Tor
The core principle of Tor, Onion routing, was developed in the mid-1990s by United States Naval Research Laboratory employees, mathematician Paul Syverson, and computer scientists Michael G. Reed and David Goldschlag, to protect U.S. communications online. Onion routing is implemented by encryption in the application layer of the communication protocol stack, nested like the layers of an onion. The alpha version of Tor, developed by Syverson and computer scientists Roger Dingledine and Nick Mathewson and then called The Onion Routing project (which later simply became “Tor”, as an acronym for the former name, was launched on 20 September 2002. The first public release occurred a year later.
In 2004, the Naval Research Laboratory released the code for Tor under a free license, and the Electronic Frontier Foundation (EFF) began funding Dingledine and Mathewson to continue its development. In 2006, Dingledine, Mathewson, and five others founded The Tor Project, a Massachusetts-based 501(c)(3) research-education nonprofit organization responsible for maintaining Tor. The EFF acted as The Tor Project’s fiscal sponsor in its early years, and early financial supporters of The Tor Project included the U.S. Bureau of Democracy, Human Rights, and Labor and International Broadcasting Bureau, Human Rights Watch, the University of Cambridge, and Google.
Over the course of its existence, various Tor attacks and weaknesses have been discovered and occasionally used. Attacks against Tor are an active area of academic research.