The Onion Router (Tor) network is a decentralized protocol which uses onion routing to enable private and censorship-resistant digital interaction. The Tor network enables citizens to bypass censorship and oppression from governments and for digital black markets to sell goods and services prohibited by governments.
Tor is used for a wide variety of activities, both legal and illegal. Tor was used by Edward Snowden to safely alert the world of the US National Security Agency’s espionage programs. Tor was used by activists in the Arab Spring and is used by dissidents around the world today. Tor was also used by Ross Ulbricht to host the Silk Road, a Bitcoin-powered marketplace.
The Bitcoin Network and the Lightning Network are both capable of operating over the Tor Network as well, in order to preserve the privacy of those who run Bitcoin or Lightning nodes. In many ways, the Lightning Network is similar to the Tor network. Whereas Tor enables onion routing of information, Lightning enables onion routing of bitcoin.
Like other decentralized networks, including Bitcoin, Tor is composed of nodes which connect and serve one another content, including websites and files. Tor differs from the regular internet because users do not connect directly to the website they are accessing. Instead, Tor users access their content via a series of other nodes, preserving their privacy and anonymity.
For example, if Alice wants to access Google.com over the Tor network, Alice would send an encrypted request to a Tor node. This Tor node, which we will call B, cannot read Alice’s request, but will instead pass the request along to another Tor node C. Node C will then serve Alice’s message to Google.com and return an encrypted response to node B, who will forward the response to Alice.
This process is more convoluted than the traditional internet, but affords Tor users superior privacy.