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GNUnet is a mesh routing layer for end-to-end encrypted networking and a framework for distributed applications designed to replace the old insecure Internet protocol stack.
In other words, GNUnet provides a strong foundation of free software for a global, distributed network that provides security and privacy. Along with an application for secure publication of files, it has grown to include all kinds of basic applications for the foundation of a GNU internet.
Security and privacy are virtually non-existant on today's Internet. Most security protocols rely on some "trusted" third parties (such as certificate authorities), which are frequently compromised. Traffic on the Internet is routed and thus controlled by large providers, and easily censored (or blocked entirely) at national borders. The originally decentralized web is increasingly assimilated into services hosted at large advertising companies that mine it for private information to be sold to advertisers. In all of these domains, economics drives the creation of mega-corporations, which in turn has enabled mass surveillance by authoritarian institutions.
GNUnet's goal is to offer a way out of hierarchical networking, transitioning into a network of equals. As each participant contributes a small amount of resources to the common, GNUnet does not require users to give up their privacy in order to use the network. In particular, peer-to-peer networks do not need advertising revenue or other profits to function. However, merely decentralizing the Internet is not sufficient, we also need security and privacy. In fact, for individuals, privacy tends to be more important among peers than vis-a-vis a faceless mega-corporation. Thus, GNUnet's focus is on providing security while remaining fully decentralized.
GNUnet is extensible and makes it easy to build new (peer-to-peer) applications, or add alternative network transports to the base system. GNUnet is not a classical overlay network, as GNUnet does not need TCP/IP to function: while GNUnet peers can operate over classic Internet protocols like TCP or UDP, they can also exchange information directly, for example over WLAN or Bluetooth, without using IP at all.
GNUnet is not just an implementation effort, but also a research project. Unlike many other research projects, our goal is to provide a working, production-quality system (but we are not there yet). Providing security and privacy in a fully decentralized setting is difficult, as many security construction assume some kind of trusted third party. Furthermore, as GNUnet is an open network, an adversary can actively participate. A strong adversary might be able to run many peers, possibly even the majority of the peers. At this point, even expensive security protocols that involve majorities fail. We note that GNUnet does not have one "global" security model for all of its applications; for that, our applications are too diverse in their designs and requirements. However, we always build our components under the assumption that there
are active, malicious participants in the network.
Many of the key technical contributions behind GNUnet are described in detail in our research papers. The following sections will briefly sketch some of the key ideas for some of GNUnet's flagship applications.
Key ideas behind GNUnet's anonymous file-sharing application include an improved content encoding (ECRS, the encoding for censorship resistant sharing) and a new protocol for anonymous routing (gap). In gap, anonymity is provided by making messages originating from a peer indistinguishable from messages that the peer is routing. All peers act as routers and use link-encrypted connections with stable bandwidth utilization to communicate with each other. Properties of the content encoding and the routing protocol allow GNUnet to reward contributing peers with better service using an excess-based economic model for resource allocation. As a result, peers in GNUnet monitor each others behavior with respect to resource usage; peers that contribute to the network are rewarded with better service.
The GNU Name System (GNS) is a fully decentralized and censorship-resistant public key infrastructure. Names in GNS are personal, as each user is in full control of his ".gnu" zone. Users can delegate subdomains to the namespaces of other users, and resolve each other's names using a privacy-preserving, censorship-resistant secure network lookup mechanism. GNS is interoperable with DNS, and can be used as an alternative to the X.509 PKI or the Web-of-Trust.
Using GNS for identity management, we are currently starting to build the foundation for fully decentralized social networking with SecuShare. Key design goals include never storing (or transmitting) unencrypted data at third parties, and the use of the PSYC protocol for semantic extensibility, that is, to allow smooth migration of data to new revisions of the protocol. SecuShare is still in its infancy, while we have worked out large parts of the design much more code will need to be written before it can be used. Help is very welcome. You can find additional details on the Secushare.org website.
GNUnet continues to expand in scope and improve both in terms of technical ideas and implementation, often thanks to discussions with developers from related projects, such as Tor or I2P. We collaborate with these (and many other) projects whenever it makes technical sense, as we share the same ideals and goals: secure, private networking using free software to safeguard a free and open society.
While we believe that GNUnet is (or at least will become) the best solution for (anonymous) file-sharing, GNUnet is much more than this. Our developers have the ambition to provide a good general infrastructure for developing a wide range of new decentralized networking applications, possibly to the point of replacing the Internet as it is known today with a GNU network that embodies the ideals of the GNU project.
However, certain applications are not within the scope of the GNUnet project. In particular, users that are looking for faster, non-anonymous file-sharing or to anonymize their HTTP traffic should probably look elsewhere, as our goal is not to duplicate existing applications.