Onion routing is a system that provides secure and anonymous communication over the Internet. It works by sending data through a series of intermediate nodes, or “onion routers”, which each encrypt the data and forward it to the next node in the route. The data is encrypted multiple times, with each layer of encryption being added by the previous node in the route. When the data reaches its final destination, the layers of encryption are peeled away in reverse order, revealing the original data.

The main purpose of onion routing is to prevent the origin and destination of the data from being identified. By sending the data through multiple intermediate nodes, each of which can only identify the immediately preceding and following nodes in the route, it becomes impossible for anyone who does not control all of the nodes to determine the origin or destination. Additionally, each node only knows the immediately preceding and following nodes, making it difficult for any of the nodes to link the data to the origin and destination.

Onion routing is a powerful tool for securing data and protecting privacy. It is used by many organizations, including the Tor project, which provides an anonymous web browsing system. It is also used in many other applications, such as providing secure communications for military personnel and journalists in dangerous areas.