Definition:
Tor is a network and a set of software tools designed to improve the privacy of internet communications. They route traffic through several servers, called nodes or relays, to make it harder to link the origin of a connection with its destination.
Its name comes from The Onion Router and refers to layered encryption, similar to the layers of an onion. Tor Browser is the browser configured to use this network; the network and the browser are distinct components.
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History and evolution of Tor
Onion routing emerged from research at the United States Naval Research Laboratory during the 1990s. Its goal was to develop communications that made it harder to identify who was connecting to whom.
Roger Dingledine, Nick Mathewson and Paul Syverson participated in Tor’s development. The network began deployment in 2002 and its code was released under a free software licence. In 2006, The Tor Project was established as a nonprofit organisation to maintain its development.
Development of Tor Browser began in 2008 and made the network more accessible without requiring users to configure a conventional browser separately. The project brings together paid staff, researchers and a community of contributors and relay operators.
Main features of Tor
The network and the project’s tools provide different functions:
- Distributed routing: traffic passes through several relays operated by different entities, rather than relying on a single intermediary to manage the entire connection.
- Layered encryption: the client prepares traffic so that each relay processes its corresponding layer. Relays do not all receive the same information about the route.
- Browser protections: Tor Browser includes measures to limit cross-site tracking and reduce the differences that make it possible to recognise a browser through its fingerprint.
- Onion services: it enables access to services with .onion addresses within the network itself. These are not equivalent to the entire deep web, which also includes unindexed content unrelated to Tor.
- Censorship circumvention tools: bridges and other connection mechanisms can help when direct access to the network is blocked. Their effectiveness depends on the restrictions in place.
- Application integration: Tor software provides a SOCKS interface for compatible applications. They require appropriate configuration; installing Tor does not automatically route all device traffic through its network.
How Tor works
For a typical connection to a website on the conventional web, Tor builds a circuit with three relays: entry, middle and exit. Selection follows the software’s criteria; it is not simply a matter of choosing three servers at random.
The entry relay knows the client’s IP address, but does not directly receive the final destination. The middle relay connects adjacent relays. The exit relay connects to the destination server, which sees the exit relay’s IP address rather than the user’s original address.
Each relay removes its corresponding layer of encryption. This design separates knowledge of the origin and destination across different points in the network, but does not guarantee protection against every analysis that correlates traffic at both ends.
Tor encryption does not replace HTTPS on the conventional web. Without HTTPS, the connection between the exit relay and the website can carry unencrypted content. Onion services use a different connection mechanism within Tor, without an exit relay to the public web.
Advantages of using Tor
Tor can reduce exposure of the originating IP address to websites visited and make certain forms of connection surveillance more difficult. It can also facilitate access to blocked information and allows services to be published without directly exposing their server’s location.
Its open-source code allows the software’s operation to be examined. The diversity of operators distributes trust among several participants, although neither characteristic guarantees absolute security on its own.
These advantages have limitations: browsing can be slower, some websites restrict connections from Tor and the network does not protect against a compromised device. Signing in or providing personal information allows a service to identify a user even if it does not know their original IP address.
Unlike private browsing, Tor changes the route of the connection. It does more than limit the history and data that the browser retains on the device.
Common use cases of Tor
Journalists and human rights organisations can use Tor to access information or communicate with sources while reducing the exposure of their connections. Users on censored networks can use it to access services unavailable through a direct connection.
Researchers and organisations can also consult public resources without revealing their work network’s IP address to the destination. Onion services allow websites and other resources to be hosted within Tor, including communication and document submission systems.
These uses do not make Tor an infallible anonymity system or a tool exclusively for the dark web. Protection depends on the application used, its configuration and the information shared during the connection.