for it. Chat forums, websites, and search functionality, are all built on top of this distributed data store.
Freenet has been downloaded over 2 million times since the project started, and used for the distribution of censored information all over the world including countries such as China and the Middle East. Ideas and concepts pioneered in Freenet have had a significant impact in the academic world. Our 2000 paper “Freenet: A Distributed Anonymous Information Storage and Retrieval System” was the most cited computer science paper of 2000 according to Citeseer, and Freenet has also inspired papers in the worlds of law and philosophy. Ian Clarke, Freenet’s creator and project coordinator, was selected as one of the top 100 innovators of 2003 by MIT’s Technology Review magazine.
An important recent development, which very few other networks have, is the “darknet”: By only connecting to people they trust, users can greatly reduce their vulnerability, and yet still connect to a global network through their friends’ friends’ friends and so on. This enables people to use Freenet even in places where Freenet may be illegal, makes it very difficult for governments to block it, and does not rely on tunneling to the “free world”.
Freenet network:
The network consists of a number of nodes that pass messages among themselves. Typically, a host computer on the network runs the software that acts as a node, and it connects to other hosts running that same software to form a large distributed network of peer nodes. Some nodes are end user nodes, from which documents are requested and presented to human users. Other nodes serve only to route data. All nodes communicate with each other identically — there are no dedicated “clients” or “servers”. It is not possible for a node to rate another node except by its capacity to insert and fetch data associated with a key. This is unlike most other P2P networks where node administrators can employ a ratio system, where users have to share a certain amount of content before they can download.
Freenet may also be considered a small world network.
The Freenet protocol is intended to be used on a network of complex topology, such as the Internet (Internet Protocol). Each node knows only about some number of other nodes that it can reach directly (its conceptual “neighbors”), but any node can be a neighbor to any other; no hierarchy or other structure is intended. Each message is routed through the network by passing from neighbor to neighbor until it reaches its destination. As each node passes a message to a neighbor, it does not know or care whether the neighbor will forward the message to another node, or is the final destination or original source of the message. This is intended to protect the anonymity of users and publishers.
Each node maintains a data store containing documents associated with keys, and a routing table associating nodes with records of their performance in retrieving different keys.
This summary was written using the following sources:
[1] Freenet homepage
[2] Freenet papers
[3] Freenet wikipedia