What is Tor?
A free network that hides where internet traffic comes from by relaying it through three volunteer-run computers. Bitcoin nodes can use it.
Tor, short for The Onion Routing, relays each connection through three computers run by volunteers and encrypts it at every step. The aim, in the Tor Project’s words, is connections that “don’t reveal who is talking to whom”. Websites can also run as onion services, with addresses ending in .onion, which hide where their own computers are.
Bitcoin Core can connect to other nodes through Tor and run as an onion service itself, which hides the node’s own internet address. Tor hides where a connection comes from, not what is in the blockchainBlockchainBitcoin's shared record of every payment since 2009, stored in blocks that each link to the one before — which is what makes it a chain.: payments stay public however they reach the network.
Onion routing began at the US Naval Research Laboratory in 1995, and the Tor Project, which develops Tor, became a non-profit in 2006. Silk Road, the drug market the FBI shut down in 2013, ran as an onion service.
References
- The Tor Project, “Tor Project home page”.
- The Tor Project, “History”.
- The Tor Project, “Onion services”.
- Bitcoin Core, “Tor support in Bitcoin”.