knowledge/technology/internet/Tor.md

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The Onion Router (TOR)

The Tor Project (The onion routing) is an open source implementation of onion routing that provides free access to an anonymous proxy network. Its primary goal is to enable online anonymity by protecting against traffic analysis attacks.

Users of the Tor network run an onion proxy software on their machines, which presents a SOCKS interface to its clients. This software connects out to Tor, periodically negotiating a virtual circuit through the Tor network. Tor employs cryptography in a layered manner (hence the 'onion' analogy), ensuring forward secrecy between routers.

As an overlay network it is similiar to i2p.

Usage

Start/enable tor.service. Alternatively, launch it with sudo -u tor /usr/bin/tor.

To use a program over Tor, configure it to use 127.0.0.1 or localhost as a SOCKS5 proxy, with port 9050 for plain Tor with standard settings.

The proxy supports remote DNS resolution: use socks5**h**://localhost:9050 for DNS resolution from the exit node (instead of socks5 for a local DNS resolution).

Configuration

Tor reads its configurations from the file /etc/tor/torrc by default, or if the latter is not found, from $HOME/.torrc. The configuration options are explained on the Tor website. The default configuration should work fine for most Tor users.

Hidden Services

Hidden Services are web services behind an onion domain.
To generate onion domains mkp224o can be used.

To enable a hidden service add this to torrc:

HiddenServiceDir /var/lib/tor/hidden_service/
HiddenServicePort 80 127.0.0.1:80