onion router

The researchers wanted to find a way to do the seemingly impossible — to give the military the benefits of a global, high-speed communications network without exposing them to the vulnerabilities of the metadata that the network relied on to operate.Enter Onion routing. Onion routing has undergone many changes and refinements over the years, but the basic principle has remained the same: The routing information used to navigate the internet is first hidden under three layers of encryption, like a Russian doll. It is from these layers that onion routing gets its name. This “onion” of routing information is then sent into a network of onion routers: servers, or relays, located around the world that bounce the traffic around and between themselves. Each of these relays decrypts a layer of encryption to reveal the address of the next server in the network, until the final server reveals the destination of the traffic and makes a connection to the target web service. None of them can see both the origin and the destination of the traffic.

The Secret History of Tor: How a Military Project Became a Lifeline for Privacy The MIT Press Reader 2025